[PATCH v7 00/18] Implement DWARF modversions

[PATCH v7 00/18] Implement DWARF modversions

[Sami Tolvanen]

Hi,

Here's v7 of the DWARF modversions series. The main motivation is
modversions support for Rust, which is important for distributions
like Android that are about to ship Rust kernel modules. Per Luis'
request [1], v2 dropped the Rust specific bits from the series and
instead added the feature as an option for the entire kernel to
make it easier to evaluate the benefits of this approach, and to
get better test coverage. Matt is addressing Rust modversion_info
compatibility issues in a separate patch set [2] that depends on
this series, and actually allows modversions to be enabled with
Rust.

Short background: Unlike C, Rust source code doesn't have sufficient
information about the final ABI, as the compiler has considerable
freedom in adjusting structure layout, for example, which makes
using a source code parser like genksyms a non-starter. Based on
earlier feedback, this series uses DWARF debugging information for
computing versions. DWARF is an established and a relatively stable
format, which includes all the necessary ABI details, and adding a
CONFIG_DEBUG_INFO dependency for Rust symbol versioning seems like a
reasonable trade-off as most distributions already enable it.

The first 15 patches add gendwarfksyms, a tool for computing symbol
versions from DWARF. When passed a list of exported symbols and
object files, the tool generates an expanded type string for each
symbol and computes symbol versions. gendwarfksyms is written in C,
uses libdw to process DWARF, and zlib for CRC32. Patch 16 ensures
that debugging information is present where we need it, patch 17
adds gendwarfksyms as an alternative to genksyms, and the last patch
adds documentation.

v7 is based on 6.13-rc3, and for your convenience, the series is
also available here:

https://github.com/samitolvanen/linux/commits/gendwarfksyms-v7

If you also want to test the series with actual Rust modules, this
branch adds Matt's latest modversion_info series:

https://github.com/samitolvanen/linux/commits/rustmodversions-v7

Sami


[1] https://lore.kernel.org/lkml/ZnIZEtkkQWEIGf9n@bombadil.infradead.org/
[2] https://lore.kernel.org/linux-modules/20241123-extended-modversions-v10-0-0fa754ffdee3@google.com/

---

v7:
- Added a Kconfig description to actually allow build testing each
  patch. (Patch 1)

- Added a MAINTAINERS entry for gendwarfksyms. (Patch 1)

- Cleaned up includes and fixed a build issue with asprintf not
  always being present without _GNU_SOURCE. (Patches 1, 11, and 13)

- Adjusted hash table sizes for lower overhead as we're not right
  now concerned with processing vmlinux.o, and thus need to deal
  with a smaller number of symbols. (Patches 1, 4, 9, 11, and 13)

- Added error handling for gelf_getsymshndx failures. (Patch 2)

- Renamed the is_declaration function to is_kabi_definition for
  clarity and reversed the logic per Petr's suggestion. (Patch 9)

- Dropped the redundant default Kconfig tag. (Patch 17)

- Fixed a documentation typo. (Patch 18)

v6: https://lore.kernel.org/lkml/20241121204220.2378181-20-samitolvanen@google.com/
- Dropped pointer expansion limits as this affects version
  stability when exported symbols are removed. (Patch 9)

- Changed local type definitions (in .c files) that are opaque
  to external users to be treated as declarations even if a
  definition is available. (Patch 9)

- Switched to zlib's CRC32 implementation per Masahiro's
  suggestion. (Patch 12)

- Renamed struct_declonly kABI rule to simply declonly, as it
  applies also to unions and enums, added a new rule for
  overriding enumerator values, and refactored the examples.
  (Patch 13)

- Added --stable support for renamed structure members and
  also added examples. (Patch 14)

- Rebased on linux-kbuild/for-next for Masahiro's symtypes
  build rule clean-ups. (Patch 17)

- Updated the documentation reflect --stable changes. (Patch 18)

v5: https://lore.kernel.org/lkml/20241030170106.1501763-21-samitolvanen@google.com/
- Rebased on v6.12-rc5.

- Fixed an issue with limiting structure expansion, and applied
  Petr's clean-up. (Patch 10)

- Dropped an unnecessary return statement in error path. (Patch
  12)

- Addressed several other smaller issues Petr brought up. (Patches
  13, 14, and 15)

- Added a KBUILD_GENDWARFKSYMS_STABLE flag to enable --stable for
  the entire kernel build. (Patch 18)

- Updated documentation to include KBUILD flags. (Patch 19)

- Picked up Reviewed-by tags from v4.

v4: https://lore.kernel.org/lkml/20241008183823.36676-21-samitolvanen@google.com/
- Rebased on v6.12-rc2, which now includes all the prerequisites.

- Dropped unnecessary name_only parameter for symbols.c::for_each
  and cleaned up error handling. (Patch 3)

- Fixed anonymous scope handling to ensure unnamed DIEs don't get
  names. (Patch 4)

- Added non-variant children to variant_type output, and included
  DW_AT_discr_value attributes for variants. (Patch 9)

- Added another symbol pointer test case. (Patch 16)

- Picked up (Acked|Reviewed)-by tags from v3.

v3: https://lore.kernel.org/lkml/20240923181846.549877-22-samitolvanen@google.com/
- Updated SPX license headers.

- Squashed the first two patches in v2 and tried to reduce churn as
  much as reasonable.

- Dropped patch 18 from v2 ("x86/asm-prototypes: Include
  <asm/ptrace.h>") as it's addressed by a separate patch.

- Changed the error handling code to immediately terminate instead
  of propagating the errors back to main, which cleaned up the code
  quite a bit.

- Switched to the list and hashtable implementations in scripts and
  dropped the remaining tools/include dependencies. Added a couple
  missing list macros. (patch 1)

- Moved the genksyms CRC32 implementation to scripts/include and
  dropped the duplicate code. (patches 2 and 14)

- Switched from ad-hoc command line parsing to getopt_long (patch 3).

- Added structure member and function parameter names to the DIE
  output to match genksyms behavior, and tweaked the symtypes format
  to be more parser-friendly in general based on Petr's suggestions.

- Replaced the declaration-only struct annotations with more generic
  kABI stability rules that allow source code annotations to be used
  where #ifndef __GENKSYMS__ was previously used.  Added support for
  rules that can be used to exclude enumerators from versioning.
  (patch 16)

- Per Miroslav's suggestion, added an option to hide structure
  members from versioning when they're added to existing alignment
  holes, for example. (patch 16)

- Per Greg's request, added documentation and example macros for the
  --stable features, and a couple of test cases. (patches 15, 16, and
  20)

- Fixed making symtypes files, which need to depend on .o files with
  gendwarfksyms. (patch 19)

- Addressed several other smaller issues that Petr and Masahiro
  kindly pointed out during the v2 review.

v2: https://lore.kernel.org/lkml/20240815173903.4172139-21-samitolvanen@google.com/
- Per Luis' request, dropped Rust-specific patches and added
  gendwarfksyms as an alternative to genksyms for the entire
  kernel.

- Added support for missing DWARF features needed to handle
  also non-Rust code.

- Changed symbol address matching to use the symbol table
  information instead of relying on addresses in DWARF.

- Added __gendwarfksyms_ptr patches to ensure the compiler emits
  the necessary type information in DWARF even for symbols that
  are defined in other TUs.

- Refactored debugging output and moved the more verbose output
  behind --dump* flags.

- Added a --symtypes flag for generating a genksyms-style
  symtypes output based on Petr's feedback, and refactored
  symbol version calculations to be based on symtypes instead
  of raw --dump-dies output.

- Based on feedback from Greg and Petr, added --stable flag and
  support for reserved data structure fields and declaration-onl
  structures. Also added examples for using these features.

- Added a GENDWARFKSYMS option and hooked up kbuild support
  for both C and assembly code. Note that with gendwarfksyms,
  we have to actually build a temporary .o file for calculating
  assembly modversions.

v1: https://lore.kernel.org/lkml/20240617175818.58219-17-samitolvanen@google.com/

---

Sami Tolvanen (18):
  tools: Add gendwarfksyms
  gendwarfksyms: Add address matching
  gendwarfksyms: Expand base_type
  gendwarfksyms: Add a cache for processed DIEs
  gendwarfksyms: Expand type modifiers and typedefs
  gendwarfksyms: Expand subroutine_type
  gendwarfksyms: Expand array_type
  gendwarfksyms: Expand structure types
  gendwarfksyms: Limit structure expansion
  gendwarfksyms: Add die_map debugging
  gendwarfksyms: Add symtypes output
  gendwarfksyms: Add symbol versioning
  gendwarfksyms: Add support for kABI rules
  gendwarfksyms: Add support for reserved and ignored fields
  gendwarfksyms: Add support for symbol type pointers
  export: Add __gendwarfksyms_ptr_ references to exported symbols
  kbuild: Add gendwarfksyms as an alternative to genksyms
  Documentation/kbuild: Add DWARF module versioning

 Documentation/kbuild/gendwarfksyms.rst     |  308 ++++++
 Documentation/kbuild/index.rst             |    1 +
 MAINTAINERS                                |    7 +
 include/linux/export.h                     |   15 +
 kernel/module/Kconfig                      |   30 +
 scripts/Makefile                           |    3 +-
 scripts/Makefile.build                     |   35 +-
 scripts/gendwarfksyms/.gitignore           |    2 +
 scripts/gendwarfksyms/Makefile             |   12 +
 scripts/gendwarfksyms/cache.c              |   51 +
 scripts/gendwarfksyms/die.c                |  166 +++
 scripts/gendwarfksyms/dwarf.c              | 1159 ++++++++++++++++++++
 scripts/gendwarfksyms/examples/kabi.h      |  157 +++
 scripts/gendwarfksyms/examples/kabi_ex.c   |   30 +
 scripts/gendwarfksyms/examples/kabi_ex.h   |  263 +++++
 scripts/gendwarfksyms/examples/symbolptr.c |   33 +
 scripts/gendwarfksyms/gendwarfksyms.c      |  185 ++++
 scripts/gendwarfksyms/gendwarfksyms.h      |  296 +++++
 scripts/gendwarfksyms/kabi.c               |  336 ++++++
 scripts/gendwarfksyms/symbols.c            |  341 ++++++
 scripts/gendwarfksyms/types.c              |  481 ++++++++
 21 files changed, 3904 insertions(+), 7 deletions(-)
 create mode 100644 Documentation/kbuild/gendwarfksyms.rst
 create mode 100644 scripts/gendwarfksyms/.gitignore
 create mode 100644 scripts/gendwarfksyms/Makefile
 create mode 100644 scripts/gendwarfksyms/cache.c
 create mode 100644 scripts/gendwarfksyms/die.c
 create mode 100644 scripts/gendwarfksyms/dwarf.c
 create mode 100644 scripts/gendwarfksyms/examples/kabi.h
 create mode 100644 scripts/gendwarfksyms/examples/kabi_ex.c
 create mode 100644 scripts/gendwarfksyms/examples/kabi_ex.h
 create mode 100644 scripts/gendwarfksyms/examples/symbolptr.c
 create mode 100644 scripts/gendwarfksyms/gendwarfksyms.c
 create mode 100644 scripts/gendwarfksyms/gendwarfksyms.h
 create mode 100644 scripts/gendwarfksyms/kabi.c
 create mode 100644 scripts/gendwarfksyms/symbols.c
 create mode 100644 scripts/gendwarfksyms/types.c


base-commit: 78d4f34e2115b517bcbfe7ec0d018bbbb6f9b0b8
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 01/18] tools: Add gendwarfksyms

[Sami Tolvanen]

Add a basic DWARF parser, which uses libdw to traverse the debugging
information in an object file and looks for functions and variables.
In follow-up patches, this will be expanded to produce symbol versions
for CONFIG_MODVERSIONS from DWARF.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 MAINTAINERS                           |   7 ++
 kernel/module/Kconfig                 |   8 ++
 scripts/Makefile                      |   1 +
 scripts/gendwarfksyms/.gitignore      |   2 +
 scripts/gendwarfksyms/Makefile        |   8 ++
 scripts/gendwarfksyms/dwarf.c         | 166 ++++++++++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.c | 126 +++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.h |  95 +++++++++++++++
 scripts/gendwarfksyms/symbols.c       |  96 +++++++++++++++
 9 files changed, 509 insertions(+)
 create mode 100644 scripts/gendwarfksyms/.gitignore
 create mode 100644 scripts/gendwarfksyms/Makefile
 create mode 100644 scripts/gendwarfksyms/dwarf.c
 create mode 100644 scripts/gendwarfksyms/gendwarfksyms.c
 create mode 100644 scripts/gendwarfksyms/gendwarfksyms.h
 create mode 100644 scripts/gendwarfksyms/symbols.c

diff --git a/MAINTAINERS b/MAINTAINERS
index baf0eeb9a355..35bb18834b39 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -9550,6 +9550,13 @@ W:	https://linuxtv.org
 T:	git git://linuxtv.org/media.git
 F:	drivers/media/radio/radio-gemtek*
 
+GENDWARFKSYMS
+M:	Sami Tolvanen <samitolvanen@google.com>
+L:	linux-modules@vger.kernel.org
+L:	linux-kbuild@vger.kernel.org
+S:	Maintained
+F:	scripts/gendwarfksyms/
+
 GENERIC ARCHITECTURE TOPOLOGY
 M:	Sudeep Holla <sudeep.holla@arm.com>
 L:	linux-kernel@vger.kernel.org
diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 7b329057997a..4637f063d0fc 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -169,6 +169,14 @@ config MODVERSIONS
 	  make them incompatible with the kernel you are running.  If
 	  unsure, say N.
 
+config GENDWARFKSYMS
+	bool "gendwarfksyms (from debugging information)"
+	depends on DEBUG_INFO
+	# Requires full debugging information, split DWARF not supported.
+	depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT
+	# Requires ELF object files.
+	depends on !LTO
+
 config ASM_MODVERSIONS
 	bool
 	default HAVE_ASM_MODVERSIONS && MODVERSIONS
diff --git a/scripts/Makefile b/scripts/Makefile
index 6bcda4b9d054..d7fec46d38c0 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -54,6 +54,7 @@ targets += module.lds
 
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
 subdir-$(CONFIG_MODVERSIONS) += genksyms
+subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_SECURITY_IPE) += ipe
 
diff --git a/scripts/gendwarfksyms/.gitignore b/scripts/gendwarfksyms/.gitignore
new file mode 100644
index 000000000000..0927f8d3cd96
--- /dev/null
+++ b/scripts/gendwarfksyms/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+/gendwarfksyms
diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
new file mode 100644
index 000000000000..9f8fec4fd39b
--- /dev/null
+++ b/scripts/gendwarfksyms/Makefile
@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0
+hostprogs-always-y += gendwarfksyms
+
+gendwarfksyms-objs += gendwarfksyms.o
+gendwarfksyms-objs += dwarf.o
+gendwarfksyms-objs += symbols.o
+
+HOSTLDLIBS_gendwarfksyms := -ldw -lelf
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
new file mode 100644
index 000000000000..81df3e2ad3ae
--- /dev/null
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -0,0 +1,166 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+static bool get_ref_die_attr(Dwarf_Die *die, unsigned int id, Dwarf_Die *value)
+{
+	Dwarf_Attribute da;
+
+	/* dwarf_formref_die returns a pointer instead of an error value. */
+	return dwarf_attr(die, id, &da) && dwarf_formref_die(&da, value);
+}
+
+#define DEFINE_GET_STRING_ATTR(attr)                         \
+	static const char *get_##attr##_attr(Dwarf_Die *die) \
+	{                                                    \
+		Dwarf_Attribute da;                          \
+		if (dwarf_attr(die, DW_AT_##attr, &da))      \
+			return dwarf_formstring(&da);        \
+		return NULL;                                 \
+	}
+
+DEFINE_GET_STRING_ATTR(name)
+DEFINE_GET_STRING_ATTR(linkage_name)
+
+static const char *get_symbol_name(Dwarf_Die *die)
+{
+	const char *name;
+
+	/* rustc uses DW_AT_linkage_name for exported symbols */
+	name = get_linkage_name_attr(die);
+	if (!name)
+		name = get_name_attr(die);
+
+	return name;
+}
+
+static bool match_export_symbol(struct state *state, Dwarf_Die *die)
+{
+	Dwarf_Die *source = die;
+	Dwarf_Die origin;
+
+	/* If the DIE has an abstract origin, use it for type information. */
+	if (get_ref_die_attr(die, DW_AT_abstract_origin, &origin))
+		source = &origin;
+
+	state->sym = symbol_get(get_symbol_name(die));
+
+	/* Look up using the origin name if there are no matches. */
+	if (!state->sym && source != die)
+		state->sym = symbol_get(get_symbol_name(source));
+
+	state->die = *source;
+	return !!state->sym;
+}
+
+/*
+ * Type string processing
+ */
+static void process(const char *s)
+{
+	s = s ?: "<null>";
+
+	if (dump_dies)
+		fputs(s, stderr);
+}
+
+bool match_all(Dwarf_Die *die)
+{
+	return true;
+}
+
+int process_die_container(struct state *state, Dwarf_Die *die,
+			  die_callback_t func, die_match_callback_t match)
+{
+	Dwarf_Die current;
+	int res;
+
+	res = checkp(dwarf_child(die, &current));
+	while (!res) {
+		if (match(&current)) {
+			/* <0 = error, 0 = continue, >0 = stop */
+			res = checkp(func(state, &current));
+			if (res)
+				return res;
+		}
+
+		res = checkp(dwarf_siblingof(&current, &current));
+	}
+
+	return 0;
+}
+
+/*
+ * Exported symbol processing
+ */
+static void process_symbol(struct state *state, Dwarf_Die *die,
+			   die_callback_t process_func)
+{
+	debug("%s", state->sym->name);
+	check(process_func(state, die));
+	if (dump_dies)
+		fputs("\n", stderr);
+}
+
+static int __process_subprogram(struct state *state, Dwarf_Die *die)
+{
+	process("subprogram");
+	return 0;
+}
+
+static void process_subprogram(struct state *state, Dwarf_Die *die)
+{
+	process_symbol(state, die, __process_subprogram);
+}
+
+static int __process_variable(struct state *state, Dwarf_Die *die)
+{
+	process("variable ");
+	return 0;
+}
+
+static void process_variable(struct state *state, Dwarf_Die *die)
+{
+	process_symbol(state, die, __process_variable);
+}
+
+static int process_exported_symbols(struct state *unused, Dwarf_Die *die)
+{
+	int tag = dwarf_tag(die);
+
+	switch (tag) {
+	/* Possible containers of exported symbols */
+	case DW_TAG_namespace:
+	case DW_TAG_class_type:
+	case DW_TAG_structure_type:
+		return check(process_die_container(
+			NULL, die, process_exported_symbols, match_all));
+
+	/* Possible exported symbols */
+	case DW_TAG_subprogram:
+	case DW_TAG_variable: {
+		struct state state;
+
+		if (!match_export_symbol(&state, die))
+			return 0;
+
+		if (tag == DW_TAG_subprogram)
+			process_subprogram(&state, &state.die);
+		else
+			process_variable(&state, &state.die);
+
+		return 0;
+	}
+	default:
+		return 0;
+	}
+}
+
+void process_cu(Dwarf_Die *cudie)
+{
+	check(process_die_container(NULL, cudie, process_exported_symbols,
+				    match_all));
+}
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
new file mode 100644
index 000000000000..f84fa98fcbdb
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <fcntl.h>
+#include <getopt.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <string.h>
+#include <unistd.h>
+#include "gendwarfksyms.h"
+
+/*
+ * Options
+ */
+
+/* Print debugging information to stderr */
+int debug;
+/* Dump DIE contents */
+int dump_dies;
+
+static void usage(void)
+{
+	fputs("Usage: gendwarfksyms [options] elf-object-file ... < symbol-list\n\n"
+	      "Options:\n"
+	      "  -d, --debug          Print debugging information\n"
+	      "      --dump-dies      Dump DWARF DIE contents\n"
+	      "  -h, --help           Print this message\n"
+	      "\n",
+	      stderr);
+}
+
+static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
+			  Dwarf_Addr base, void *arg)
+{
+	Dwarf_Addr dwbias;
+	Dwarf_Die cudie;
+	Dwarf_CU *cu = NULL;
+	Dwarf *dbg;
+	int res;
+
+	debug("%s", name);
+	dbg = dwfl_module_getdwarf(mod, &dwbias);
+
+	do {
+		res = dwarf_get_units(dbg, cu, &cu, NULL, NULL, &cudie, NULL);
+		if (res < 0)
+			error("dwarf_get_units failed: no debugging information?");
+		if (res == 1)
+			break; /* No more units */
+
+		process_cu(&cudie);
+	} while (cu);
+
+	return DWARF_CB_OK;
+}
+
+static const Dwfl_Callbacks callbacks = {
+	.section_address = dwfl_offline_section_address,
+	.find_debuginfo = dwfl_standard_find_debuginfo,
+};
+
+int main(int argc, char **argv)
+{
+	unsigned int n;
+	int opt;
+
+	struct option opts[] = { { "debug", 0, NULL, 'd' },
+				 { "dump-dies", 0, &dump_dies, 1 },
+				 { "help", 0, NULL, 'h' },
+				 { 0, 0, NULL, 0 } };
+
+	while ((opt = getopt_long(argc, argv, "dh", opts, NULL)) != EOF) {
+		switch (opt) {
+		case 0:
+			break;
+		case 'd':
+			debug = 1;
+			break;
+		case 'h':
+			usage();
+			return 0;
+		default:
+			usage();
+			return 1;
+		}
+	}
+
+	if (optind >= argc) {
+		usage();
+		error("no input files?");
+	}
+
+	symbol_read_exports(stdin);
+
+	for (n = optind; n < argc; n++) {
+		Dwfl *dwfl;
+		int fd;
+
+		fd = open(argv[n], O_RDONLY);
+		if (fd == -1)
+			error("open failed for '%s': %s", argv[n],
+			      strerror(errno));
+
+		dwfl = dwfl_begin(&callbacks);
+		if (!dwfl)
+			error("dwfl_begin failed for '%s': %s", argv[n],
+			      dwarf_errmsg(-1));
+
+		if (!dwfl_report_offline(dwfl, argv[n], argv[n], fd))
+			error("dwfl_report_offline failed for '%s': %s",
+			      argv[n], dwarf_errmsg(-1));
+
+		dwfl_report_end(dwfl, NULL, NULL);
+
+		if (dwfl_getmodules(dwfl, &process_module, NULL, 0))
+			error("dwfl_getmodules failed for '%s'", argv[n]);
+
+		dwfl_end(dwfl);
+	}
+
+	symbol_free();
+
+	return 0;
+}
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
new file mode 100644
index 000000000000..5c8288c71fdd
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <dwarf.h>
+#include <elfutils/libdw.h>
+#include <elfutils/libdwfl.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <hash.h>
+#include <hashtable.h>
+#include <xalloc.h>
+
+#ifndef __GENDWARFKSYMS_H
+#define __GENDWARFKSYMS_H
+
+/*
+ * Options -- in gendwarfksyms.c
+ */
+extern int debug;
+extern int dump_dies;
+
+/*
+ * Output helpers
+ */
+#define __PREFIX "gendwarfksyms: "
+#define __println(prefix, format, ...)                                \
+	fprintf(stderr, prefix __PREFIX "%s: " format "\n", __func__, \
+		##__VA_ARGS__)
+
+#define debug(format, ...)                                    \
+	do {                                                  \
+		if (debug)                                    \
+			__println("", format, ##__VA_ARGS__); \
+	} while (0)
+
+#define warn(format, ...) __println("warning: ", format, ##__VA_ARGS__)
+#define error(format, ...)                                   \
+	do {                                                 \
+		__println("error: ", format, ##__VA_ARGS__); \
+		exit(1);                                     \
+	} while (0)
+
+/*
+ * Error handling helpers
+ */
+#define __check(expr, test)                                     \
+	({                                                      \
+		int __res = expr;                               \
+		if (test)                                       \
+			error("`%s` failed: %d", #expr, __res); \
+		__res;                                          \
+	})
+
+/* Error == non-zero values */
+#define check(expr) __check(expr, __res)
+/* Error == negative values */
+#define checkp(expr) __check(expr, __res < 0)
+
+/*
+ * symbols.c
+ */
+
+struct symbol {
+	const char *name;
+	struct hlist_node name_hash;
+};
+
+typedef void (*symbol_callback_t)(struct symbol *, void *arg);
+
+void symbol_read_exports(FILE *file);
+struct symbol *symbol_get(const char *name);
+void symbol_free(void);
+
+/*
+ * dwarf.c
+ */
+
+struct state {
+	struct symbol *sym;
+	Dwarf_Die die;
+};
+
+typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
+typedef bool (*die_match_callback_t)(Dwarf_Die *die);
+bool match_all(Dwarf_Die *die);
+
+int process_die_container(struct state *state, Dwarf_Die *die,
+			  die_callback_t func, die_match_callback_t match);
+
+void process_cu(Dwarf_Die *cudie);
+
+#endif /* __GENDWARFKSYMS_H */
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
new file mode 100644
index 000000000000..7adf2ed9b89b
--- /dev/null
+++ b/scripts/gendwarfksyms/symbols.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+#define SYMBOL_HASH_BITS 12
+static HASHTABLE_DEFINE(symbol_names, 1 << SYMBOL_HASH_BITS);
+
+static unsigned int for_each(const char *name, symbol_callback_t func,
+			     void *data)
+{
+	struct hlist_node *tmp;
+	struct symbol *match;
+
+	if (!name || !*name)
+		return 0;
+
+	hash_for_each_possible_safe(symbol_names, match, tmp, name_hash,
+				    hash_str(name)) {
+		if (strcmp(match->name, name))
+			continue;
+
+		if (func)
+			func(match, data);
+
+		return 1;
+	}
+
+	return 0;
+}
+
+static bool is_exported(const char *name)
+{
+	return for_each(name, NULL, NULL) > 0;
+}
+
+void symbol_read_exports(FILE *file)
+{
+	struct symbol *sym;
+	char *line = NULL;
+	char *name = NULL;
+	size_t size = 0;
+	int nsym = 0;
+
+	while (getline(&line, &size, file) > 0) {
+		if (sscanf(line, "%ms\n", &name) != 1)
+			error("malformed input line: %s", line);
+
+		if (is_exported(name)) {
+			/* Ignore duplicates */
+			free(name);
+			continue;
+		}
+
+		sym = xcalloc(1, sizeof(struct symbol));
+		sym->name = name;
+
+		hash_add(symbol_names, &sym->name_hash, hash_str(sym->name));
+		++nsym;
+
+		debug("%s", sym->name);
+	}
+
+	free(line);
+	debug("%d exported symbols", nsym);
+}
+
+static void get_symbol(struct symbol *sym, void *arg)
+{
+	struct symbol **res = arg;
+
+	*res = sym;
+}
+
+struct symbol *symbol_get(const char *name)
+{
+	struct symbol *sym = NULL;
+
+	for_each(name, get_symbol, &sym);
+	return sym;
+}
+
+void symbol_free(void)
+{
+	struct hlist_node *tmp;
+	struct symbol *sym;
+
+	hash_for_each_safe(symbol_names, sym, tmp, name_hash) {
+		free((void *)sym->name);
+		free(sym);
+	}
+
+	hash_init(symbol_names);
+}
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 02/18] gendwarfksyms: Add address matching

[Sami Tolvanen]

The compiler may choose not to emit type information in DWARF for all
aliases, but it's possible for each alias to be exported separately.
To ensure we find type information for the aliases as well, read
{section, address} tuples from the symbol table and match symbols also
by address.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/gendwarfksyms.c |   2 +
 scripts/gendwarfksyms/gendwarfksyms.h |  13 ++
 scripts/gendwarfksyms/symbols.c       | 163 ++++++++++++++++++++++++++
 3 files changed, 178 insertions(+)

diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index f84fa98fcbdb..1763234b6329 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -103,6 +103,8 @@ int main(int argc, char **argv)
 			error("open failed for '%s': %s", argv[n],
 			      strerror(errno));
 
+		symbol_read_symtab(fd);
+
 		dwfl = dwfl_begin(&callbacks);
 		if (!dwfl)
 			error("dwfl_begin failed for '%s': %s", argv[n],
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 5c8288c71fdd..cb9fd78a58da 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -63,14 +63,27 @@ extern int dump_dies;
  * symbols.c
  */
 
+static inline unsigned int addr_hash(uintptr_t addr)
+{
+	return hash_ptr((const void *)addr);
+}
+
+struct symbol_addr {
+	uint32_t section;
+	Elf64_Addr address;
+};
+
 struct symbol {
 	const char *name;
+	struct symbol_addr addr;
+	struct hlist_node addr_hash;
 	struct hlist_node name_hash;
 };
 
 typedef void (*symbol_callback_t)(struct symbol *, void *arg);
 
 void symbol_read_exports(FILE *file);
+void symbol_read_symtab(int fd);
 struct symbol *symbol_get(const char *name);
 void symbol_free(void);
 
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
index 7adf2ed9b89b..98febb524dd5 100644
--- a/scripts/gendwarfksyms/symbols.c
+++ b/scripts/gendwarfksyms/symbols.c
@@ -6,8 +6,39 @@
 #include "gendwarfksyms.h"
 
 #define SYMBOL_HASH_BITS 12
+
+/* struct symbol_addr -> struct symbol */
+static HASHTABLE_DEFINE(symbol_addrs, 1 << SYMBOL_HASH_BITS);
+/* name -> struct symbol */
 static HASHTABLE_DEFINE(symbol_names, 1 << SYMBOL_HASH_BITS);
 
+static inline unsigned int symbol_addr_hash(const struct symbol_addr *addr)
+{
+	return hash_32(addr->section ^ addr_hash(addr->address));
+}
+
+static unsigned int __for_each_addr(struct symbol *sym, symbol_callback_t func,
+				    void *data)
+{
+	struct hlist_node *tmp;
+	struct symbol *match = NULL;
+	unsigned int processed = 0;
+
+	hash_for_each_possible_safe(symbol_addrs, match, tmp, addr_hash,
+				    symbol_addr_hash(&sym->addr)) {
+		if (match == sym)
+			continue; /* Already processed */
+
+		if (match->addr.section == sym->addr.section &&
+		    match->addr.address == sym->addr.address) {
+			func(match, data);
+			++processed;
+		}
+	}
+
+	return processed;
+}
+
 static unsigned int for_each(const char *name, symbol_callback_t func,
 			     void *data)
 {
@@ -22,9 +53,13 @@ static unsigned int for_each(const char *name, symbol_callback_t func,
 		if (strcmp(match->name, name))
 			continue;
 
+		/* Call func for the match, and all address matches */
 		if (func)
 			func(match, data);
 
+		if (match->addr.section != SHN_UNDEF)
+			return __for_each_addr(match, func, data) + 1;
+
 		return 1;
 	}
 
@@ -56,6 +91,7 @@ void symbol_read_exports(FILE *file)
 
 		sym = xcalloc(1, sizeof(struct symbol));
 		sym->name = name;
+		sym->addr.section = SHN_UNDEF;
 
 		hash_add(symbol_names, &sym->name_hash, hash_str(sym->name));
 		++nsym;
@@ -82,6 +118,132 @@ struct symbol *symbol_get(const char *name)
 	return sym;
 }
 
+typedef void (*elf_symbol_callback_t)(const char *name, GElf_Sym *sym,
+				      Elf32_Word xndx, void *arg);
+
+static void elf_for_each_global(int fd, elf_symbol_callback_t func, void *arg)
+{
+	size_t sym_size;
+	GElf_Shdr shdr_mem;
+	GElf_Shdr *shdr;
+	Elf_Data *xndx_data = NULL;
+	Elf_Scn *scn;
+	Elf *elf;
+
+	if (elf_version(EV_CURRENT) != EV_CURRENT)
+		error("elf_version failed: %s", elf_errmsg(-1));
+
+	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+	if (!elf)
+		error("elf_begin failed: %s", elf_errmsg(-1));
+
+	scn = elf_nextscn(elf, NULL);
+
+	while (scn) {
+		shdr = gelf_getshdr(scn, &shdr_mem);
+		if (!shdr)
+			error("gelf_getshdr failed: %s", elf_errmsg(-1));
+
+		if (shdr->sh_type == SHT_SYMTAB_SHNDX) {
+			xndx_data = elf_getdata(scn, NULL);
+			if (!xndx_data)
+				error("elf_getdata failed: %s", elf_errmsg(-1));
+			break;
+		}
+
+		scn = elf_nextscn(elf, scn);
+	}
+
+	sym_size = gelf_fsize(elf, ELF_T_SYM, 1, EV_CURRENT);
+	scn = elf_nextscn(elf, NULL);
+
+	while (scn) {
+		shdr = gelf_getshdr(scn, &shdr_mem);
+		if (!shdr)
+			error("gelf_getshdr failed: %s", elf_errmsg(-1));
+
+		if (shdr->sh_type == SHT_SYMTAB) {
+			unsigned int nsyms;
+			unsigned int n;
+			Elf_Data *data = elf_getdata(scn, NULL);
+
+			if (!data)
+				error("elf_getdata failed: %s", elf_errmsg(-1));
+
+			if (shdr->sh_entsize != sym_size)
+				error("expected sh_entsize (%lu) to be %zu",
+				      shdr->sh_entsize, sym_size);
+
+			nsyms = shdr->sh_size / shdr->sh_entsize;
+
+			for (n = 1; n < nsyms; ++n) {
+				const char *name = NULL;
+				Elf32_Word xndx = 0;
+				GElf_Sym sym_mem;
+				GElf_Sym *sym;
+
+				sym = gelf_getsymshndx(data, xndx_data, n,
+						       &sym_mem, &xndx);
+				if (!sym)
+					error("gelf_getsymshndx failed: %s",
+					      elf_errmsg(-1));
+
+				if (GELF_ST_BIND(sym->st_info) == STB_LOCAL)
+					continue;
+
+				if (sym->st_shndx != SHN_XINDEX)
+					xndx = sym->st_shndx;
+
+				name = elf_strptr(elf, shdr->sh_link,
+						  sym->st_name);
+				if (!name)
+					error("elf_strptr failed: %s",
+					      elf_errmsg(-1));
+
+				/* Skip empty symbol names */
+				if (*name)
+					func(name, sym, xndx, arg);
+			}
+		}
+
+		scn = elf_nextscn(elf, scn);
+	}
+
+	check(elf_end(elf));
+}
+
+static void set_symbol_addr(struct symbol *sym, void *arg)
+{
+	struct symbol_addr *addr = arg;
+
+	if (sym->addr.section == SHN_UNDEF) {
+		sym->addr = *addr;
+		hash_add(symbol_addrs, &sym->addr_hash,
+			 symbol_addr_hash(&sym->addr));
+
+		debug("%s -> { %u, %lx }", sym->name, sym->addr.section,
+		      sym->addr.address);
+	} else if (sym->addr.section != addr->section ||
+		   sym->addr.address != addr->address) {
+		warn("multiple addresses for symbol %s?", sym->name);
+	}
+}
+
+static void elf_set_symbol_addr(const char *name, GElf_Sym *sym,
+				Elf32_Word xndx, void *arg)
+{
+	struct symbol_addr addr = { .section = xndx, .address = sym->st_value };
+
+	/* Set addresses for exported symbols */
+	if (addr.section != SHN_UNDEF)
+		for_each(name, set_symbol_addr, &addr);
+}
+
+void symbol_read_symtab(int fd)
+{
+	elf_for_each_global(fd, elf_set_symbol_addr, NULL);
+}
+
 void symbol_free(void)
 {
 	struct hlist_node *tmp;
@@ -92,5 +254,6 @@ void symbol_free(void)
 		free(sym);
 	}
 
+	hash_init(symbol_addrs);
 	hash_init(symbol_names);
 }
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 03/18] gendwarfksyms: Expand base_type

[Sami Tolvanen]

Start making gendwarfksyms more useful by adding support for
expanding DW_TAG_base_type types and basic DWARF attributes.

Example:

  $ echo loops_per_jiffy | \
      scripts/gendwarfksyms/gendwarfksyms \
        --debug --dump-dies vmlinux.o
  ...
  gendwarfksyms: process_symbol: loops_per_jiffy
  variable base_type unsigned long byte_size(8) encoding(7)
  ...

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c | 160 ++++++++++++++++++++++++++++++++++
 1 file changed, 160 insertions(+)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 81df3e2ad3ae..74e75b8ec891 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -3,8 +3,21 @@
  * Copyright (C) 2024 Google LLC
  */
 
+#include <inttypes.h>
+#include <stdarg.h>
 #include "gendwarfksyms.h"
 
+#define DEFINE_GET_ATTR(attr, type)                                    \
+	static bool get_##attr##_attr(Dwarf_Die *die, unsigned int id, \
+				      type *value)                     \
+	{                                                              \
+		Dwarf_Attribute da;                                    \
+		return dwarf_attr(die, id, &da) &&                     \
+		       !dwarf_form##attr(&da, value);                  \
+	}
+
+DEFINE_GET_ATTR(udata, Dwarf_Word)
+
 static bool get_ref_die_attr(Dwarf_Die *die, unsigned int id, Dwarf_Die *value)
 {
 	Dwarf_Attribute da;
@@ -67,6 +80,109 @@ static void process(const char *s)
 		fputs(s, stderr);
 }
 
+#define MAX_FMT_BUFFER_SIZE 128
+
+static void process_fmt(const char *fmt, ...)
+{
+	char buf[MAX_FMT_BUFFER_SIZE];
+	va_list args;
+
+	va_start(args, fmt);
+
+	if (checkp(vsnprintf(buf, sizeof(buf), fmt, args)) >= sizeof(buf))
+		error("vsnprintf overflow: increase MAX_FMT_BUFFER_SIZE");
+
+	process(buf);
+	va_end(args);
+}
+
+#define MAX_FQN_SIZE 64
+
+/* Get a fully qualified name from DWARF scopes */
+static char *get_fqn(Dwarf_Die *die)
+{
+	const char *list[MAX_FQN_SIZE];
+	Dwarf_Die *scopes = NULL;
+	bool has_name = false;
+	char *fqn = NULL;
+	char *p;
+	int count = 0;
+	int len = 0;
+	int res;
+	int i;
+
+	res = checkp(dwarf_getscopes_die(die, &scopes));
+	if (!res) {
+		list[count] = get_name_attr(die);
+
+		if (!list[count])
+			return NULL;
+
+		len += strlen(list[count]);
+		count++;
+
+		goto done;
+	}
+
+	for (i = res - 1; i >= 0 && count < MAX_FQN_SIZE; i--) {
+		if (dwarf_tag(&scopes[i]) == DW_TAG_compile_unit)
+			continue;
+
+		list[count] = get_name_attr(&scopes[i]);
+
+		if (list[count]) {
+			has_name = true;
+		} else {
+			list[count] = "<anonymous>";
+			has_name = false;
+		}
+
+		len += strlen(list[count]);
+		count++;
+
+		if (i > 0) {
+			list[count++] = "::";
+			len += 2;
+		}
+	}
+
+	free(scopes);
+
+	if (count == MAX_FQN_SIZE)
+		warn("increase MAX_FQN_SIZE: reached the maximum");
+
+	/* Consider the DIE unnamed if the last scope doesn't have a name */
+	if (!has_name)
+		return NULL;
+done:
+	fqn = xmalloc(len + 1);
+	*fqn = '\0';
+
+	p = fqn;
+	for (i = 0; i < count; i++)
+		p = stpcpy(p, list[i]);
+
+	return fqn;
+}
+
+static void process_fqn(Dwarf_Die *die)
+{
+	process(" ");
+	process(get_fqn(die) ?: "");
+}
+
+#define DEFINE_PROCESS_UDATA_ATTRIBUTE(attribute)                           \
+	static void process_##attribute##_attr(Dwarf_Die *die)              \
+	{                                                                   \
+		Dwarf_Word value;                                           \
+		if (get_udata_attr(die, DW_AT_##attribute, &value))         \
+			process_fmt(" " #attribute "(%" PRIu64 ")", value); \
+	}
+
+DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
+
 bool match_all(Dwarf_Die *die)
 {
 	return true;
@@ -93,6 +209,49 @@ int process_die_container(struct state *state, Dwarf_Die *die,
 	return 0;
 }
 
+static int process_type(struct state *state, Dwarf_Die *die);
+
+static void process_type_attr(struct state *state, Dwarf_Die *die)
+{
+	Dwarf_Die type;
+
+	if (get_ref_die_attr(die, DW_AT_type, &type)) {
+		check(process_type(state, &type));
+		return;
+	}
+
+	/* Compilers can omit DW_AT_type -- print out 'void' to clarify */
+	process("base_type void");
+}
+
+static void process_base_type(struct state *state, Dwarf_Die *die)
+{
+	process("base_type");
+	process_fqn(die);
+	process_byte_size_attr(die);
+	process_encoding_attr(die);
+	process_alignment_attr(die);
+}
+
+#define PROCESS_TYPE(type)                         \
+	case DW_TAG_##type##_type:                 \
+		process_##type##_type(state, die); \
+		break;
+
+static int process_type(struct state *state, Dwarf_Die *die)
+{
+	int tag = dwarf_tag(die);
+
+	switch (tag) {
+	PROCESS_TYPE(base)
+	default:
+		debug("unimplemented type: %x", tag);
+		break;
+	}
+
+	return 0;
+}
+
 /*
  * Exported symbol processing
  */
@@ -119,6 +278,7 @@ static void process_subprogram(struct state *state, Dwarf_Die *die)
 static int __process_variable(struct state *state, Dwarf_Die *die)
 {
 	process("variable ");
+	process_type_attr(state, die);
 	return 0;
 }
 
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 04/18] gendwarfksyms: Add a cache for processed DIEs

[Sami Tolvanen]

Basic types in DWARF repeat frequently and traversing the DIEs using
libdw is relatively slow. Add a simple hashtable based cache for the
processed DIEs.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/Makefile        |   1 +
 scripts/gendwarfksyms/die.c           | 143 ++++++++++++++++++++++++++
 scripts/gendwarfksyms/dwarf.c         | 136 +++++++++++++++++-------
 scripts/gendwarfksyms/gendwarfksyms.c |   6 ++
 scripts/gendwarfksyms/gendwarfksyms.h |  63 +++++++++++-
 5 files changed, 308 insertions(+), 41 deletions(-)
 create mode 100644 scripts/gendwarfksyms/die.c

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index 9f8fec4fd39b..c0d4ce50fc27 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -2,6 +2,7 @@
 hostprogs-always-y += gendwarfksyms
 
 gendwarfksyms-objs += gendwarfksyms.o
+gendwarfksyms-objs += die.o
 gendwarfksyms-objs += dwarf.o
 gendwarfksyms-objs += symbols.o
 
diff --git a/scripts/gendwarfksyms/die.c b/scripts/gendwarfksyms/die.c
new file mode 100644
index 000000000000..b7d900c6a9c8
--- /dev/null
+++ b/scripts/gendwarfksyms/die.c
@@ -0,0 +1,143 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <string.h>
+#include "gendwarfksyms.h"
+
+#define DIE_HASH_BITS 15
+
+/* {die->addr, state} -> struct die * */
+static HASHTABLE_DEFINE(die_map, 1 << DIE_HASH_BITS);
+
+static unsigned int map_hits;
+static unsigned int map_misses;
+
+static inline unsigned int die_hash(uintptr_t addr, enum die_state state)
+{
+	return hash_32(addr_hash(addr) ^ (unsigned int)state);
+}
+
+static void init_die(struct die *cd)
+{
+	cd->state = DIE_INCOMPLETE;
+	cd->fqn = NULL;
+	cd->tag = -1;
+	cd->addr = 0;
+	INIT_LIST_HEAD(&cd->fragments);
+}
+
+static struct die *create_die(Dwarf_Die *die, enum die_state state)
+{
+	struct die *cd;
+
+	cd = xmalloc(sizeof(struct die));
+	init_die(cd);
+	cd->addr = (uintptr_t)die->addr;
+
+	hash_add(die_map, &cd->hash, die_hash(cd->addr, state));
+	return cd;
+}
+
+int __die_map_get(uintptr_t addr, enum die_state state, struct die **res)
+{
+	struct die *cd;
+
+	hash_for_each_possible(die_map, cd, hash, die_hash(addr, state)) {
+		if (cd->addr == addr && cd->state == state) {
+			*res = cd;
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
+struct die *die_map_get(Dwarf_Die *die, enum die_state state)
+{
+	struct die *cd;
+
+	if (__die_map_get((uintptr_t)die->addr, state, &cd) == 0) {
+		map_hits++;
+		return cd;
+	}
+
+	map_misses++;
+	return create_die(die, state);
+}
+
+static void reset_die(struct die *cd)
+{
+	struct die_fragment *tmp;
+	struct die_fragment *df;
+
+	list_for_each_entry_safe(df, tmp, &cd->fragments, list) {
+		if (df->type == FRAGMENT_STRING)
+			free(df->data.str);
+		free(df);
+	}
+
+	if (cd->fqn && *cd->fqn)
+		free(cd->fqn);
+	init_die(cd);
+}
+
+void die_map_free(void)
+{
+	struct hlist_node *tmp;
+	unsigned int stats[DIE_LAST + 1];
+	struct die *cd;
+	int i;
+
+	memset(stats, 0, sizeof(stats));
+
+	hash_for_each_safe(die_map, cd, tmp, hash) {
+		stats[cd->state]++;
+		reset_die(cd);
+		free(cd);
+	}
+	hash_init(die_map);
+
+	if (map_hits + map_misses > 0)
+		debug("hits %u, misses %u (hit rate %.02f%%)", map_hits,
+		      map_misses,
+		      (100.0f * map_hits) / (map_hits + map_misses));
+
+	for (i = 0; i <= DIE_LAST; i++)
+		debug("%s: %u entries", die_state_name(i), stats[i]);
+}
+
+static struct die_fragment *append_item(struct die *cd)
+{
+	struct die_fragment *df;
+
+	df = xmalloc(sizeof(struct die_fragment));
+	df->type = FRAGMENT_EMPTY;
+	list_add_tail(&df->list, &cd->fragments);
+	return df;
+}
+
+void die_map_add_string(struct die *cd, const char *str)
+{
+	struct die_fragment *df;
+
+	if (!cd)
+		return;
+
+	df = append_item(cd);
+	df->data.str = xstrdup(str);
+	df->type = FRAGMENT_STRING;
+}
+
+void die_map_add_die(struct die *cd, struct die *child)
+{
+	struct die_fragment *df;
+
+	if (!cd)
+		return;
+
+	df = append_item(cd);
+	df->data.addr = child->addr;
+	df->type = FRAGMENT_DIE;
+}
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 74e75b8ec891..f40e23a547da 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -72,17 +72,19 @@ static bool match_export_symbol(struct state *state, Dwarf_Die *die)
 /*
  * Type string processing
  */
-static void process(const char *s)
+static void process(struct die *cache, const char *s)
 {
 	s = s ?: "<null>";
 
 	if (dump_dies)
 		fputs(s, stderr);
+
+	die_map_add_string(cache, s);
 }
 
 #define MAX_FMT_BUFFER_SIZE 128
 
-static void process_fmt(const char *fmt, ...)
+static void process_fmt(struct die *cache, const char *fmt, ...)
 {
 	char buf[MAX_FMT_BUFFER_SIZE];
 	va_list args;
@@ -92,7 +94,7 @@ static void process_fmt(const char *fmt, ...)
 	if (checkp(vsnprintf(buf, sizeof(buf), fmt, args)) >= sizeof(buf))
 		error("vsnprintf overflow: increase MAX_FMT_BUFFER_SIZE");
 
-	process(buf);
+	process(cache, buf);
 	va_end(args);
 }
 
@@ -165,18 +167,28 @@ static char *get_fqn(Dwarf_Die *die)
 	return fqn;
 }
 
-static void process_fqn(Dwarf_Die *die)
+static void update_fqn(struct die *cache, Dwarf_Die *die)
+{
+	if (!cache->fqn)
+		cache->fqn = get_fqn(die) ?: "";
+}
+
+static void process_fqn(struct die *cache, Dwarf_Die *die)
 {
-	process(" ");
-	process(get_fqn(die) ?: "");
+	update_fqn(cache, die);
+	if (*cache->fqn)
+		process(cache, " ");
+	process(cache, cache->fqn);
 }
 
-#define DEFINE_PROCESS_UDATA_ATTRIBUTE(attribute)                           \
-	static void process_##attribute##_attr(Dwarf_Die *die)              \
-	{                                                                   \
-		Dwarf_Word value;                                           \
-		if (get_udata_attr(die, DW_AT_##attribute, &value))         \
-			process_fmt(" " #attribute "(%" PRIu64 ")", value); \
+#define DEFINE_PROCESS_UDATA_ATTRIBUTE(attribute)                          \
+	static void process_##attribute##_attr(struct die *cache,          \
+					       Dwarf_Die *die)             \
+	{                                                                  \
+		Dwarf_Word value;                                          \
+		if (get_udata_attr(die, DW_AT_##attribute, &value))        \
+			process_fmt(cache, " " #attribute "(%" PRIu64 ")", \
+				    value);                                \
 	}
 
 DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
@@ -188,8 +200,9 @@ bool match_all(Dwarf_Die *die)
 	return true;
 }
 
-int process_die_container(struct state *state, Dwarf_Die *die,
-			  die_callback_t func, die_match_callback_t match)
+int process_die_container(struct state *state, struct die *cache,
+			  Dwarf_Die *die, die_callback_t func,
+			  die_match_callback_t match)
 {
 	Dwarf_Die current;
 	int res;
@@ -198,7 +211,7 @@ int process_die_container(struct state *state, Dwarf_Die *die,
 	while (!res) {
 		if (match(&current)) {
 			/* <0 = error, 0 = continue, >0 = stop */
-			res = checkp(func(state, &current));
+			res = checkp(func(state, cache, &current));
 			if (res)
 				return res;
 		}
@@ -209,39 +222,78 @@ int process_die_container(struct state *state, Dwarf_Die *die,
 	return 0;
 }
 
-static int process_type(struct state *state, Dwarf_Die *die);
+static int process_type(struct state *state, struct die *parent,
+			Dwarf_Die *die);
 
-static void process_type_attr(struct state *state, Dwarf_Die *die)
+static void process_type_attr(struct state *state, struct die *cache,
+			      Dwarf_Die *die)
 {
 	Dwarf_Die type;
 
 	if (get_ref_die_attr(die, DW_AT_type, &type)) {
-		check(process_type(state, &type));
+		check(process_type(state, cache, &type));
 		return;
 	}
 
 	/* Compilers can omit DW_AT_type -- print out 'void' to clarify */
-	process("base_type void");
+	process(cache, "base_type void");
+}
+
+static void process_base_type(struct state *state, struct die *cache,
+			      Dwarf_Die *die)
+{
+	process(cache, "base_type");
+	process_fqn(cache, die);
+	process_byte_size_attr(cache, die);
+	process_encoding_attr(cache, die);
+	process_alignment_attr(cache, die);
 }
 
-static void process_base_type(struct state *state, Dwarf_Die *die)
+static void process_cached(struct state *state, struct die *cache,
+			   Dwarf_Die *die)
 {
-	process("base_type");
-	process_fqn(die);
-	process_byte_size_attr(die);
-	process_encoding_attr(die);
-	process_alignment_attr(die);
+	struct die_fragment *df;
+	Dwarf_Die child;
+
+	list_for_each_entry(df, &cache->fragments, list) {
+		switch (df->type) {
+		case FRAGMENT_STRING:
+			process(NULL, df->data.str);
+			break;
+		case FRAGMENT_DIE:
+			if (!dwarf_die_addr_die(dwarf_cu_getdwarf(die->cu),
+						(void *)df->data.addr, &child))
+				error("dwarf_die_addr_die failed");
+			check(process_type(state, NULL, &child));
+			break;
+		default:
+			error("empty die_fragment");
+		}
+	}
 }
 
-#define PROCESS_TYPE(type)                         \
-	case DW_TAG_##type##_type:                 \
-		process_##type##_type(state, die); \
+#define PROCESS_TYPE(type)                                \
+	case DW_TAG_##type##_type:                        \
+		process_##type##_type(state, cache, die); \
 		break;
 
-static int process_type(struct state *state, Dwarf_Die *die)
+static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 {
+	struct die *cache;
 	int tag = dwarf_tag(die);
 
+	/*
+	 * If we have the DIE already cached, use it instead of walking
+	 * through DWARF.
+	 */
+	cache = die_map_get(die, DIE_COMPLETE);
+
+	if (cache->state == DIE_COMPLETE) {
+		process_cached(state, cache, die);
+		die_map_add_die(parent, cache);
+		return 0;
+	}
+
 	switch (tag) {
 	PROCESS_TYPE(base)
 	default:
@@ -249,6 +301,11 @@ static int process_type(struct state *state, Dwarf_Die *die)
 		break;
 	}
 
+	/* Update cache state and append to the parent (if any) */
+	cache->tag = tag;
+	cache->state = DIE_COMPLETE;
+	die_map_add_die(parent, cache);
+
 	return 0;
 }
 
@@ -259,14 +316,15 @@ static void process_symbol(struct state *state, Dwarf_Die *die,
 			   die_callback_t process_func)
 {
 	debug("%s", state->sym->name);
-	check(process_func(state, die));
+	check(process_func(state, NULL, die));
 	if (dump_dies)
 		fputs("\n", stderr);
 }
 
-static int __process_subprogram(struct state *state, Dwarf_Die *die)
+static int __process_subprogram(struct state *state, struct die *cache,
+				Dwarf_Die *die)
 {
-	process("subprogram");
+	process(cache, "subprogram");
 	return 0;
 }
 
@@ -275,10 +333,11 @@ static void process_subprogram(struct state *state, Dwarf_Die *die)
 	process_symbol(state, die, __process_subprogram);
 }
 
-static int __process_variable(struct state *state, Dwarf_Die *die)
+static int __process_variable(struct state *state, struct die *cache,
+			      Dwarf_Die *die)
 {
-	process("variable ");
-	process_type_attr(state, die);
+	process(cache, "variable ");
+	process_type_attr(state, cache, die);
 	return 0;
 }
 
@@ -287,7 +346,8 @@ static void process_variable(struct state *state, Dwarf_Die *die)
 	process_symbol(state, die, __process_variable);
 }
 
-static int process_exported_symbols(struct state *unused, Dwarf_Die *die)
+static int process_exported_symbols(struct state *unused, struct die *cache,
+				    Dwarf_Die *die)
 {
 	int tag = dwarf_tag(die);
 
@@ -297,7 +357,7 @@ static int process_exported_symbols(struct state *unused, Dwarf_Die *die)
 	case DW_TAG_class_type:
 	case DW_TAG_structure_type:
 		return check(process_die_container(
-			NULL, die, process_exported_symbols, match_all));
+			NULL, cache, die, process_exported_symbols, match_all));
 
 	/* Possible exported symbols */
 	case DW_TAG_subprogram:
@@ -321,6 +381,6 @@ static int process_exported_symbols(struct state *unused, Dwarf_Die *die)
 
 void process_cu(Dwarf_Die *cudie)
 {
-	check(process_die_container(NULL, cudie, process_exported_symbols,
+	check(process_die_container(NULL, NULL, cudie, process_exported_symbols,
 				    match_all));
 }
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index 1763234b6329..7552fde495ef 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -43,6 +43,10 @@ static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
 	debug("%s", name);
 	dbg = dwfl_module_getdwarf(mod, &dwbias);
 
+	/*
+	 * Look for exported symbols in each CU, follow the DIE tree, and add
+	 * the entries to die_map.
+	 */
 	do {
 		res = dwarf_get_units(dbg, cu, &cu, NULL, NULL, &cudie, NULL);
 		if (res < 0)
@@ -53,6 +57,8 @@ static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
 		process_cu(&cudie);
 	} while (cu);
 
+	die_map_free();
+
 	return DWARF_CB_OK;
 }
 
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index cb9fd78a58da..601f877bc8ca 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -87,6 +87,61 @@ void symbol_read_symtab(int fd);
 struct symbol *symbol_get(const char *name);
 void symbol_free(void);
 
+/*
+ * die.c
+ */
+
+enum die_state {
+	DIE_INCOMPLETE,
+	DIE_COMPLETE,
+	DIE_LAST = DIE_COMPLETE
+};
+
+enum die_fragment_type {
+	FRAGMENT_EMPTY,
+	FRAGMENT_STRING,
+	FRAGMENT_DIE
+};
+
+struct die_fragment {
+	enum die_fragment_type type;
+	union {
+		char *str;
+		uintptr_t addr;
+	} data;
+	struct list_head list;
+};
+
+#define CASE_CONST_TO_STR(name) \
+	case name:              \
+		return #name;
+
+static inline const char *die_state_name(enum die_state state)
+{
+	switch (state) {
+	CASE_CONST_TO_STR(DIE_INCOMPLETE)
+	CASE_CONST_TO_STR(DIE_COMPLETE)
+	}
+
+	error("unexpected die_state: %d", state);
+}
+
+struct die {
+	enum die_state state;
+	char *fqn;
+	int tag;
+	uintptr_t addr;
+	struct list_head fragments;
+	struct hlist_node hash;
+};
+
+int __die_map_get(uintptr_t addr, enum die_state state, struct die **res);
+struct die *die_map_get(Dwarf_Die *die, enum die_state state);
+void die_map_add_string(struct die *pd, const char *str);
+void die_map_add_linebreak(struct die *pd, int linebreak);
+void die_map_add_die(struct die *pd, struct die *child);
+void die_map_free(void);
+
 /*
  * dwarf.c
  */
@@ -96,12 +151,14 @@ struct state {
 	Dwarf_Die die;
 };
 
-typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
+typedef int (*die_callback_t)(struct state *state, struct die *cache,
+			      Dwarf_Die *die);
 typedef bool (*die_match_callback_t)(Dwarf_Die *die);
 bool match_all(Dwarf_Die *die);
 
-int process_die_container(struct state *state, Dwarf_Die *die,
-			  die_callback_t func, die_match_callback_t match);
+int process_die_container(struct state *state, struct die *cache,
+			  Dwarf_Die *die, die_callback_t func,
+			  die_match_callback_t match);
 
 void process_cu(Dwarf_Die *cudie);
 
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 05/18] gendwarfksyms: Expand type modifiers and typedefs

[Sami Tolvanen]

Add support for expanding DWARF type modifiers, such as pointers,
const values etc., and typedefs. These types all have DW_AT_type
attribute pointing to the underlying type, and thus produce similar
output.

Also add linebreaks and indentation to debugging output to make it
more readable.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/die.c           | 12 +++++
 scripts/gendwarfksyms/dwarf.c         | 67 +++++++++++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.h |  5 ++
 3 files changed, 84 insertions(+)

diff --git a/scripts/gendwarfksyms/die.c b/scripts/gendwarfksyms/die.c
index b7d900c6a9c8..0d70e02d02b5 100644
--- a/scripts/gendwarfksyms/die.c
+++ b/scripts/gendwarfksyms/die.c
@@ -130,6 +130,18 @@ void die_map_add_string(struct die *cd, const char *str)
 	df->type = FRAGMENT_STRING;
 }
 
+void die_map_add_linebreak(struct die *cd, int linebreak)
+{
+	struct die_fragment *df;
+
+	if (!cd)
+		return;
+
+	df = append_item(cd);
+	df->data.linebreak = linebreak;
+	df->type = FRAGMENT_LINEBREAK;
+}
+
 void die_map_add_die(struct die *cd, struct die *child)
 {
 	struct die_fragment *df;
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index f40e23a547da..3e08a32b7b16 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -7,6 +7,17 @@
 #include <stdarg.h>
 #include "gendwarfksyms.h"
 
+static bool do_linebreak;
+static int indentation_level;
+
+/* Line breaks and indentation for pretty-printing */
+static void process_linebreak(struct die *cache, int n)
+{
+	indentation_level += n;
+	do_linebreak = true;
+	die_map_add_linebreak(cache, n);
+}
+
 #define DEFINE_GET_ATTR(attr, type)                                    \
 	static bool get_##attr##_attr(Dwarf_Die *die, unsigned int id, \
 				      type *value)                     \
@@ -76,6 +87,12 @@ static void process(struct die *cache, const char *s)
 {
 	s = s ?: "<null>";
 
+	if (dump_dies && do_linebreak) {
+		fputs("\n", stderr);
+		for (int i = 0; i < indentation_level; i++)
+			fputs("  ", stderr);
+		do_linebreak = false;
+	}
 	if (dump_dies)
 		fputs(s, stderr);
 
@@ -239,6 +256,40 @@ static void process_type_attr(struct state *state, struct die *cache,
 	process(cache, "base_type void");
 }
 
+/* Container types with DW_AT_type */
+static void __process_type(struct state *state, struct die *cache,
+			   Dwarf_Die *die, const char *type)
+{
+	process(cache, type);
+	process_fqn(cache, die);
+	process(cache, " {");
+	process_linebreak(cache, 1);
+	process_type_attr(state, cache, die);
+	process_linebreak(cache, -1);
+	process(cache, "}");
+	process_byte_size_attr(cache, die);
+	process_alignment_attr(cache, die);
+}
+
+#define DEFINE_PROCESS_TYPE(type)                                            \
+	static void process_##type##_type(struct state *state,               \
+					  struct die *cache, Dwarf_Die *die) \
+	{                                                                    \
+		__process_type(state, cache, die, #type "_type");            \
+	}
+
+DEFINE_PROCESS_TYPE(atomic)
+DEFINE_PROCESS_TYPE(const)
+DEFINE_PROCESS_TYPE(immutable)
+DEFINE_PROCESS_TYPE(packed)
+DEFINE_PROCESS_TYPE(pointer)
+DEFINE_PROCESS_TYPE(reference)
+DEFINE_PROCESS_TYPE(restrict)
+DEFINE_PROCESS_TYPE(rvalue_reference)
+DEFINE_PROCESS_TYPE(shared)
+DEFINE_PROCESS_TYPE(volatile)
+DEFINE_PROCESS_TYPE(typedef)
+
 static void process_base_type(struct state *state, struct die *cache,
 			      Dwarf_Die *die)
 {
@@ -260,6 +311,9 @@ static void process_cached(struct state *state, struct die *cache,
 		case FRAGMENT_STRING:
 			process(NULL, df->data.str);
 			break;
+		case FRAGMENT_LINEBREAK:
+			process_linebreak(NULL, df->data.linebreak);
+			break;
 		case FRAGMENT_DIE:
 			if (!dwarf_die_addr_die(dwarf_cu_getdwarf(die->cu),
 						(void *)df->data.addr, &child))
@@ -295,7 +349,20 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	}
 
 	switch (tag) {
+	/* Type modifiers */
+	PROCESS_TYPE(atomic)
+	PROCESS_TYPE(const)
+	PROCESS_TYPE(immutable)
+	PROCESS_TYPE(packed)
+	PROCESS_TYPE(pointer)
+	PROCESS_TYPE(reference)
+	PROCESS_TYPE(restrict)
+	PROCESS_TYPE(rvalue_reference)
+	PROCESS_TYPE(shared)
+	PROCESS_TYPE(volatile)
+	/* Other types */
 	PROCESS_TYPE(base)
+	PROCESS_TYPE(typedef)
 	default:
 		debug("unimplemented type: %x", tag);
 		break;
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 601f877bc8ca..832d05b4fc1c 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -59,6 +59,9 @@ extern int dump_dies;
 /* Error == negative values */
 #define checkp(expr) __check(expr, __res < 0)
 
+/* Consistent aliases (DW_TAG_<type>_type) for DWARF tags */
+#define DW_TAG_typedef_type DW_TAG_typedef
+
 /*
  * symbols.c
  */
@@ -100,6 +103,7 @@ enum die_state {
 enum die_fragment_type {
 	FRAGMENT_EMPTY,
 	FRAGMENT_STRING,
+	FRAGMENT_LINEBREAK,
 	FRAGMENT_DIE
 };
 
@@ -107,6 +111,7 @@ struct die_fragment {
 	enum die_fragment_type type;
 	union {
 		char *str;
+		int linebreak;
 		uintptr_t addr;
 	} data;
 	struct list_head list;
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 06/18] gendwarfksyms: Expand subroutine_type

[Sami Tolvanen]

Add support for expanding DW_TAG_subroutine_type and the parameters
in DW_TAG_formal_parameter. Use this to also expand subprograms.

Example output with --dump-dies:

  subprogram (
    formal_parameter pointer_type {
      const_type {
        base_type char byte_size(1) encoding(6)
      }
    }
  )
  -> base_type unsigned long byte_size(8) encoding(7)

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c         | 84 ++++++++++++++++++++++++++-
 scripts/gendwarfksyms/gendwarfksyms.h |  4 ++
 2 files changed, 85 insertions(+), 3 deletions(-)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 3e08a32b7b16..7d8a4eb6c387 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -212,6 +212,15 @@ DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
 
+/* Match functions -- die_match_callback_t */
+#define DEFINE_MATCH(type)                                     \
+	static bool match_##type##_type(Dwarf_Die *die)        \
+	{                                                      \
+		return dwarf_tag(die) == DW_TAG_##type##_type; \
+	}
+
+DEFINE_MATCH(formal_parameter)
+
 bool match_all(Dwarf_Die *die)
 {
 	return true;
@@ -224,19 +233,28 @@ int process_die_container(struct state *state, struct die *cache,
 	Dwarf_Die current;
 	int res;
 
+	/* Track the first item in lists. */
+	if (state)
+		state->first_list_item = true;
+
 	res = checkp(dwarf_child(die, &current));
 	while (!res) {
 		if (match(&current)) {
 			/* <0 = error, 0 = continue, >0 = stop */
 			res = checkp(func(state, cache, &current));
 			if (res)
-				return res;
+				goto out;
 		}
 
 		res = checkp(dwarf_siblingof(&current, &current));
 	}
 
-	return 0;
+	res = 0;
+out:
+	if (state)
+		state->first_list_item = false;
+
+	return res;
 }
 
 static int process_type(struct state *state, struct die *parent,
@@ -256,6 +274,40 @@ static void process_type_attr(struct state *state, struct die *cache,
 	process(cache, "base_type void");
 }
 
+static void process_list_comma(struct state *state, struct die *cache)
+{
+	if (state->first_list_item) {
+		state->first_list_item = false;
+	} else {
+		process(cache, " ,");
+		process_linebreak(cache, 0);
+	}
+}
+
+/* Comma-separated with DW_AT_type */
+static void __process_list_type(struct state *state, struct die *cache,
+				Dwarf_Die *die, const char *type)
+{
+	const char *name = get_name_attr(die);
+
+	process_list_comma(state, cache);
+	process(cache, type);
+	process_type_attr(state, cache, die);
+	if (name) {
+		process(cache, " ");
+		process(cache, name);
+	}
+}
+
+#define DEFINE_PROCESS_LIST_TYPE(type)                                       \
+	static void process_##type##_type(struct state *state,               \
+					  struct die *cache, Dwarf_Die *die) \
+	{                                                                    \
+		__process_list_type(state, cache, die, #type " ");           \
+	}
+
+DEFINE_PROCESS_LIST_TYPE(formal_parameter)
+
 /* Container types with DW_AT_type */
 static void __process_type(struct state *state, struct die *cache,
 			   Dwarf_Die *die, const char *type)
@@ -290,6 +342,29 @@ DEFINE_PROCESS_TYPE(shared)
 DEFINE_PROCESS_TYPE(volatile)
 DEFINE_PROCESS_TYPE(typedef)
 
+static void __process_subroutine_type(struct state *state, struct die *cache,
+				      Dwarf_Die *die, const char *type)
+{
+	process(cache, type);
+	process(cache, " (");
+	process_linebreak(cache, 1);
+	/* Parameters */
+	check(process_die_container(state, cache, die, process_type,
+				    match_formal_parameter_type));
+	process_linebreak(cache, -1);
+	process(cache, ")");
+	process_linebreak(cache, 0);
+	/* Return type */
+	process(cache, "-> ");
+	process_type_attr(state, cache, die);
+}
+
+static void process_subroutine_type(struct state *state, struct die *cache,
+				    Dwarf_Die *die)
+{
+	__process_subroutine_type(state, cache, die, "subroutine_type");
+}
+
 static void process_base_type(struct state *state, struct die *cache,
 			      Dwarf_Die *die)
 {
@@ -360,8 +435,11 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	PROCESS_TYPE(rvalue_reference)
 	PROCESS_TYPE(shared)
 	PROCESS_TYPE(volatile)
+	/* Subtypes */
+	PROCESS_TYPE(formal_parameter)
 	/* Other types */
 	PROCESS_TYPE(base)
+	PROCESS_TYPE(subroutine)
 	PROCESS_TYPE(typedef)
 	default:
 		debug("unimplemented type: %x", tag);
@@ -391,7 +469,7 @@ static void process_symbol(struct state *state, Dwarf_Die *die,
 static int __process_subprogram(struct state *state, struct die *cache,
 				Dwarf_Die *die)
 {
-	process(cache, "subprogram");
+	__process_subroutine_type(state, cache, die, "subprogram");
 	return 0;
 }
 
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 832d05b4fc1c..0746a36f4924 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -60,6 +60,7 @@ extern int dump_dies;
 #define checkp(expr) __check(expr, __res < 0)
 
 /* Consistent aliases (DW_TAG_<type>_type) for DWARF tags */
+#define DW_TAG_formal_parameter_type DW_TAG_formal_parameter
 #define DW_TAG_typedef_type DW_TAG_typedef
 
 /*
@@ -154,6 +155,9 @@ void die_map_free(void);
 struct state {
 	struct symbol *sym;
 	Dwarf_Die die;
+
+	/* List expansion */
+	bool first_list_item;
 };
 
 typedef int (*die_callback_t)(struct state *state, struct die *cache,
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 07/18] gendwarfksyms: Expand array_type

[Sami Tolvanen]

Add support for expanding DW_TAG_array_type, and the subrange type
indicating array size.

Example source code:

  const char *s[34];

Output with --dump-dies:

  variable array_type[34] {
    pointer_type {
      const_type {
        base_type char byte_size(1) encoding(6)
      }
    } byte_size(8)
  }

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 7d8a4eb6c387..46ce17b2459b 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -220,6 +220,7 @@ DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
 	}
 
 DEFINE_MATCH(formal_parameter)
+DEFINE_MATCH(subrange)
 
 bool match_all(Dwarf_Die *die)
 {
@@ -342,6 +343,33 @@ DEFINE_PROCESS_TYPE(shared)
 DEFINE_PROCESS_TYPE(volatile)
 DEFINE_PROCESS_TYPE(typedef)
 
+static void process_subrange_type(struct state *state, struct die *cache,
+				  Dwarf_Die *die)
+{
+	Dwarf_Word count = 0;
+
+	if (get_udata_attr(die, DW_AT_count, &count))
+		process_fmt(cache, "[%" PRIu64 "]", count);
+	else if (get_udata_attr(die, DW_AT_upper_bound, &count))
+		process_fmt(cache, "[%" PRIu64 "]", count + 1);
+	else
+		process(cache, "[]");
+}
+
+static void process_array_type(struct state *state, struct die *cache,
+			       Dwarf_Die *die)
+{
+	process(cache, "array_type");
+	/* Array size */
+	check(process_die_container(state, cache, die, process_type,
+				    match_subrange_type));
+	process(cache, " {");
+	process_linebreak(cache, 1);
+	process_type_attr(state, cache, die);
+	process_linebreak(cache, -1);
+	process(cache, "}");
+}
+
 static void __process_subroutine_type(struct state *state, struct die *cache,
 				      Dwarf_Die *die, const char *type)
 {
@@ -437,7 +465,9 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	PROCESS_TYPE(volatile)
 	/* Subtypes */
 	PROCESS_TYPE(formal_parameter)
+	PROCESS_TYPE(subrange)
 	/* Other types */
+	PROCESS_TYPE(array)
 	PROCESS_TYPE(base)
 	PROCESS_TYPE(subroutine)
 	PROCESS_TYPE(typedef)
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 08/18] gendwarfksyms: Expand structure types

[Sami Tolvanen]

Recursively expand DWARF structure types, i.e. structs, unions, and
enums. Also include relevant DWARF attributes in type strings to
encode structure layout, for example.

Example output with --dump-dies:

  subprogram (
    formal_parameter structure_type &str {
      member pointer_type {
        base_type u8 byte_size(1) encoding(7)
      } data_ptr data_member_location(0) ,
      member base_type usize byte_size(8) encoding(7) length data_member_location(8)
    } byte_size(16) alignment(8) msg
  )
  -> base_type void

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c         | 138 +++++++++++++++++++++++++-
 scripts/gendwarfksyms/gendwarfksyms.h |   5 +
 2 files changed, 141 insertions(+), 2 deletions(-)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 46ce17b2459b..6ec1138c459f 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -208,9 +208,14 @@ static void process_fqn(struct die *cache, Dwarf_Die *die)
 				    value);                                \
 	}
 
+DEFINE_PROCESS_UDATA_ATTRIBUTE(accessibility)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(alignment)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(bit_size)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(byte_size)
 DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(data_bit_offset)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(data_member_location)
+DEFINE_PROCESS_UDATA_ATTRIBUTE(discr_value)
 
 /* Match functions -- die_match_callback_t */
 #define DEFINE_MATCH(type)                                     \
@@ -219,7 +224,9 @@ DEFINE_PROCESS_UDATA_ATTRIBUTE(encoding)
 		return dwarf_tag(die) == DW_TAG_##type##_type; \
 	}
 
+DEFINE_MATCH(enumerator)
 DEFINE_MATCH(formal_parameter)
+DEFINE_MATCH(member)
 DEFINE_MATCH(subrange)
 
 bool match_all(Dwarf_Die *die)
@@ -298,6 +305,10 @@ static void __process_list_type(struct state *state, struct die *cache,
 		process(cache, " ");
 		process(cache, name);
 	}
+	process_accessibility_attr(cache, die);
+	process_bit_size_attr(cache, die);
+	process_data_bit_offset_attr(cache, die);
+	process_data_member_location_attr(cache, die);
 }
 
 #define DEFINE_PROCESS_LIST_TYPE(type)                                       \
@@ -308,6 +319,7 @@ static void __process_list_type(struct state *state, struct die *cache,
 	}
 
 DEFINE_PROCESS_LIST_TYPE(formal_parameter)
+DEFINE_PROCESS_LIST_TYPE(member)
 
 /* Container types with DW_AT_type */
 static void __process_type(struct state *state, struct die *cache,
@@ -340,6 +352,7 @@ DEFINE_PROCESS_TYPE(reference)
 DEFINE_PROCESS_TYPE(restrict)
 DEFINE_PROCESS_TYPE(rvalue_reference)
 DEFINE_PROCESS_TYPE(shared)
+DEFINE_PROCESS_TYPE(template_type_parameter)
 DEFINE_PROCESS_TYPE(volatile)
 DEFINE_PROCESS_TYPE(typedef)
 
@@ -393,6 +406,107 @@ static void process_subroutine_type(struct state *state, struct die *cache,
 	__process_subroutine_type(state, cache, die, "subroutine_type");
 }
 
+static void process_variant_type(struct state *state, struct die *cache,
+				 Dwarf_Die *die)
+{
+	process_list_comma(state, cache);
+	process(cache, "variant {");
+	process_linebreak(cache, 1);
+	check(process_die_container(state, cache, die, process_type,
+				    match_member_type));
+	process_linebreak(cache, -1);
+	process(cache, "}");
+	process_discr_value_attr(cache, die);
+}
+
+static void process_variant_part_type(struct state *state, struct die *cache,
+				      Dwarf_Die *die)
+{
+	process_list_comma(state, cache);
+	process(cache, "variant_part {");
+	process_linebreak(cache, 1);
+	check(process_die_container(state, cache, die, process_type,
+				    match_all));
+	process_linebreak(cache, -1);
+	process(cache, "}");
+}
+
+static int ___process_structure_type(struct state *state, struct die *cache,
+				     Dwarf_Die *die)
+{
+	switch (dwarf_tag(die)) {
+	case DW_TAG_member:
+	case DW_TAG_variant_part:
+		return check(process_type(state, cache, die));
+	case DW_TAG_class_type:
+	case DW_TAG_enumeration_type:
+	case DW_TAG_structure_type:
+	case DW_TAG_template_type_parameter:
+	case DW_TAG_union_type:
+	case DW_TAG_subprogram:
+		/* Skip non-member types, including member functions */
+		return 0;
+	default:
+		error("unexpected structure_type child: %x", dwarf_tag(die));
+	}
+}
+
+static void __process_structure_type(struct state *state, struct die *cache,
+				     Dwarf_Die *die, const char *type,
+				     die_callback_t process_func,
+				     die_match_callback_t match_func)
+{
+	process(cache, type);
+	process_fqn(cache, die);
+	process(cache, " {");
+	process_linebreak(cache, 1);
+
+	check(process_die_container(state, cache, die, process_func,
+				    match_func));
+
+	process_linebreak(cache, -1);
+	process(cache, "}");
+
+	process_byte_size_attr(cache, die);
+	process_alignment_attr(cache, die);
+}
+
+#define DEFINE_PROCESS_STRUCTURE_TYPE(structure)                        \
+	static void process_##structure##_type(                         \
+		struct state *state, struct die *cache, Dwarf_Die *die) \
+	{                                                               \
+		__process_structure_type(state, cache, die,             \
+					 #structure "_type",            \
+					 ___process_structure_type,     \
+					 match_all);                    \
+	}
+
+DEFINE_PROCESS_STRUCTURE_TYPE(class)
+DEFINE_PROCESS_STRUCTURE_TYPE(structure)
+DEFINE_PROCESS_STRUCTURE_TYPE(union)
+
+static void process_enumerator_type(struct state *state, struct die *cache,
+				    Dwarf_Die *die)
+{
+	Dwarf_Word value;
+
+	process_list_comma(state, cache);
+	process(cache, "enumerator");
+	process_fqn(cache, die);
+
+	if (get_udata_attr(die, DW_AT_const_value, &value)) {
+		process(cache, " = ");
+		process_fmt(cache, "%" PRIu64, value);
+	}
+}
+
+static void process_enumeration_type(struct state *state, struct die *cache,
+				     Dwarf_Die *die)
+{
+	__process_structure_type(state, cache, die, "enumeration_type",
+				 process_type, match_enumerator_type);
+}
+
 static void process_base_type(struct state *state, struct die *cache,
 			      Dwarf_Die *die)
 {
@@ -403,6 +517,16 @@ static void process_base_type(struct state *state, struct die *cache,
 	process_alignment_attr(cache, die);
 }
 
+static void process_unspecified_type(struct state *state, struct die *cache,
+				     Dwarf_Die *die)
+{
+	/*
+	 * These can be emitted for stand-alone assembly code, which means we
+	 * might run into them in vmlinux.o.
+	 */
+	process(cache, "unspecified_type");
+}
+
 static void process_cached(struct state *state, struct die *cache,
 			   Dwarf_Die *die)
 {
@@ -463,17 +587,27 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	PROCESS_TYPE(rvalue_reference)
 	PROCESS_TYPE(shared)
 	PROCESS_TYPE(volatile)
+	/* Container types */
+	PROCESS_TYPE(class)
+	PROCESS_TYPE(structure)
+	PROCESS_TYPE(union)
+	PROCESS_TYPE(enumeration)
 	/* Subtypes */
+	PROCESS_TYPE(enumerator)
 	PROCESS_TYPE(formal_parameter)
+	PROCESS_TYPE(member)
 	PROCESS_TYPE(subrange)
+	PROCESS_TYPE(template_type_parameter)
+	PROCESS_TYPE(variant)
+	PROCESS_TYPE(variant_part)
 	/* Other types */
 	PROCESS_TYPE(array)
 	PROCESS_TYPE(base)
 	PROCESS_TYPE(subroutine)
 	PROCESS_TYPE(typedef)
+	PROCESS_TYPE(unspecified)
 	default:
-		debug("unimplemented type: %x", tag);
-		break;
+		error("unexpected type: %x", tag);
 	}
 
 	/* Update cache state and append to the parent (if any) */
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 0746a36f4924..1796f71b3a34 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -60,8 +60,13 @@ extern int dump_dies;
 #define checkp(expr) __check(expr, __res < 0)
 
 /* Consistent aliases (DW_TAG_<type>_type) for DWARF tags */
+#define DW_TAG_enumerator_type DW_TAG_enumerator
 #define DW_TAG_formal_parameter_type DW_TAG_formal_parameter
+#define DW_TAG_member_type DW_TAG_member
+#define DW_TAG_template_type_parameter_type DW_TAG_template_type_parameter
 #define DW_TAG_typedef_type DW_TAG_typedef
+#define DW_TAG_variant_part_type DW_TAG_variant_part
+#define DW_TAG_variant_type DW_TAG_variant
 
 /*
  * symbols.c
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 09/18] gendwarfksyms: Limit structure expansion

[Sami Tolvanen]

Expand each structure type only once per exported symbol. This
is necessary to support self-referential structures, which would
otherwise result in infinite recursion, and it's sufficient for
catching ABI changes.

Types defined in .c files are opaque to external users and thus
cannot affect the ABI. Consider type definitions in .c files to
be declarations to prevent opaque types from changing symbol
versions.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/Makefile        |   1 +
 scripts/gendwarfksyms/cache.c         |  51 +++++++++++
 scripts/gendwarfksyms/dwarf.c         | 125 ++++++++++++++++++++++++--
 scripts/gendwarfksyms/gendwarfksyms.h |  46 ++++++++++
 4 files changed, 215 insertions(+), 8 deletions(-)
 create mode 100644 scripts/gendwarfksyms/cache.c

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index c0d4ce50fc27..c06145d84df8 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -2,6 +2,7 @@
 hostprogs-always-y += gendwarfksyms
 
 gendwarfksyms-objs += gendwarfksyms.o
+gendwarfksyms-objs += cache.o
 gendwarfksyms-objs += die.o
 gendwarfksyms-objs += dwarf.o
 gendwarfksyms-objs += symbols.o
diff --git a/scripts/gendwarfksyms/cache.c b/scripts/gendwarfksyms/cache.c
new file mode 100644
index 000000000000..c9c19b86a686
--- /dev/null
+++ b/scripts/gendwarfksyms/cache.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+struct cache_item {
+	unsigned long key;
+	int value;
+	struct hlist_node hash;
+};
+
+void cache_set(struct cache *cache, unsigned long key, int value)
+{
+	struct cache_item *ci;
+
+	ci = xmalloc(sizeof(struct cache_item));
+	ci->key = key;
+	ci->value = value;
+	hash_add(cache->cache, &ci->hash, hash_32(key));
+}
+
+int cache_get(struct cache *cache, unsigned long key)
+{
+	struct cache_item *ci;
+
+	hash_for_each_possible(cache->cache, ci, hash, hash_32(key)) {
+		if (ci->key == key)
+			return ci->value;
+	}
+
+	return -1;
+}
+
+void cache_init(struct cache *cache)
+{
+	hash_init(cache->cache);
+}
+
+void cache_free(struct cache *cache)
+{
+	struct hlist_node *tmp;
+	struct cache_item *ci;
+
+	hash_for_each_safe(cache->cache, ci, tmp, hash) {
+		free(ci);
+	}
+
+	hash_init(cache->cache);
+}
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 6ec1138c459f..6b30e45a4e82 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -27,6 +27,7 @@ static void process_linebreak(struct die *cache, int n)
 		       !dwarf_form##attr(&da, value);                  \
 	}
 
+DEFINE_GET_ATTR(flag, bool)
 DEFINE_GET_ATTR(udata, Dwarf_Word)
 
 static bool get_ref_die_attr(Dwarf_Die *die, unsigned int id, Dwarf_Die *value)
@@ -80,6 +81,55 @@ static bool match_export_symbol(struct state *state, Dwarf_Die *die)
 	return !!state->sym;
 }
 
+/* DW_AT_decl_file -> struct srcfile */
+static struct cache srcfile_cache;
+
+static bool is_definition_private(Dwarf_Die *die)
+{
+	Dwarf_Word filenum;
+	Dwarf_Files *files;
+	Dwarf_Die cudie;
+	const char *s;
+	int res;
+
+	/*
+	 * Definitions in .c files cannot change the public ABI,
+	 * so consider them private.
+	 */
+	if (!get_udata_attr(die, DW_AT_decl_file, &filenum))
+		return false;
+
+	res = cache_get(&srcfile_cache, filenum);
+	if (res >= 0)
+		return !!res;
+
+	if (!dwarf_cu_die(die->cu, &cudie, NULL, NULL, NULL, NULL, NULL, NULL))
+		error("dwarf_cu_die failed: '%s'", dwarf_errmsg(-1));
+
+	if (dwarf_getsrcfiles(&cudie, &files, NULL))
+		error("dwarf_getsrcfiles failed: '%s'", dwarf_errmsg(-1));
+
+	s = dwarf_filesrc(files, filenum, NULL, NULL);
+	if (!s)
+		error("dwarf_filesrc failed: '%s'", dwarf_errmsg(-1));
+
+	s = strrchr(s, '.');
+	res = s && !strcmp(s, ".c");
+	cache_set(&srcfile_cache, filenum, res);
+
+	return !!res;
+}
+
+static bool is_kabi_definition(Dwarf_Die *die)
+{
+	bool value;
+
+	if (get_flag_attr(die, DW_AT_declaration, &value) && value)
+		return false;
+
+	return !is_definition_private(die);
+}
+
 /*
  * Type string processing
  */
@@ -456,19 +506,27 @@ static void __process_structure_type(struct state *state, struct die *cache,
 				     die_callback_t process_func,
 				     die_match_callback_t match_func)
 {
+	bool expand;
+
 	process(cache, type);
 	process_fqn(cache, die);
 	process(cache, " {");
 	process_linebreak(cache, 1);
 
-	check(process_die_container(state, cache, die, process_func,
-				    match_func));
+	expand = state->expand.expand && is_kabi_definition(die);
+
+	if (expand) {
+		check(process_die_container(state, cache, die, process_func,
+					    match_func));
+	}
 
 	process_linebreak(cache, -1);
 	process(cache, "}");
 
-	process_byte_size_attr(cache, die);
-	process_alignment_attr(cache, die);
+	if (expand) {
+		process_byte_size_attr(cache, die);
+		process_alignment_attr(cache, die);
+	}
 }
 
 #define DEFINE_PROCESS_STRUCTURE_TYPE(structure)                        \
@@ -553,6 +611,30 @@ static void process_cached(struct state *state, struct die *cache,
 	}
 }
 
+static void state_init(struct state *state)
+{
+	state->expand.expand = true;
+	cache_init(&state->expansion_cache);
+}
+
+static void expansion_state_restore(struct expansion_state *state,
+				    struct expansion_state *saved)
+{
+	state->expand = saved->expand;
+}
+
+static void expansion_state_save(struct expansion_state *state,
+				 struct expansion_state *saved)
+{
+	expansion_state_restore(saved, state);
+}
+
+static bool is_expanded_type(int tag)
+{
+	return tag == DW_TAG_class_type || tag == DW_TAG_structure_type ||
+	       tag == DW_TAG_union_type || tag == DW_TAG_enumeration_type;
+}
+
 #define PROCESS_TYPE(type)                                \
 	case DW_TAG_##type##_type:                        \
 		process_##type##_type(state, cache, die); \
@@ -560,18 +642,39 @@ static void process_cached(struct state *state, struct die *cache,
 
 static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 {
+	enum die_state want_state = DIE_COMPLETE;
 	struct die *cache;
+	struct expansion_state saved;
 	int tag = dwarf_tag(die);
 
+	expansion_state_save(&state->expand, &saved);
+
 	/*
-	 * If we have the DIE already cached, use it instead of walking
+	 * Structures and enumeration types are expanded only once per
+	 * exported symbol. This is sufficient for detecting ABI changes
+	 * within the structure.
+	 */
+	if (is_expanded_type(tag)) {
+		if (cache_was_expanded(&state->expansion_cache, die->addr))
+			state->expand.expand = false;
+
+		if (state->expand.expand)
+			cache_mark_expanded(&state->expansion_cache, die->addr);
+		else
+			want_state = DIE_UNEXPANDED;
+	}
+
+	/*
+	 * If we have want_state already cached, use it instead of walking
 	 * through DWARF.
 	 */
-	cache = die_map_get(die, DIE_COMPLETE);
+	cache = die_map_get(die, want_state);
 
-	if (cache->state == DIE_COMPLETE) {
+	if (cache->state == want_state) {
 		process_cached(state, cache, die);
 		die_map_add_die(parent, cache);
+
+		expansion_state_restore(&state->expand, &saved);
 		return 0;
 	}
 
@@ -612,9 +715,10 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 
 	/* Update cache state and append to the parent (if any) */
 	cache->tag = tag;
-	cache->state = DIE_COMPLETE;
+	cache->state = want_state;
 	die_map_add_die(parent, cache);
 
+	expansion_state_restore(&state->expand, &saved);
 	return 0;
 }
 
@@ -676,11 +780,14 @@ static int process_exported_symbols(struct state *unused, struct die *cache,
 		if (!match_export_symbol(&state, die))
 			return 0;
 
+		state_init(&state);
+
 		if (tag == DW_TAG_subprogram)
 			process_subprogram(&state, &state.die);
 		else
 			process_variable(&state, &state.die);
 
+		cache_free(&state.expansion_cache);
 		return 0;
 	}
 	default:
@@ -692,4 +799,6 @@ void process_cu(Dwarf_Die *cudie)
 {
 	check(process_die_container(NULL, NULL, cudie, process_exported_symbols,
 				    match_all));
+
+	cache_free(&srcfile_cache);
 }
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 1796f71b3a34..941c4134da8e 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -102,6 +102,7 @@ void symbol_free(void);
 
 enum die_state {
 	DIE_INCOMPLETE,
+	DIE_UNEXPANDED,
 	DIE_COMPLETE,
 	DIE_LAST = DIE_COMPLETE
 };
@@ -131,6 +132,7 @@ static inline const char *die_state_name(enum die_state state)
 {
 	switch (state) {
 	CASE_CONST_TO_STR(DIE_INCOMPLETE)
+	CASE_CONST_TO_STR(DIE_UNEXPANDED)
 	CASE_CONST_TO_STR(DIE_COMPLETE)
 	}
 
@@ -153,16 +155,60 @@ void die_map_add_linebreak(struct die *pd, int linebreak);
 void die_map_add_die(struct die *pd, struct die *child);
 void die_map_free(void);
 
+/*
+ * cache.c
+ */
+
+#define CACHE_HASH_BITS 10
+
+/* A cache for addresses we've already seen. */
+struct cache {
+	HASHTABLE_DECLARE(cache, 1 << CACHE_HASH_BITS);
+};
+
+void cache_set(struct cache *cache, unsigned long key, int value);
+int cache_get(struct cache *cache, unsigned long key);
+void cache_init(struct cache *cache);
+void cache_free(struct cache *cache);
+
+static inline void __cache_mark_expanded(struct cache *cache, uintptr_t addr)
+{
+	cache_set(cache, addr, 1);
+}
+
+static inline bool __cache_was_expanded(struct cache *cache, uintptr_t addr)
+{
+	return cache_get(cache, addr) == 1;
+}
+
+static inline void cache_mark_expanded(struct cache *cache, void *addr)
+{
+	__cache_mark_expanded(cache, (uintptr_t)addr);
+}
+
+static inline bool cache_was_expanded(struct cache *cache, void *addr)
+{
+	return __cache_was_expanded(cache, (uintptr_t)addr);
+}
+
 /*
  * dwarf.c
  */
 
+struct expansion_state {
+	bool expand;
+};
+
 struct state {
 	struct symbol *sym;
 	Dwarf_Die die;
 
 	/* List expansion */
 	bool first_list_item;
+
+	/* Structure expansion */
+	struct expansion_state expand;
+	struct cache expansion_cache;
 };
 
 typedef int (*die_callback_t)(struct state *state, struct die *cache,
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 10/18] gendwarfksyms: Add die_map debugging

[Sami Tolvanen]

Debugging the DWARF processing can be somewhat challenging, so add
more detailed debugging output for die_map operations. Add the
--dump-die-map flag, which adds color coded tags to the output for
die_map changes.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c         | 15 +++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.c |  7 +++++++
 scripts/gendwarfksyms/gendwarfksyms.h | 13 +++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 6b30e45a4e82..364ff4892d5c 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -146,6 +146,8 @@ static void process(struct die *cache, const char *s)
 	if (dump_dies)
 		fputs(s, stderr);
 
+	if (cache)
+		die_debug_r("cache %p string '%s'", cache, s);
 	die_map_add_string(cache, s);
 }
 
@@ -594,6 +596,8 @@ static void process_cached(struct state *state, struct die *cache,
 	list_for_each_entry(df, &cache->fragments, list) {
 		switch (df->type) {
 		case FRAGMENT_STRING:
+			die_debug_b("cache %p STRING '%s'", cache,
+				    df->data.str);
 			process(NULL, df->data.str);
 			break;
 		case FRAGMENT_LINEBREAK:
@@ -603,6 +607,8 @@ static void process_cached(struct state *state, struct die *cache,
 			if (!dwarf_die_addr_die(dwarf_cu_getdwarf(die->cu),
 						(void *)df->data.addr, &child))
 				error("dwarf_die_addr_die failed");
+			die_debug_b("cache %p DIE addr %" PRIxPTR " tag %x",
+				    cache, df->data.addr, dwarf_tag(&child));
 			check(process_type(state, NULL, &child));
 			break;
 		default:
@@ -671,6 +677,9 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 	cache = die_map_get(die, want_state);
 
 	if (cache->state == want_state) {
+		die_debug_g("cached addr %p tag %x -- %s", die->addr, tag,
+			    die_state_name(cache->state));
+
 		process_cached(state, cache, die);
 		die_map_add_die(parent, cache);
 
@@ -678,6 +687,9 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 		return 0;
 	}
 
+	die_debug_g("addr %p tag %x -- %s -> %s", die->addr, tag,
+		    die_state_name(cache->state), die_state_name(want_state));
+
 	switch (tag) {
 	/* Type modifiers */
 	PROCESS_TYPE(atomic)
@@ -713,6 +725,9 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 		error("unexpected type: %x", tag);
 	}
 
+	die_debug_r("parent %p cache %p die addr %p tag %x", parent, cache,
+		    die->addr, tag);
+
 	/* Update cache state and append to the parent (if any) */
 	cache->tag = tag;
 	cache->state = want_state;
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index 7552fde495ef..ed6d8c585268 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -19,6 +19,8 @@
 int debug;
 /* Dump DIE contents */
 int dump_dies;
+/* Print debugging information about die_map changes */
+int dump_die_map;
 
 static void usage(void)
 {
@@ -26,6 +28,7 @@ static void usage(void)
 	      "Options:\n"
 	      "  -d, --debug          Print debugging information\n"
 	      "      --dump-dies      Dump DWARF DIE contents\n"
+	      "      --dump-die-map   Print debugging information about die_map changes\n"
 	      "  -h, --help           Print this message\n"
 	      "\n",
 	      stderr);
@@ -74,6 +77,7 @@ int main(int argc, char **argv)
 
 	struct option opts[] = { { "debug", 0, NULL, 'd' },
 				 { "dump-dies", 0, &dump_dies, 1 },
+				 { "dump-die-map", 0, &dump_die_map, 1 },
 				 { "help", 0, NULL, 'h' },
 				 { 0, 0, NULL, 0 } };
 
@@ -93,6 +97,9 @@ int main(int argc, char **argv)
 		}
 	}
 
+	if (dump_die_map)
+		dump_dies = 1;
+
 	if (optind >= argc) {
 		usage();
 		error("no input files?");
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 941c4134da8e..251832dac599 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -21,6 +21,7 @@
  */
 extern int debug;
 extern int dump_dies;
+extern int dump_die_map;
 
 /*
  * Output helpers
@@ -43,6 +44,18 @@ extern int dump_dies;
 		exit(1);                                     \
 	} while (0)
 
+#define __die_debug(color, format, ...)                                 \
+	do {                                                            \
+		if (dump_dies && dump_die_map)                          \
+			fprintf(stderr,                                 \
+				"\033[" #color "m<" format ">\033[39m", \
+				__VA_ARGS__);                           \
+	} while (0)
+
+#define die_debug_r(format, ...) __die_debug(91, format, __VA_ARGS__)
+#define die_debug_g(format, ...) __die_debug(92, format, __VA_ARGS__)
+#define die_debug_b(format, ...) __die_debug(94, format, __VA_ARGS__)
+
 /*
  * Error handling helpers
  */
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 11/18] gendwarfksyms: Add symtypes output

[Sami Tolvanen]

Add support for producing genksyms-style symtypes files. Process
die_map to find the longest expansions for each type, and use symtypes
references in type definitions. The basic file format is similar to
genksyms, with two notable exceptions:

  1. Type names with spaces (common with Rust) in references are
     wrapped in single quotes. E.g.:

     s#'core::result::Result<u8, core::num::error::ParseIntError>'

  2. The actual type definition is the simple parsed DWARF format we
     output with --dump-dies, not the preprocessed C-style format
     genksyms produces.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/Makefile        |   1 +
 scripts/gendwarfksyms/die.c           |  11 +
 scripts/gendwarfksyms/dwarf.c         |   1 +
 scripts/gendwarfksyms/gendwarfksyms.c |  33 ++-
 scripts/gendwarfksyms/gendwarfksyms.h |  19 ++
 scripts/gendwarfksyms/symbols.c       |   4 +-
 scripts/gendwarfksyms/types.c         | 363 ++++++++++++++++++++++++++
 7 files changed, 429 insertions(+), 3 deletions(-)
 create mode 100644 scripts/gendwarfksyms/types.c

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index c06145d84df8..6540282dc746 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -6,5 +6,6 @@ gendwarfksyms-objs += cache.o
 gendwarfksyms-objs += die.o
 gendwarfksyms-objs += dwarf.o
 gendwarfksyms-objs += symbols.o
+gendwarfksyms-objs += types.o
 
 HOSTLDLIBS_gendwarfksyms := -ldw -lelf
diff --git a/scripts/gendwarfksyms/die.c b/scripts/gendwarfksyms/die.c
index 0d70e02d02b5..66bd4c9bc952 100644
--- a/scripts/gendwarfksyms/die.c
+++ b/scripts/gendwarfksyms/die.c
@@ -22,6 +22,7 @@ static inline unsigned int die_hash(uintptr_t addr, enum die_state state)
 static void init_die(struct die *cd)
 {
 	cd->state = DIE_INCOMPLETE;
+	cd->mapped = false;
 	cd->fqn = NULL;
 	cd->tag = -1;
 	cd->addr = 0;
@@ -83,6 +84,16 @@ static void reset_die(struct die *cd)
 	init_die(cd);
 }
 
+void die_map_for_each(die_map_callback_t func, void *arg)
+{
+	struct hlist_node *tmp;
+	struct die *cd;
+
+	hash_for_each_safe(die_map, cd, tmp, hash) {
+		func(cd, arg);
+	}
+}
+
 void die_map_free(void)
 {
 	struct hlist_node *tmp;
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 364ff4892d5c..a9966a23167a 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -745,6 +745,7 @@ static void process_symbol(struct state *state, Dwarf_Die *die,
 {
 	debug("%s", state->sym->name);
 	check(process_func(state, NULL, die));
+	state->sym->state = SYMBOL_MAPPED;
 	if (dump_dies)
 		fputs("\n", stderr);
 }
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index ed6d8c585268..76a38b733ad2 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -21,6 +21,11 @@ int debug;
 int dump_dies;
 /* Print debugging information about die_map changes */
 int dump_die_map;
+/* Print out type strings (i.e. type_map) */
+int dump_types;
+/* Write a symtypes file */
+int symtypes;
+static const char *symtypes_file;
 
 static void usage(void)
 {
@@ -29,6 +34,8 @@ static void usage(void)
 	      "  -d, --debug          Print debugging information\n"
 	      "      --dump-dies      Dump DWARF DIE contents\n"
 	      "      --dump-die-map   Print debugging information about die_map changes\n"
+	      "      --dump-types     Dump type strings\n"
+	      "  -T, --symtypes file  Write a symtypes file\n"
 	      "  -h, --help           Print this message\n"
 	      "\n",
 	      stderr);
@@ -41,6 +48,7 @@ static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
 	Dwarf_Die cudie;
 	Dwarf_CU *cu = NULL;
 	Dwarf *dbg;
+	FILE *symfile = arg;
 	int res;
 
 	debug("%s", name);
@@ -60,6 +68,10 @@ static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
 		process_cu(&cudie);
 	} while (cu);
 
+	/*
+	 * Use die_map to expand type strings and write them to `symfile`.
+	 */
+	generate_symtypes(symfile);
 	die_map_free();
 
 	return DWARF_CB_OK;
@@ -72,22 +84,29 @@ static const Dwfl_Callbacks callbacks = {
 
 int main(int argc, char **argv)
 {
+	FILE *symfile = NULL;
 	unsigned int n;
 	int opt;
 
 	struct option opts[] = { { "debug", 0, NULL, 'd' },
 				 { "dump-dies", 0, &dump_dies, 1 },
 				 { "dump-die-map", 0, &dump_die_map, 1 },
+				 { "dump-types", 0, &dump_types, 1 },
+				 { "symtypes", 1, NULL, 'T' },
 				 { "help", 0, NULL, 'h' },
 				 { 0, 0, NULL, 0 } };
 
-	while ((opt = getopt_long(argc, argv, "dh", opts, NULL)) != EOF) {
+	while ((opt = getopt_long(argc, argv, "dT:h", opts, NULL)) != EOF) {
 		switch (opt) {
 		case 0:
 			break;
 		case 'd':
 			debug = 1;
 			break;
+		case 'T':
+			symtypes = 1;
+			symtypes_file = optarg;
+			break;
 		case 'h':
 			usage();
 			return 0;
@@ -107,6 +126,13 @@ int main(int argc, char **argv)
 
 	symbol_read_exports(stdin);
 
+	if (symtypes_file) {
+		symfile = fopen(symtypes_file, "w");
+		if (!symfile)
+			error("fopen failed for '%s': %s", symtypes_file,
+			      strerror(errno));
+	}
+
 	for (n = optind; n < argc; n++) {
 		Dwfl *dwfl;
 		int fd;
@@ -129,12 +155,15 @@ int main(int argc, char **argv)
 
 		dwfl_report_end(dwfl, NULL, NULL);
 
-		if (dwfl_getmodules(dwfl, &process_module, NULL, 0))
+		if (dwfl_getmodules(dwfl, &process_module, symfile, 0))
 			error("dwfl_getmodules failed for '%s'", argv[n]);
 
 		dwfl_end(dwfl);
 	}
 
+	if (symfile)
+		check(fclose(symfile));
+
 	symbol_free();
 
 	return 0;
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 251832dac599..98d5b2315f21 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -22,6 +22,8 @@
 extern int debug;
 extern int dump_dies;
 extern int dump_die_map;
+extern int dump_types;
+extern int symtypes;
 
 /*
  * Output helpers
@@ -90,6 +92,11 @@ static inline unsigned int addr_hash(uintptr_t addr)
 	return hash_ptr((const void *)addr);
 }
 
+enum symbol_state {
+	SYMBOL_UNPROCESSED,
+	SYMBOL_MAPPED,
+};
+
 struct symbol_addr {
 	uint32_t section;
 	Elf64_Addr address;
@@ -100,6 +107,8 @@ struct symbol {
 	struct symbol_addr addr;
 	struct hlist_node addr_hash;
 	struct hlist_node name_hash;
+	enum symbol_state state;
+	uintptr_t die_addr;
 };
 
 typedef void (*symbol_callback_t)(struct symbol *, void *arg);
@@ -154,6 +163,7 @@ static inline const char *die_state_name(enum die_state state)
 
 struct die {
 	enum die_state state;
+	bool mapped;
 	char *fqn;
 	int tag;
 	uintptr_t addr;
@@ -161,10 +171,13 @@ struct die {
 	struct hlist_node hash;
 };
 
+typedef void (*die_map_callback_t)(struct die *, void *arg);
+
 int __die_map_get(uintptr_t addr, enum die_state state, struct die **res);
 struct die *die_map_get(Dwarf_Die *die, enum die_state state);
 void die_map_add_string(struct die *pd, const char *str);
 void die_map_add_linebreak(struct die *pd, int linebreak);
+void die_map_for_each(die_map_callback_t func, void *arg);
 void die_map_add_die(struct die *pd, struct die *child);
 void die_map_free(void);
 
@@ -235,4 +248,10 @@ int process_die_container(struct state *state, struct die *cache,
 
 void process_cu(Dwarf_Die *cudie);
 
+/*
+ * types.c
+ */
+
+void generate_symtypes(FILE *file);
+
 #endif /* __GENDWARFKSYMS_H */
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
index 98febb524dd5..0d2ce7284a53 100644
--- a/scripts/gendwarfksyms/symbols.c
+++ b/scripts/gendwarfksyms/symbols.c
@@ -92,6 +92,7 @@ void symbol_read_exports(FILE *file)
 		sym = xcalloc(1, sizeof(struct symbol));
 		sym->name = name;
 		sym->addr.section = SHN_UNDEF;
+		sym->state = SYMBOL_UNPROCESSED;
 
 		hash_add(symbol_names, &sym->name_hash, hash_str(sym->name));
 		++nsym;
@@ -107,7 +108,8 @@ static void get_symbol(struct symbol *sym, void *arg)
 {
 	struct symbol **res = arg;
 
-	*res = sym;
+	if (sym->state == SYMBOL_UNPROCESSED)
+		*res = sym;
 }
 
 struct symbol *symbol_get(const char *name)
diff --git a/scripts/gendwarfksyms/types.c b/scripts/gendwarfksyms/types.c
new file mode 100644
index 000000000000..21d7a34228eb
--- /dev/null
+++ b/scripts/gendwarfksyms/types.c
@@ -0,0 +1,363 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#define _GNU_SOURCE
+#include <inttypes.h>
+#include <stdio.h>
+
+#include "gendwarfksyms.h"
+
+static struct cache expansion_cache;
+
+/*
+ * A simple linked list of shared or owned strings to avoid copying strings
+ * around when not necessary.
+ */
+struct type_list_entry {
+	const char *str;
+	void *owned;
+	struct list_head list;
+};
+
+static void type_list_free(struct list_head *list)
+{
+	struct type_list_entry *entry;
+	struct type_list_entry *tmp;
+
+	list_for_each_entry_safe(entry, tmp, list, list) {
+		if (entry->owned)
+			free(entry->owned);
+		free(entry);
+	}
+
+	INIT_LIST_HEAD(list);
+}
+
+static int type_list_append(struct list_head *list, const char *s, void *owned)
+{
+	struct type_list_entry *entry;
+
+	if (!s)
+		return 0;
+
+	entry = xmalloc(sizeof(struct type_list_entry));
+	entry->str = s;
+	entry->owned = owned;
+	list_add_tail(&entry->list, list);
+
+	return strlen(entry->str);
+}
+
+static void type_list_write(struct list_head *list, FILE *file)
+{
+	struct type_list_entry *entry;
+
+	list_for_each_entry(entry, list, list) {
+		if (entry->str)
+			checkp(fputs(entry->str, file));
+	}
+}
+
+/*
+ * An expanded type string in symtypes format.
+ */
+struct type_expansion {
+	char *name;
+	size_t len;
+	struct list_head expanded;
+	struct hlist_node hash;
+};
+
+static void type_expansion_init(struct type_expansion *type)
+{
+	type->name = NULL;
+	type->len = 0;
+	INIT_LIST_HEAD(&type->expanded);
+}
+
+static inline void type_expansion_free(struct type_expansion *type)
+{
+	free(type->name);
+	type->name = NULL;
+	type->len = 0;
+	type_list_free(&type->expanded);
+}
+
+static void type_expansion_append(struct type_expansion *type, const char *s,
+				  void *owned)
+{
+	type->len += type_list_append(&type->expanded, s, owned);
+}
+
+/*
+ * type_map -- the longest expansions for each type.
+ *
+ * const char *name -> struct type_expansion *
+ */
+#define TYPE_HASH_BITS 12
+static HASHTABLE_DEFINE(type_map, 1 << TYPE_HASH_BITS);
+
+static int type_map_get(const char *name, struct type_expansion **res)
+{
+	struct type_expansion *e;
+
+	hash_for_each_possible(type_map, e, hash, hash_str(name)) {
+		if (!strcmp(name, e->name)) {
+			*res = e;
+			return 0;
+		}
+	}
+
+	return -1;
+}
+
+static void type_map_add(const char *name, struct type_expansion *type)
+{
+	struct type_expansion *e;
+
+	if (type_map_get(name, &e)) {
+		e = xmalloc(sizeof(struct type_expansion));
+		type_expansion_init(e);
+		e->name = xstrdup(name);
+
+		hash_add(type_map, &e->hash, hash_str(e->name));
+
+		if (dump_types)
+			debug("adding %s", e->name);
+	} else {
+		/* Use the longest available expansion */
+		if (type->len <= e->len)
+			return;
+
+		type_list_free(&e->expanded);
+
+		if (dump_types)
+			debug("replacing %s", e->name);
+	}
+
+	/* Take ownership of type->expanded */
+	list_replace_init(&type->expanded, &e->expanded);
+	e->len = type->len;
+
+	if (dump_types) {
+		checkp(fputs(e->name, stderr));
+		checkp(fputs(" ", stderr));
+		type_list_write(&e->expanded, stderr);
+		checkp(fputs("\n", stderr));
+	}
+}
+
+static void type_map_write(FILE *file)
+{
+	struct type_expansion *e;
+	struct hlist_node *tmp;
+
+	if (!file)
+		return;
+
+	hash_for_each_safe(type_map, e, tmp, hash) {
+		checkp(fputs(e->name, file));
+		checkp(fputs(" ", file));
+		type_list_write(&e->expanded, file);
+		checkp(fputs("\n", file));
+	}
+}
+
+static void type_map_free(void)
+{
+	struct type_expansion *e;
+	struct hlist_node *tmp;
+
+	hash_for_each_safe(type_map, e, tmp, hash) {
+		type_expansion_free(e);
+		free(e);
+	}
+
+	hash_init(type_map);
+}
+
+/*
+ * Type reference format: <prefix>#<name>, where prefix:
+ * 	s -> structure
+ * 	u -> union
+ * 	e -> enum
+ * 	t -> typedef
+ *
+ * Names with spaces are additionally wrapped in single quotes.
+ */
+static char get_type_prefix(int tag)
+{
+	switch (tag) {
+	case DW_TAG_class_type:
+	case DW_TAG_structure_type:
+		return 's';
+	case DW_TAG_union_type:
+		return 'u';
+	case DW_TAG_enumeration_type:
+		return 'e';
+	case DW_TAG_typedef_type:
+		return 't';
+	default:
+		return 0;
+	}
+}
+
+static char *get_type_name(struct die *cache)
+{
+	const char *quote;
+	char prefix;
+	char *name;
+
+	if (cache->state == DIE_INCOMPLETE) {
+		warn("found incomplete cache entry: %p", cache);
+		return NULL;
+	}
+	if (!cache->fqn || !*cache->fqn)
+		return NULL;
+
+	prefix = get_type_prefix(cache->tag);
+	if (!prefix)
+		return NULL;
+
+	/* Wrap names with spaces in single quotes */
+	quote = strstr(cache->fqn, " ") ? "'" : "";
+
+	/* <prefix>#<type_name>\0 */
+	if (asprintf(&name, "%c#%s%s%s", prefix, quote, cache->fqn, quote) < 0)
+		error("asprintf failed for '%s'", cache->fqn);
+
+	return name;
+}
+
+static void __type_expand(struct die *cache, struct type_expansion *type,
+			  bool recursive);
+
+static void type_expand_child(struct die *cache, struct type_expansion *type,
+			      bool recursive)
+{
+	struct type_expansion child;
+	char *name;
+
+	name = get_type_name(cache);
+	if (!name) {
+		__type_expand(cache, type, recursive);
+		return;
+	}
+
+	if (recursive && !__cache_was_expanded(&expansion_cache, cache->addr)) {
+		__cache_mark_expanded(&expansion_cache, cache->addr);
+		type_expansion_init(&child);
+		__type_expand(cache, &child, true);
+		type_map_add(name, &child);
+		type_expansion_free(&child);
+	}
+
+	type_expansion_append(type, name, name);
+}
+
+static void __type_expand(struct die *cache, struct type_expansion *type,
+			  bool recursive)
+{
+	struct die_fragment *df;
+	struct die *child;
+
+	list_for_each_entry(df, &cache->fragments, list) {
+		switch (df->type) {
+		case FRAGMENT_STRING:
+			type_expansion_append(type, df->data.str, NULL);
+			break;
+		case FRAGMENT_DIE:
+			/* Use a complete die_map expansion if available */
+			if (__die_map_get(df->data.addr, DIE_COMPLETE,
+					  &child) &&
+			    __die_map_get(df->data.addr, DIE_UNEXPANDED,
+					  &child))
+				error("unknown child: %" PRIxPTR,
+				      df->data.addr);
+
+			type_expand_child(child, type, recursive);
+			break;
+		case FRAGMENT_LINEBREAK:
+			/*
+			 * Keep whitespace in the symtypes format, but avoid
+			 * repeated spaces.
+			 */
+			if (list_is_last(&df->list, &cache->fragments) ||
+			    list_next_entry(df, list)->type !=
+				    FRAGMENT_LINEBREAK)
+				type_expansion_append(type, " ", NULL);
+			break;
+		default:
+			error("empty die_fragment in %p", cache);
+		}
+	}
+}
+
+static void type_expand(struct die *cache, struct type_expansion *type,
+			bool recursive)
+{
+	type_expansion_init(type);
+	__type_expand(cache, type, recursive);
+	cache_free(&expansion_cache);
+}
+
+static void expand_type(struct die *cache, void *arg)
+{
+	struct type_expansion type;
+	char *name;
+
+	if (cache->mapped)
+		return;
+
+	cache->mapped = true;
+
+	/*
+	 * Skip unexpanded die_map entries if there's a complete
+	 * expansion available for this DIE.
+	 */
+	if (cache->state == DIE_UNEXPANDED &&
+	    !__die_map_get(cache->addr, DIE_COMPLETE, &cache)) {
+		if (cache->mapped)
+			return;
+
+		cache->mapped = true;
+	}
+
+	name = get_type_name(cache);
+	if (!name)
+		return;
+
+	debug("%s", name);
+	type_expand(cache, &type, true);
+	type_map_add(name, &type);
+
+	type_expansion_free(&type);
+	free(name);
+}
+
+void generate_symtypes(FILE *file)
+{
+	cache_init(&expansion_cache);
+
+	/*
+	 * die_map processing:
+	 *
+	 *   1. die_map contains all types referenced in exported symbol
+	 *      signatures, but can contain duplicates just like the original
+	 *      DWARF, and some references may not be fully expanded depending
+	 *      on how far we processed the DIE tree for that specific symbol.
+	 *
+	 *      For each die_map entry, find the longest available expansion,
+	 *      and add it to type_map.
+	 */
+	die_map_for_each(expand_type, NULL);
+
+	/*
+	 *   2. If a symtypes file is requested, write type_map contents to
+	 *      the file.
+	 */
+	type_map_write(file);
+	type_map_free();
+}
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 12/18] gendwarfksyms: Add symbol versioning

[Sami Tolvanen]

Calculate symbol versions from the fully expanded type strings in
type_map, and output the versions in a genksyms-compatible format.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/Makefile        |   2 +-
 scripts/gendwarfksyms/dwarf.c         |  25 +++++-
 scripts/gendwarfksyms/gendwarfksyms.c |  10 ++-
 scripts/gendwarfksyms/gendwarfksyms.h |  13 ++-
 scripts/gendwarfksyms/symbols.c       |  53 +++++++++++
 scripts/gendwarfksyms/types.c         | 122 +++++++++++++++++++++++++-
 6 files changed, 216 insertions(+), 9 deletions(-)

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index 6540282dc746..e889b958957b 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -8,4 +8,4 @@ gendwarfksyms-objs += dwarf.o
 gendwarfksyms-objs += symbols.o
 gendwarfksyms-objs += types.o
 
-HOSTLDLIBS_gendwarfksyms := -ldw -lelf
+HOSTLDLIBS_gendwarfksyms := -ldw -lelf -lz
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index a9966a23167a..bdf899d60707 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -740,12 +740,33 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 /*
  * Exported symbol processing
  */
+static struct die *get_symbol_cache(struct state *state, Dwarf_Die *die)
+{
+	struct die *cache;
+
+	cache = die_map_get(die, DIE_SYMBOL);
+
+	if (cache->state != DIE_INCOMPLETE)
+		return NULL; /* We already processed a symbol for this DIE */
+
+	cache->tag = dwarf_tag(die);
+	return cache;
+}
+
 static void process_symbol(struct state *state, Dwarf_Die *die,
 			   die_callback_t process_func)
 {
+	struct die *cache;
+
+	symbol_set_die(state->sym, die);
+
+	cache = get_symbol_cache(state, die);
+	if (!cache)
+		return;
+
 	debug("%s", state->sym->name);
-	check(process_func(state, NULL, die));
-	state->sym->state = SYMBOL_MAPPED;
+	check(process_func(state, cache, die));
+	cache->state = DIE_SYMBOL;
 	if (dump_dies)
 		fputs("\n", stderr);
 }
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index 76a38b733ad2..fd2429ea198f 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -23,6 +23,8 @@ int dump_dies;
 int dump_die_map;
 /* Print out type strings (i.e. type_map) */
 int dump_types;
+/* Print out expanded type strings used for symbol versions */
+int dump_versions;
 /* Write a symtypes file */
 int symtypes;
 static const char *symtypes_file;
@@ -35,6 +37,7 @@ static void usage(void)
 	      "      --dump-dies      Dump DWARF DIE contents\n"
 	      "      --dump-die-map   Print debugging information about die_map changes\n"
 	      "      --dump-types     Dump type strings\n"
+	      "      --dump-versions  Dump expanded type strings used for symbol versions\n"
 	      "  -T, --symtypes file  Write a symtypes file\n"
 	      "  -h, --help           Print this message\n"
 	      "\n",
@@ -69,9 +72,10 @@ static int process_module(Dwfl_Module *mod, void **userdata, const char *name,
 	} while (cu);
 
 	/*
-	 * Use die_map to expand type strings and write them to `symfile`.
+	 * Use die_map to expand type strings, write them to `symfile`, and
+	 * calculate symbol versions.
 	 */
-	generate_symtypes(symfile);
+	generate_symtypes_and_versions(symfile);
 	die_map_free();
 
 	return DWARF_CB_OK;
@@ -92,6 +96,7 @@ int main(int argc, char **argv)
 				 { "dump-dies", 0, &dump_dies, 1 },
 				 { "dump-die-map", 0, &dump_die_map, 1 },
 				 { "dump-types", 0, &dump_types, 1 },
+				 { "dump-versions", 0, &dump_versions, 1 },
 				 { "symtypes", 1, NULL, 'T' },
 				 { "help", 0, NULL, 'h' },
 				 { 0, 0, NULL, 0 } };
@@ -164,6 +169,7 @@ int main(int argc, char **argv)
 	if (symfile)
 		check(fclose(symfile));
 
+	symbol_print_versions();
 	symbol_free();
 
 	return 0;
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 98d5b2315f21..203534abcd35 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -23,6 +23,7 @@ extern int debug;
 extern int dump_dies;
 extern int dump_die_map;
 extern int dump_types;
+extern int dump_versions;
 extern int symtypes;
 
 /*
@@ -95,6 +96,7 @@ static inline unsigned int addr_hash(uintptr_t addr)
 enum symbol_state {
 	SYMBOL_UNPROCESSED,
 	SYMBOL_MAPPED,
+	SYMBOL_PROCESSED
 };
 
 struct symbol_addr {
@@ -109,6 +111,7 @@ struct symbol {
 	struct hlist_node name_hash;
 	enum symbol_state state;
 	uintptr_t die_addr;
+	unsigned long crc;
 };
 
 typedef void (*symbol_callback_t)(struct symbol *, void *arg);
@@ -116,6 +119,10 @@ typedef void (*symbol_callback_t)(struct symbol *, void *arg);
 void symbol_read_exports(FILE *file);
 void symbol_read_symtab(int fd);
 struct symbol *symbol_get(const char *name);
+void symbol_set_die(struct symbol *sym, Dwarf_Die *die);
+void symbol_set_crc(struct symbol *sym, unsigned long crc);
+void symbol_for_each(symbol_callback_t func, void *arg);
+void symbol_print_versions(void);
 void symbol_free(void);
 
 /*
@@ -126,7 +133,8 @@ enum die_state {
 	DIE_INCOMPLETE,
 	DIE_UNEXPANDED,
 	DIE_COMPLETE,
-	DIE_LAST = DIE_COMPLETE
+	DIE_SYMBOL,
+	DIE_LAST = DIE_SYMBOL
 };
 
 enum die_fragment_type {
@@ -156,6 +164,7 @@ static inline const char *die_state_name(enum die_state state)
 	CASE_CONST_TO_STR(DIE_INCOMPLETE)
 	CASE_CONST_TO_STR(DIE_UNEXPANDED)
 	CASE_CONST_TO_STR(DIE_COMPLETE)
+	CASE_CONST_TO_STR(DIE_SYMBOL)
 	}
 
 	error("unexpected die_state: %d", state);
@@ -252,6 +261,6 @@ void process_cu(Dwarf_Die *cudie);
  * types.c
  */
 
-void generate_symtypes(FILE *file);
+void generate_symtypes_and_versions(FILE *file);
 
 #endif /* __GENDWARFKSYMS_H */
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
index 0d2ce7284a53..4c499ba6c86d 100644
--- a/scripts/gendwarfksyms/symbols.c
+++ b/scripts/gendwarfksyms/symbols.c
@@ -66,6 +66,36 @@ static unsigned int for_each(const char *name, symbol_callback_t func,
 	return 0;
 }
 
+static void set_crc(struct symbol *sym, void *data)
+{
+	unsigned long *crc = data;
+
+	if (sym->state == SYMBOL_PROCESSED && sym->crc != *crc)
+		warn("overriding version for symbol %s (crc %lx vs. %lx)",
+		     sym->name, sym->crc, *crc);
+
+	sym->state = SYMBOL_PROCESSED;
+	sym->crc = *crc;
+}
+
+void symbol_set_crc(struct symbol *sym, unsigned long crc)
+{
+	if (for_each(sym->name, set_crc, &crc) == 0)
+		error("no matching symbols: '%s'", sym->name);
+}
+
+static void set_die(struct symbol *sym, void *data)
+{
+	sym->die_addr = (uintptr_t)((Dwarf_Die *)data)->addr;
+	sym->state = SYMBOL_MAPPED;
+}
+
+void symbol_set_die(struct symbol *sym, Dwarf_Die *die)
+{
+	if (for_each(sym->name, set_die, die) == 0)
+		error("no matching symbols: '%s'", sym->name);
+}
+
 static bool is_exported(const char *name)
 {
 	return for_each(name, NULL, NULL) > 0;
@@ -120,6 +150,16 @@ struct symbol *symbol_get(const char *name)
 	return sym;
 }
 
+void symbol_for_each(symbol_callback_t func, void *arg)
+{
+	struct hlist_node *tmp;
+	struct symbol *sym;
+
+	hash_for_each_safe(symbol_names, sym, tmp, name_hash) {
+		func(sym, arg);
+	}
+}
+
 typedef void (*elf_symbol_callback_t)(const char *name, GElf_Sym *sym,
 				      Elf32_Word xndx, void *arg);
 
@@ -246,6 +286,19 @@ void symbol_read_symtab(int fd)
 	elf_for_each_global(fd, elf_set_symbol_addr, NULL);
 }
 
+void symbol_print_versions(void)
+{
+	struct hlist_node *tmp;
+	struct symbol *sym;
+
+	hash_for_each_safe(symbol_names, sym, tmp, name_hash) {
+		if (sym->state != SYMBOL_PROCESSED)
+			warn("no information for symbol %s", sym->name);
+
+		printf("#SYMVER %s 0x%08lx\n", sym->name, sym->crc);
+	}
+}
+
 void symbol_free(void)
 {
 	struct hlist_node *tmp;
diff --git a/scripts/gendwarfksyms/types.c b/scripts/gendwarfksyms/types.c
index 21d7a34228eb..6c03265f4d10 100644
--- a/scripts/gendwarfksyms/types.c
+++ b/scripts/gendwarfksyms/types.c
@@ -6,6 +6,7 @@
 #define _GNU_SOURCE
 #include <inttypes.h>
 #include <stdio.h>
+#include <zlib.h>
 
 #include "gendwarfksyms.h"
 
@@ -178,6 +179,33 @@ static void type_map_free(void)
 	hash_init(type_map);
 }
 
+/*
+ * CRC for a type, with an optional fully expanded type string for
+ * debugging.
+ */
+struct version {
+	struct type_expansion type;
+	unsigned long crc;
+};
+
+static void version_init(struct version *version)
+{
+	version->crc = crc32(0, NULL, 0);
+	type_expansion_init(&version->type);
+}
+
+static void version_free(struct version *version)
+{
+	type_expansion_free(&version->type);
+}
+
+static void version_add(struct version *version, const char *s)
+{
+	version->crc = crc32(version->crc, (void *)s, strlen(s));
+	if (dump_versions)
+		type_expansion_append(&version->type, s, NULL);
+}
+
 /*
  * Type reference format: <prefix>#<name>, where prefix:
  * 	s -> structure
@@ -187,6 +215,12 @@ static void type_map_free(void)
  *
  * Names with spaces are additionally wrapped in single quotes.
  */
+static inline bool is_type_prefix(const char *s)
+{
+	return (s[0] == 's' || s[0] == 'u' || s[0] == 'e' || s[0] == 't') &&
+	       s[1] == '#';
+}
+
 static char get_type_prefix(int tag)
 {
 	switch (tag) {
@@ -214,6 +248,8 @@ static char *get_type_name(struct die *cache)
 		warn("found incomplete cache entry: %p", cache);
 		return NULL;
 	}
+	if (cache->state == DIE_SYMBOL)
+		return NULL;
 	if (!cache->fqn || !*cache->fqn)
 		return NULL;
 
@@ -231,6 +267,39 @@ static char *get_type_name(struct die *cache)
 	return name;
 }
 
+static void __calculate_version(struct version *version, struct list_head *list)
+{
+	struct type_list_entry *entry;
+	struct type_expansion *e;
+
+	/* Calculate a CRC over an expanded type string */
+	list_for_each_entry(entry, list, list) {
+		if (is_type_prefix(entry->str)) {
+			check(type_map_get(entry->str, &e));
+
+			/*
+			 * It's sufficient to expand each type reference just
+			 * once to detect changes.
+			 */
+			if (cache_was_expanded(&expansion_cache, e)) {
+				version_add(version, entry->str);
+			} else {
+				cache_mark_expanded(&expansion_cache, e);
+				__calculate_version(version, &e->expanded);
+			}
+		} else {
+			version_add(version, entry->str);
+		}
+	}
+}
+
+static void calculate_version(struct version *version, struct list_head *list)
+{
+	version_init(version);
+	__calculate_version(version, list);
+	cache_free(&expansion_cache);
+}
+
 static void __type_expand(struct die *cache, struct type_expansion *type,
 			  bool recursive);
 
@@ -337,7 +406,49 @@ static void expand_type(struct die *cache, void *arg)
 	free(name);
 }
 
-void generate_symtypes(FILE *file)
+static void expand_symbol(struct symbol *sym, void *arg)
+{
+	struct type_expansion type;
+	struct version version;
+	struct die *cache;
+
+	/*
+	 * No need to expand again unless we want a symtypes file entry
+	 * for the symbol. Note that this means `sym` has the same address
+	 * as another symbol that was already processed.
+	 */
+	if (!symtypes && sym->state == SYMBOL_PROCESSED)
+		return;
+
+	if (__die_map_get(sym->die_addr, DIE_SYMBOL, &cache))
+		return; /* We'll warn about missing CRCs later. */
+
+	type_expand(cache, &type, false);
+
+	/* If the symbol already has a version, don't calculate it again. */
+	if (sym->state != SYMBOL_PROCESSED) {
+		calculate_version(&version, &type.expanded);
+		symbol_set_crc(sym, version.crc);
+		debug("%s = %lx", sym->name, version.crc);
+
+		if (dump_versions) {
+			checkp(fputs(sym->name, stderr));
+			checkp(fputs(" ", stderr));
+			type_list_write(&version.type.expanded, stderr);
+			checkp(fputs("\n", stderr));
+		}
+
+		version_free(&version);
+	}
+
+	/* These aren't needed in type_map unless we want a symtypes file. */
+	if (symtypes)
+		type_map_add(sym->name, &type);
+
+	type_expansion_free(&type);
+}
+
+void generate_symtypes_and_versions(FILE *file)
 {
 	cache_init(&expansion_cache);
 
@@ -355,7 +466,14 @@ void generate_symtypes(FILE *file)
 	die_map_for_each(expand_type, NULL);
 
 	/*
-	 *   2. If a symtypes file is requested, write type_map contents to
+	 *   2. For each exported symbol, expand the die_map type, and use
+	 *      type_map expansions to calculate a symbol version from the
+	 *      fully expanded type string.
+	 */
+	symbol_for_each(expand_symbol, NULL);
+
+	/*
+	 *   3. If a symtypes file is requested, write type_map contents to
 	 *      the file.
 	 */
 	type_map_write(file);
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 13/18] gendwarfksyms: Add support for kABI rules

[Sami Tolvanen]

Distributions that want to maintain a stable kABI need the ability
to make ABI compatible changes to kernel without affecting symbol
versions, either because of LTS updates or backports.

With genksyms, developers would typically hide these changes from
version calculation with #ifndef __GENKSYMS__, which would result
in the symbol version not changing even though the actual type has
changed.  When we process precompiled object files, this isn't an
option.

To support this use case, add a --stable command line flag that
gates kABI stability features that are not needed in mainline
kernels, but can be useful for distributions, and add support for
kABI rules, which can be used to restrict gendwarfksyms output.

The rules are specified as a set of null-terminated strings stored
in the .discard.gendwarfksyms.kabi_rules section. Each rule consists
of four strings as follows:

  "version\0type\0target\0value"

The version string ensures the structure can be changed in a
backwards compatible way. The type string indicates the type of the
rule, and target and value strings contain rule-specific data.

Initially support two simple rules:

  1. Declaration-only types

     A type declaration can change into a full definition when
     additional includes are pulled in to the TU, which changes the
     versions of any symbol that references the type. Add support
     for defining declaration-only types whose definition is not
     expanded during versioning.

  2. Ignored enumerators

     It's possible to add new enum fields without changing the ABI,
     but as the fields are included in symbol versioning, this would
     change the versions. Add support for ignoring specific fields.

  3. Overridden enumerator values

     Add support for overriding enumerator values when calculating
     versions. This may be needed when the last field of the enum
     is used as a sentinel and new fields must be added before it.

Add examples for using the rules under the examples/ directory.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 scripts/gendwarfksyms/Makefile           |   1 +
 scripts/gendwarfksyms/dwarf.c            |  25 +-
 scripts/gendwarfksyms/examples/kabi.h    |  70 +++++
 scripts/gendwarfksyms/examples/kabi_ex.c |  14 +
 scripts/gendwarfksyms/examples/kabi_ex.h |  64 +++++
 scripts/gendwarfksyms/gendwarfksyms.c    |  11 +-
 scripts/gendwarfksyms/gendwarfksyms.h    |  14 +
 scripts/gendwarfksyms/kabi.c             | 336 +++++++++++++++++++++++
 8 files changed, 531 insertions(+), 4 deletions(-)
 create mode 100644 scripts/gendwarfksyms/examples/kabi.h
 create mode 100644 scripts/gendwarfksyms/examples/kabi_ex.c
 create mode 100644 scripts/gendwarfksyms/examples/kabi_ex.h
 create mode 100644 scripts/gendwarfksyms/kabi.c

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index e889b958957b..6334c7d3c4d5 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -5,6 +5,7 @@ gendwarfksyms-objs += gendwarfksyms.o
 gendwarfksyms-objs += cache.o
 gendwarfksyms-objs += die.o
 gendwarfksyms-objs += dwarf.o
+gendwarfksyms-objs += kabi.o
 gendwarfksyms-objs += symbols.o
 gendwarfksyms-objs += types.o
 
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index bdf899d60707..17f7e6b9a7ff 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -120,13 +120,16 @@ static bool is_definition_private(Dwarf_Die *die)
 	return !!res;
 }
 
-static bool is_kabi_definition(Dwarf_Die *die)
+static bool is_kabi_definition(struct die *cache, Dwarf_Die *die)
 {
 	bool value;
 
 	if (get_flag_attr(die, DW_AT_declaration, &value) && value)
 		return false;
 
+	if (kabi_is_declonly(cache->fqn))
+		return false;
+
 	return !is_definition_private(die);
 }
 
@@ -515,9 +518,10 @@ static void __process_structure_type(struct state *state, struct die *cache,
 	process(cache, " {");
 	process_linebreak(cache, 1);
 
-	expand = state->expand.expand && is_kabi_definition(die);
+	expand = state->expand.expand && is_kabi_definition(cache, die);
 
 	if (expand) {
+		state->expand.current_fqn = cache->fqn;
 		check(process_die_container(state, cache, die, process_func,
 					    match_func));
 	}
@@ -548,13 +552,26 @@ DEFINE_PROCESS_STRUCTURE_TYPE(union)
 static void process_enumerator_type(struct state *state, struct die *cache,
 				    Dwarf_Die *die)
 {
+	bool overridden = false;
 	Dwarf_Word value;
 
+	if (stable) {
+		/* Get the fqn before we process anything */
+		update_fqn(cache, die);
+
+		if (kabi_is_enumerator_ignored(state->expand.current_fqn,
+					       cache->fqn))
+			return;
+
+		overridden = kabi_get_enumerator_value(
+			state->expand.current_fqn, cache->fqn, &value);
+	}
+
 	process_list_comma(state, cache);
 	process(cache, "enumerator");
 	process_fqn(cache, die);
 
-	if (get_udata_attr(die, DW_AT_const_value, &value)) {
+	if (overridden || get_udata_attr(die, DW_AT_const_value, &value)) {
 		process(cache, " = ");
 		process_fmt(cache, "%" PRIu64, value);
 	}
@@ -620,6 +637,7 @@ static void process_cached(struct state *state, struct die *cache,
 static void state_init(struct state *state)
 {
 	state->expand.expand = true;
+	state->expand.current_fqn = NULL;
 	cache_init(&state->expansion_cache);
 }
 
@@ -627,6 +645,7 @@ static void expansion_state_restore(struct expansion_state *state,
 				    struct expansion_state *saved)
 {
 	state->expand = saved->expand;
+	state->current_fqn = saved->current_fqn;
 }
 
 static void expansion_state_save(struct expansion_state *state,
diff --git a/scripts/gendwarfksyms/examples/kabi.h b/scripts/gendwarfksyms/examples/kabi.h
new file mode 100644
index 000000000000..fcd0300e5b58
--- /dev/null
+++ b/scripts/gendwarfksyms/examples/kabi.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 Google LLC
+ *
+ * Example macros for maintaining kABI stability.
+ *
+ * This file is based on android_kabi.h, which has the following notice:
+ *
+ * Heavily influenced by rh_kabi.h which came from the RHEL/CENTOS kernel
+ * and was:
+ *	Copyright (c) 2014 Don Zickus
+ *	Copyright (c) 2015-2018 Jiri Benc
+ *	Copyright (c) 2015 Sabrina Dubroca, Hannes Frederic Sowa
+ *	Copyright (c) 2016-2018 Prarit Bhargava
+ *	Copyright (c) 2017 Paolo Abeni, Larry Woodman
+ */
+
+#ifndef __KABI_H__
+#define __KABI_H__
+
+/* Kernel macros for userspace testing. */
+#ifndef __aligned
+#define __aligned(x) __attribute__((__aligned__(x)))
+#endif
+#ifndef __used
+#define __used __attribute__((__used__))
+#endif
+#ifndef __section
+#define __section(section) __attribute__((__section__(section)))
+#endif
+#ifndef __PASTE
+#define ___PASTE(a, b) a##b
+#define __PASTE(a, b) ___PASTE(a, b)
+#endif
+#ifndef __stringify
+#define __stringify_1(x...) #x
+#define __stringify(x...) __stringify_1(x)
+#endif
+
+#define __KABI_RULE(hint, target, value)                             \
+	static const char __PASTE(__gendwarfksyms_rule_,             \
+				  __COUNTER__)[] __used __aligned(1) \
+		__section(".discard.gendwarfksyms.kabi_rules") =     \
+			"1\0" #hint "\0" #target "\0" #value
+
+/*
+ * KABI_DECLONLY(fqn)
+ *   Treat the struct/union/enum fqn as a declaration, i.e. even if
+ *   a definition is available, don't expand the contents.
+ */
+#define KABI_DECLONLY(fqn) __KABI_RULE(declonly, fqn, )
+
+/*
+ * KABI_ENUMERATOR_IGNORE(fqn, field)
+ *   When expanding enum fqn, skip the provided field. This makes it
+ *   possible to hide added enum fields from versioning.
+ */
+#define KABI_ENUMERATOR_IGNORE(fqn, field) \
+	__KABI_RULE(enumerator_ignore, fqn field, )
+
+/*
+ * KABI_ENUMERATOR_VALUE(fqn, field, value)
+ *   When expanding enum fqn, use the provided value for the
+ *   specified field. This makes it possible to override enumerator
+ *   values when calculating versions.
+ */
+#define KABI_ENUMERATOR_VALUE(fqn, field, value) \
+	__KABI_RULE(enumerator_value, fqn field, value)
+
+#endif /* __KABI_H__ */
diff --git a/scripts/gendwarfksyms/examples/kabi_ex.c b/scripts/gendwarfksyms/examples/kabi_ex.c
new file mode 100644
index 000000000000..799552ea6679
--- /dev/null
+++ b/scripts/gendwarfksyms/examples/kabi_ex.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * kabi_ex.c
+ *
+ * Copyright (C) 2024 Google LLC
+ *
+ * Examples for kABI stability features with --stable. See kabi_ex.h
+ * for details.
+ */
+
+#include "kabi_ex.h"
+
+struct s e0;
+enum e e1;
diff --git a/scripts/gendwarfksyms/examples/kabi_ex.h b/scripts/gendwarfksyms/examples/kabi_ex.h
new file mode 100644
index 000000000000..fca1e07c78e2
--- /dev/null
+++ b/scripts/gendwarfksyms/examples/kabi_ex.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * kabi_ex.h
+ *
+ * Copyright (C) 2024 Google LLC
+ *
+ * Examples for kABI stability features with --stable.
+ */
+
+/*
+ * The comments below each example contain the expected gendwarfksyms
+ * output, which can be verified using LLVM's FileCheck tool:
+ *
+ * https://llvm.org/docs/CommandGuide/FileCheck.html
+ *
+ * Usage:
+ *
+ * $ gcc -g -c examples/kabi_ex.c -o examples/kabi_ex.o
+ *
+ * $ nm examples/kabi_ex.o | awk '{ print $NF }' | \
+ * 	./gendwarfksyms --stable --dump-dies \
+ * 		examples/kabi_ex.o 2>&1 >/dev/null | \
+ * 	FileCheck examples/kabi_ex.h --check-prefix=STABLE
+ */
+
+#ifndef __KABI_EX_H__
+#define __KABI_EX_H__
+
+#include "kabi.h"
+
+/*
+ * Example: kABI rules
+ */
+
+struct s {
+	int a;
+};
+
+KABI_DECLONLY(s);
+
+/*
+ * STABLE:      variable structure_type s {
+ * STABLE-NEXT: }
+ */
+
+enum e {
+	A,
+	B,
+	C,
+	D,
+};
+
+KABI_ENUMERATOR_IGNORE(e, B);
+KABI_ENUMERATOR_IGNORE(e, C);
+KABI_ENUMERATOR_VALUE(e, D, 123456789);
+
+/*
+ * STABLE:      variable enumeration_type e {
+ * STABLE-NEXT:   enumerator A = 0 ,
+ * STABLE-NEXT:   enumerator D = 123456789
+ * STABLE-NEXT: } byte_size(4)
+ */
+
+#endif /* __KABI_EX_H__ */
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index fd2429ea198f..25865d9eab56 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -25,6 +25,8 @@ int dump_die_map;
 int dump_types;
 /* Print out expanded type strings used for symbol versions */
 int dump_versions;
+/* Support kABI stability features */
+int stable;
 /* Write a symtypes file */
 int symtypes;
 static const char *symtypes_file;
@@ -38,6 +40,7 @@ static void usage(void)
 	      "      --dump-die-map   Print debugging information about die_map changes\n"
 	      "      --dump-types     Dump type strings\n"
 	      "      --dump-versions  Dump expanded type strings used for symbol versions\n"
+	      "  -s, --stable         Support kABI stability features\n"
 	      "  -T, --symtypes file  Write a symtypes file\n"
 	      "  -h, --help           Print this message\n"
 	      "\n",
@@ -97,17 +100,21 @@ int main(int argc, char **argv)
 				 { "dump-die-map", 0, &dump_die_map, 1 },
 				 { "dump-types", 0, &dump_types, 1 },
 				 { "dump-versions", 0, &dump_versions, 1 },
+				 { "stable", 0, NULL, 's' },
 				 { "symtypes", 1, NULL, 'T' },
 				 { "help", 0, NULL, 'h' },
 				 { 0, 0, NULL, 0 } };
 
-	while ((opt = getopt_long(argc, argv, "dT:h", opts, NULL)) != EOF) {
+	while ((opt = getopt_long(argc, argv, "dsT:h", opts, NULL)) != EOF) {
 		switch (opt) {
 		case 0:
 			break;
 		case 'd':
 			debug = 1;
 			break;
+		case 's':
+			stable = 1;
+			break;
 		case 'T':
 			symtypes = 1;
 			symtypes_file = optarg;
@@ -148,6 +155,7 @@ int main(int argc, char **argv)
 			      strerror(errno));
 
 		symbol_read_symtab(fd);
+		kabi_read_rules(fd);
 
 		dwfl = dwfl_begin(&callbacks);
 		if (!dwfl)
@@ -164,6 +172,7 @@ int main(int argc, char **argv)
 			error("dwfl_getmodules failed for '%s'", argv[n]);
 
 		dwfl_end(dwfl);
+		kabi_free();
 	}
 
 	if (symfile)
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 203534abcd35..c0207ca10e19 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -24,6 +24,7 @@ extern int dump_dies;
 extern int dump_die_map;
 extern int dump_types;
 extern int dump_versions;
+extern int stable;
 extern int symtypes;
 
 /*
@@ -232,6 +233,7 @@ static inline bool cache_was_expanded(struct cache *cache, void *addr)
 
 struct expansion_state {
 	bool expand;
+	const char *current_fqn;
 };
 
 struct state {
@@ -263,4 +265,16 @@ void process_cu(Dwarf_Die *cudie);
 
 void generate_symtypes_and_versions(FILE *file);
 
+/*
+ * kabi.c
+ */
+
+bool kabi_is_enumerator_ignored(const char *fqn, const char *field);
+bool kabi_get_enumerator_value(const char *fqn, const char *field,
+			       unsigned long *value);
+bool kabi_is_declonly(const char *fqn);
+
+void kabi_read_rules(int fd);
+void kabi_free(void);
+
 #endif /* __GENDWARFKSYMS_H */
diff --git a/scripts/gendwarfksyms/kabi.c b/scripts/gendwarfksyms/kabi.c
new file mode 100644
index 000000000000..66f01fcd1607
--- /dev/null
+++ b/scripts/gendwarfksyms/kabi.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#define _GNU_SOURCE
+#include <errno.h>
+#include <stdio.h>
+
+#include "gendwarfksyms.h"
+
+#define KABI_RULE_SECTION ".discard.gendwarfksyms.kabi_rules"
+#define KABI_RULE_VERSION "1"
+
+/*
+ * The rule section consists of four null-terminated strings per
+ * entry:
+ *
+ *   1. version
+ *      Entry format version. Must match KABI_RULE_VERSION.
+ *
+ *   2. type
+ *      Type of the kABI rule. Must be one of the tags defined below.
+ *
+ *   3. target
+ *      Rule-dependent target, typically the fully qualified name of
+ *      the target DIE.
+ *
+ *   4. value
+ *      Rule-dependent value.
+ */
+#define KABI_RULE_MIN_ENTRY_SIZE                                  \
+	(/* version\0 */ 2 + /* type\0 */ 2 + /* target\0" */ 1 + \
+	 /* value\0 */ 1)
+#define KABI_RULE_EMPTY_VALUE ""
+
+/*
+ * Rule: declonly
+ * - For the struct/enum/union in the target field, treat it as a
+ *   declaration only even if a definition is available.
+ */
+#define KABI_RULE_TAG_DECLONLY "declonly"
+
+/*
+ * Rule: enumerator_ignore
+ * - For the enum_field in the target field, ignore the enumerator.
+ */
+#define KABI_RULE_TAG_ENUMERATOR_IGNORE "enumerator_ignore"
+
+/*
+ * Rule: enumerator_value
+ * - For the fqn_field in the target field, set the value to the
+ *   unsigned integer in the value field.
+ */
+#define KABI_RULE_TAG_ENUMERATOR_VALUE "enumerator_value"
+
+enum kabi_rule_type {
+	KABI_RULE_TYPE_UNKNOWN,
+	KABI_RULE_TYPE_DECLONLY,
+	KABI_RULE_TYPE_ENUMERATOR_IGNORE,
+	KABI_RULE_TYPE_ENUMERATOR_VALUE,
+};
+
+#define RULE_HASH_BITS 7
+
+struct rule {
+	enum kabi_rule_type type;
+	const char *target;
+	const char *value;
+	struct hlist_node hash;
+};
+
+/* { type, target } -> struct rule */
+static HASHTABLE_DEFINE(rules, 1 << RULE_HASH_BITS);
+
+static inline unsigned int rule_values_hash(enum kabi_rule_type type,
+					    const char *target)
+{
+	return hash_32(type) ^ hash_str(target);
+}
+
+static inline unsigned int rule_hash(const struct rule *rule)
+{
+	return rule_values_hash(rule->type, rule->target);
+}
+
+static inline const char *get_rule_field(const char **pos, ssize_t *left)
+{
+	const char *start = *pos;
+	size_t len;
+
+	if (*left <= 0)
+		error("unexpected end of kABI rules");
+
+	len = strnlen(start, *left) + 1;
+	*pos += len;
+	*left -= len;
+
+	return start;
+}
+
+void kabi_read_rules(int fd)
+{
+	GElf_Shdr shdr_mem;
+	GElf_Shdr *shdr;
+	Elf_Data *rule_data = NULL;
+	Elf_Scn *scn;
+	Elf *elf;
+	size_t shstrndx;
+	const char *rule_str;
+	ssize_t left;
+	int i;
+
+	const struct {
+		enum kabi_rule_type type;
+		const char *tag;
+	} rule_types[] = {
+		{
+			.type = KABI_RULE_TYPE_DECLONLY,
+			.tag = KABI_RULE_TAG_DECLONLY,
+		},
+		{
+			.type = KABI_RULE_TYPE_ENUMERATOR_IGNORE,
+			.tag = KABI_RULE_TAG_ENUMERATOR_IGNORE,
+		},
+		{
+			.type = KABI_RULE_TYPE_ENUMERATOR_VALUE,
+			.tag = KABI_RULE_TAG_ENUMERATOR_VALUE,
+		},
+	};
+
+	if (!stable)
+		return;
+
+	if (elf_version(EV_CURRENT) != EV_CURRENT)
+		error("elf_version failed: %s", elf_errmsg(-1));
+
+	elf = elf_begin(fd, ELF_C_READ_MMAP, NULL);
+	if (!elf)
+		error("elf_begin failed: %s", elf_errmsg(-1));
+
+	if (elf_getshdrstrndx(elf, &shstrndx) < 0)
+		error("elf_getshdrstrndx failed: %s", elf_errmsg(-1));
+
+	scn = elf_nextscn(elf, NULL);
+
+	while (scn) {
+		const char *sname;
+
+		shdr = gelf_getshdr(scn, &shdr_mem);
+		if (!shdr)
+			error("gelf_getshdr failed: %s", elf_errmsg(-1));
+
+		sname = elf_strptr(elf, shstrndx, shdr->sh_name);
+		if (!sname)
+			error("elf_strptr failed: %s", elf_errmsg(-1));
+
+		if (!strcmp(sname, KABI_RULE_SECTION)) {
+			rule_data = elf_getdata(scn, NULL);
+			if (!rule_data)
+				error("elf_getdata failed: %s", elf_errmsg(-1));
+			break;
+		}
+
+		scn = elf_nextscn(elf, scn);
+	}
+
+	if (!rule_data) {
+		debug("kABI rules not found");
+		check(elf_end(elf));
+		return;
+	}
+
+	rule_str = rule_data->d_buf;
+	left = shdr->sh_size;
+
+	if (left < KABI_RULE_MIN_ENTRY_SIZE)
+		error("kABI rule section too small: %zd bytes", left);
+
+	if (rule_str[left - 1] != '\0')
+		error("kABI rules are not null-terminated");
+
+	while (left > KABI_RULE_MIN_ENTRY_SIZE) {
+		enum kabi_rule_type type = KABI_RULE_TYPE_UNKNOWN;
+		const char *field;
+		struct rule *rule;
+
+		/* version */
+		field = get_rule_field(&rule_str, &left);
+
+		if (strcmp(field, KABI_RULE_VERSION))
+			error("unsupported kABI rule version: '%s'", field);
+
+		/* type */
+		field = get_rule_field(&rule_str, &left);
+
+		for (i = 0; i < ARRAY_SIZE(rule_types); i++) {
+			if (!strcmp(field, rule_types[i].tag)) {
+				type = rule_types[i].type;
+				break;
+			}
+		}
+
+		if (type == KABI_RULE_TYPE_UNKNOWN)
+			error("unsupported kABI rule type: '%s'", field);
+
+		rule = xmalloc(sizeof(struct rule));
+
+		rule->type = type;
+		rule->target = xstrdup(get_rule_field(&rule_str, &left));
+		rule->value = xstrdup(get_rule_field(&rule_str, &left));
+
+		hash_add(rules, &rule->hash, rule_hash(rule));
+
+		debug("kABI rule: type: '%s', target: '%s', value: '%s'", field,
+		      rule->target, rule->value);
+	}
+
+	if (left > 0)
+		warn("unexpected data at the end of the kABI rules section");
+
+	check(elf_end(elf));
+}
+
+bool kabi_is_declonly(const char *fqn)
+{
+	struct rule *rule;
+
+	if (!stable)
+		return false;
+	if (!fqn || !*fqn)
+		return false;
+
+	hash_for_each_possible(rules, rule, hash,
+			       rule_values_hash(KABI_RULE_TYPE_DECLONLY, fqn)) {
+		if (rule->type == KABI_RULE_TYPE_DECLONLY &&
+		    !strcmp(fqn, rule->target))
+			return true;
+	}
+
+	return false;
+}
+
+static char *get_enumerator_target(const char *fqn, const char *field)
+{
+	char *target = NULL;
+
+	if (asprintf(&target, "%s %s", fqn, field) < 0)
+		error("asprintf failed for '%s %s'", fqn, field);
+
+	return target;
+}
+
+static unsigned long get_ulong_value(const char *value)
+{
+	unsigned long result = 0;
+	char *endptr = NULL;
+
+	errno = 0;
+	result = strtoul(value, &endptr, 10);
+
+	if (errno || *endptr)
+		error("invalid unsigned value '%s'", value);
+
+	return result;
+}
+
+bool kabi_is_enumerator_ignored(const char *fqn, const char *field)
+{
+	bool match = false;
+	struct rule *rule;
+	char *target;
+
+	if (!stable)
+		return false;
+	if (!fqn || !*fqn || !field || !*field)
+		return false;
+
+	target = get_enumerator_target(fqn, field);
+
+	hash_for_each_possible(
+		rules, rule, hash,
+		rule_values_hash(KABI_RULE_TYPE_ENUMERATOR_IGNORE, target)) {
+		if (rule->type == KABI_RULE_TYPE_ENUMERATOR_IGNORE &&
+		    !strcmp(target, rule->target)) {
+			match = true;
+			break;
+		}
+	}
+
+	free(target);
+	return match;
+}
+
+bool kabi_get_enumerator_value(const char *fqn, const char *field,
+			       unsigned long *value)
+{
+	bool match = false;
+	struct rule *rule;
+	char *target;
+
+	if (!stable)
+		return false;
+	if (!fqn || !*fqn || !field || !*field)
+		return false;
+
+	target = get_enumerator_target(fqn, field);
+
+	hash_for_each_possible(rules, rule, hash,
+			       rule_values_hash(KABI_RULE_TYPE_ENUMERATOR_VALUE,
+						target)) {
+		if (rule->type == KABI_RULE_TYPE_ENUMERATOR_VALUE &&
+		    !strcmp(target, rule->target)) {
+			*value = get_ulong_value(rule->value);
+			match = true;
+			break;
+		}
+	}
+
+	free(target);
+	return match;
+}
+
+void kabi_free(void)
+{
+	struct hlist_node *tmp;
+	struct rule *rule;
+
+	hash_for_each_safe(rules, rule, tmp, hash) {
+		free((void *)rule->target);
+		free((void *)rule->value);
+		free(rule);
+	}
+
+	hash_init(rules);
+}
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 14/18] gendwarfksyms: Add support for reserved and ignored fields

[Sami Tolvanen]

Distributions that want to maintain a stable kABI need the ability
to make ABI compatible changes to kernel data structures without
affecting symbol versions, either because of LTS updates or backports.

With genksyms, developers would typically hide these changes from
version calculation with #ifndef __GENKSYMS__, which would result
in the symbol version not changing even though the actual type has
changed.  When we process precompiled object files, this isn't an
option.

Change union processing to recognize field name prefixes that allow
the user to ignore the union completely during symbol versioning with
a __kabi_ignored prefix in a field name, or to replace the type of a
placeholder field using a __kabi_reserved field name prefix.

For example, assume we want to add a new field to an existing
alignment hole in a data structure, and ignore the new field when
calculating symbol versions:

  struct struct1 {
    int a;
    /* a 4-byte alignment hole */
    unsigned long b;
  };

To add `int n` to the alignment hole, we can add a union that includes
a __kabi_ignored field that causes gendwarfksyms to ignore the entire
union:

  struct struct1 {
    int a;
    union {
      char __kabi_ignored_0;
      int n;
    };
    unsigned long b;
  };

With --stable, both structs produce the same symbol version.

Alternatively, when a distribution expects future modification to a
data structure, they can explicitly add reserved fields:

  struct struct2 {
    long a;
    long __kabi_reserved_0; /* reserved for future use */
  };

To take the field into use, we can again replace it with a union, with
one of the fields keeping the __kabi_reserved name prefix to indicate
the original type:

  struct struct2 {
    long a;
    union {
      long __kabi_reserved_0;
      struct {
          int b;
          int v;
      };
    };

Here gendwarfksyms --stable replaces the union with the type of the
placeholder field when calculating versions.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c            | 248 ++++++++++++++++++++++-
 scripts/gendwarfksyms/examples/kabi.h    |  87 ++++++++
 scripts/gendwarfksyms/examples/kabi_ex.c |  16 ++
 scripts/gendwarfksyms/examples/kabi_ex.h | 199 ++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.h    |   9 +
 5 files changed, 558 insertions(+), 1 deletion(-)

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 17f7e6b9a7ff..746a89d9e3d4 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -3,10 +3,33 @@
  * Copyright (C) 2024 Google LLC
  */
 
+#include <assert.h>
 #include <inttypes.h>
 #include <stdarg.h>
 #include "gendwarfksyms.h"
 
+/* See get_union_kabi_status */
+#define KABI_PREFIX "__kabi_"
+#define KABI_PREFIX_LEN (sizeof(KABI_PREFIX) - 1)
+#define KABI_RESERVED_PREFIX "reserved"
+#define KABI_RESERVED_PREFIX_LEN (sizeof(KABI_RESERVED_PREFIX) - 1)
+#define KABI_RENAMED_PREFIX "renamed"
+#define KABI_RENAMED_PREFIX_LEN (sizeof(KABI_RENAMED_PREFIX) - 1)
+#define KABI_IGNORED_PREFIX "ignored"
+#define KABI_IGNORED_PREFIX_LEN (sizeof(KABI_IGNORED_PREFIX) - 1)
+
+static inline bool is_kabi_prefix(const char *name)
+{
+	return name && !strncmp(name, KABI_PREFIX, KABI_PREFIX_LEN);
+}
+
+enum kabi_status {
+	/* >0 to stop DIE processing */
+	KABI_NORMAL = 1,
+	KABI_RESERVED,
+	KABI_IGNORED,
+};
+
 static bool do_linebreak;
 static int indentation_level;
 
@@ -353,13 +376,23 @@ static void __process_list_type(struct state *state, struct die *cache,
 {
 	const char *name = get_name_attr(die);
 
+	if (stable) {
+		if (is_kabi_prefix(name))
+			name = NULL;
+		state->kabi.orig_name = NULL;
+	}
+
 	process_list_comma(state, cache);
 	process(cache, type);
 	process_type_attr(state, cache, die);
+
+	if (stable && state->kabi.orig_name)
+		name = state->kabi.orig_name;
 	if (name) {
 		process(cache, " ");
 		process(cache, name);
 	}
+
 	process_accessibility_attr(cache, die);
 	process_bit_size_attr(cache, die);
 	process_data_bit_offset_attr(cache, die);
@@ -486,11 +519,208 @@ static void process_variant_part_type(struct state *state, struct die *cache,
 	process(cache, "}");
 }
 
+static int get_kabi_status(Dwarf_Die *die, const char **suffix)
+{
+	const char *name = get_name_attr(die);
+
+	if (suffix)
+		*suffix = NULL;
+
+	if (is_kabi_prefix(name)) {
+		name += KABI_PREFIX_LEN;
+
+		if (!strncmp(name, KABI_RESERVED_PREFIX,
+			     KABI_RESERVED_PREFIX_LEN))
+			return KABI_RESERVED;
+		if (!strncmp(name, KABI_IGNORED_PREFIX,
+			     KABI_IGNORED_PREFIX_LEN))
+			return KABI_IGNORED;
+
+		if (!strncmp(name, KABI_RENAMED_PREFIX,
+			     KABI_RENAMED_PREFIX_LEN)) {
+			if (suffix) {
+				name += KABI_RENAMED_PREFIX_LEN;
+				*suffix = name;
+			}
+			return KABI_RESERVED;
+		}
+	}
+
+	return KABI_NORMAL;
+}
+
+static int check_struct_member_kabi_status(struct state *state,
+					   struct die *__unused, Dwarf_Die *die)
+{
+	int res;
+
+	assert(dwarf_tag(die) == DW_TAG_member_type);
+
+	/*
+	 * If the union member is a struct, expect the __kabi field to
+	 * be the first member of the structure, i.e..:
+	 *
+	 * union {
+	 * 	type new_member;
+	 * 	struct {
+	 * 		type __kabi_field;
+	 * 	}
+	 * };
+	 */
+	res = get_kabi_status(die, &state->kabi.orig_name);
+
+	if (res == KABI_RESERVED &&
+	    !get_ref_die_attr(die, DW_AT_type, &state->kabi.placeholder))
+		error("structure member missing a type?");
+
+	return res;
+}
+
+static int check_union_member_kabi_status(struct state *state,
+					  struct die *__unused, Dwarf_Die *die)
+{
+	Dwarf_Die type;
+	int res;
+
+	assert(dwarf_tag(die) == DW_TAG_member_type);
+
+	if (!get_ref_die_attr(die, DW_AT_type, &type))
+		error("union member missing a type?");
+
+	/*
+	 * We expect a union with two members. Check if either of them
+	 * has a __kabi name prefix, i.e.:
+	 *
+	 * union {
+	 * 	...
+	 * 	type memberN; // <- type, N = {0,1}
+	 *	...
+	 * };
+	 *
+	 * The member can also be a structure type, in which case we'll
+	 * check the first structure member.
+	 *
+	 * In any case, stop processing after we've seen two members.
+	 */
+	res = get_kabi_status(die, &state->kabi.orig_name);
+
+	if (res == KABI_RESERVED)
+		state->kabi.placeholder = type;
+	if (res != KABI_NORMAL)
+		return res;
+
+	if (dwarf_tag(&type) == DW_TAG_structure_type)
+		res = checkp(process_die_container(
+			state, NULL, &type, check_struct_member_kabi_status,
+			match_member_type));
+
+	if (res <= KABI_NORMAL && ++state->kabi.members < 2)
+		return 0; /* Continue */
+
+	return res;
+}
+
+static int get_union_kabi_status(Dwarf_Die *die, Dwarf_Die *placeholder,
+				 const char **orig_name)
+{
+	struct state state;
+	int res;
+
+	if (!stable)
+		return KABI_NORMAL;
+
+	/*
+	 * To maintain a stable kABI, distributions may choose to reserve
+	 * space in structs for later use by adding placeholder members,
+	 * for example:
+	 *
+	 * struct s {
+	 * 	u32 a;
+	 *	// an 8-byte placeholder for future use
+	 * 	u64 __kabi_reserved_0;
+	 * };
+	 *
+	 * When the reserved member is taken into use, the type change
+	 * would normally cause the symbol version to change as well, but
+	 * if the replacement uses the following convention, gendwarfksyms
+	 * continues to use the placeholder type for versioning instead,
+	 * thus maintaining the same symbol version:
+	 *
+	 * struct s {
+	 * 	u32 a;
+	 *	union {
+	 * 		// placeholder replaced with a new member `b`
+	 * 		struct t b;
+	 * 		struct {
+	 * 			// the placeholder type that is still
+	 *			// used for versioning
+	 * 			u64 __kabi_reserved_0;
+	 * 		};
+	 * 	};
+	 * };
+	 *
+	 * I.e., as long as the replaced member is in a union, and the
+	 * placeholder has a __kabi_reserved name prefix, we'll continue
+	 * to use the placeholder type (here u64) for version calculation
+	 * instead of the union type.
+	 *
+	 * It's also possible to ignore new members from versioning if
+	 * they've been added to alignment holes, for example, by
+	 * including them in a union with another member that uses the
+	 * __kabi_ignored name prefix:
+	 *
+	 * struct s {
+	 * 	u32 a;
+	 *	// an alignment hole is used to add `n`
+	 * 	union {
+	 * 		u32 n;
+	 *		// hide the entire union member from versioning
+	 * 		u8 __kabi_ignored_0;
+	 * 	};
+	 * 	u64 b;
+	 * };
+	 *
+	 * Note that the user of this feature is responsible for ensuring
+	 * that the structure actually remains ABI compatible.
+	 */
+	memset(&state.kabi, 0, sizeof(struct kabi_state));
+
+	res = checkp(process_die_container(&state, NULL, die,
+					   check_union_member_kabi_status,
+					   match_member_type));
+
+	if (res == KABI_RESERVED) {
+		if (placeholder)
+			*placeholder = state.kabi.placeholder;
+		if (orig_name)
+			*orig_name = state.kabi.orig_name;
+	}
+
+	return res;
+}
+
+static bool is_kabi_ignored(Dwarf_Die *die)
+{
+	Dwarf_Die type;
+
+	if (!stable)
+		return false;
+
+	if (!get_ref_die_attr(die, DW_AT_type, &type))
+		error("member missing a type?");
+
+	return dwarf_tag(&type) == DW_TAG_union_type &&
+	       checkp(get_union_kabi_status(&type, NULL, NULL)) == KABI_IGNORED;
+}
+
 static int ___process_structure_type(struct state *state, struct die *cache,
 				     Dwarf_Die *die)
 {
 	switch (dwarf_tag(die)) {
 	case DW_TAG_member:
+		if (is_kabi_ignored(die))
+			return 0;
+		return check(process_type(state, cache, die));
 	case DW_TAG_variant_part:
 		return check(process_type(state, cache, die));
 	case DW_TAG_class_type:
@@ -547,7 +777,23 @@ static void __process_structure_type(struct state *state, struct die *cache,
 
 DEFINE_PROCESS_STRUCTURE_TYPE(class)
 DEFINE_PROCESS_STRUCTURE_TYPE(structure)
-DEFINE_PROCESS_STRUCTURE_TYPE(union)
+
+static void process_union_type(struct state *state, struct die *cache,
+			       Dwarf_Die *die)
+{
+	Dwarf_Die placeholder;
+
+	int res = checkp(get_union_kabi_status(die, &placeholder,
+					       &state->kabi.orig_name));
+
+	if (res == KABI_RESERVED)
+		check(process_type(state, cache, &placeholder));
+	if (res > KABI_NORMAL)
+		return;
+
+	__process_structure_type(state, cache, die, "union_type",
+				 ___process_structure_type, match_all);
+}
 
 static void process_enumerator_type(struct state *state, struct die *cache,
 				    Dwarf_Die *die)
diff --git a/scripts/gendwarfksyms/examples/kabi.h b/scripts/gendwarfksyms/examples/kabi.h
index fcd0300e5b58..97a5669b083d 100644
--- a/scripts/gendwarfksyms/examples/kabi.h
+++ b/scripts/gendwarfksyms/examples/kabi.h
@@ -43,6 +43,28 @@
 		__section(".discard.gendwarfksyms.kabi_rules") =     \
 			"1\0" #hint "\0" #target "\0" #value
 
+#define __KABI_NORMAL_SIZE_ALIGN(_orig, _new)                                             \
+	union {                                                                           \
+		_Static_assert(                                                           \
+			sizeof(struct { _new; }) <= sizeof(struct { _orig; }),            \
+			__FILE__ ":" __stringify(__LINE__) ": " __stringify(              \
+				_new) " is larger than " __stringify(_orig));             \
+		_Static_assert(                                                           \
+			__alignof__(struct { _new; }) <=                                  \
+				__alignof__(struct { _orig; }),                           \
+			__FILE__ ":" __stringify(__LINE__) ": " __stringify(              \
+				_orig) " is not aligned the same as " __stringify(_new)); \
+	}
+
+#define __KABI_REPLACE(_orig, _new)                    \
+	union {                                        \
+		_new;                                  \
+		struct {                               \
+			_orig;                         \
+		};                                     \
+		__KABI_NORMAL_SIZE_ALIGN(_orig, _new); \
+	}
+
 /*
  * KABI_DECLONLY(fqn)
  *   Treat the struct/union/enum fqn as a declaration, i.e. even if
@@ -67,4 +89,69 @@
 #define KABI_ENUMERATOR_VALUE(fqn, field, value) \
 	__KABI_RULE(enumerator_value, fqn field, value)
 
+/*
+ * KABI_RESERVE
+ *   Reserve some "padding" in a structure for use by LTS backports.
+ *   This is normally placed at the end of a structure.
+ *   number: the "number" of the padding variable in the structure.  Start with
+ *   1 and go up.
+ */
+#define KABI_RESERVE(n) unsigned long __kabi_reserved##n
+
+/*
+ * KABI_RESERVE_ARRAY
+ *   Same as _BACKPORT_RESERVE but allocates an array with the specified
+ *   size in bytes.
+ */
+#define KABI_RESERVE_ARRAY(n, s) \
+	unsigned char __aligned(8) __kabi_reserved##n[s]
+
+/*
+ * KABI_IGNORE
+ *   Add a new field that's ignored in versioning.
+ */
+#define KABI_IGNORE(n, _new)                     \
+	union {                                  \
+		_new;                            \
+		unsigned char __kabi_ignored##n; \
+	}
+
+/*
+ * KABI_REPLACE
+ *   Replace a field with a compatible new field.
+ */
+#define KABI_REPLACE(_oldtype, _oldname, _new) \
+	__KABI_REPLACE(_oldtype __kabi_renamed##_oldname, struct { _new; })
+
+/*
+ * KABI_USE(number, _new)
+ *   Use a previous padding entry that was defined with KABI_RESERVE
+ *   number: the previous "number" of the padding variable
+ *   _new: the variable to use now instead of the padding variable
+ */
+#define KABI_USE(number, _new) __KABI_REPLACE(KABI_RESERVE(number), _new)
+
+/*
+ * KABI_USE2(number, _new1, _new2)
+ *   Use a previous padding entry that was defined with KABI_RESERVE for
+ *   two new variables that fit into 64 bits.  This is good for when you do not
+ *   want to "burn" a 64bit padding variable for a smaller variable size if not
+ *   needed.
+ */
+#define KABI_USE2(number, _new1, _new2)        \
+	__KABI_REPLACE(                        \
+		KABI_RESERVE(number), struct { \
+			_new1;                 \
+			_new2;                 \
+		})
+/*
+ * KABI_USE_ARRAY(number, bytes, _new)
+ *   Use a previous padding entry that was defined with KABI_RESERVE_ARRAY
+ *   number: the previous "number" of the padding variable
+ *   bytes: the size in bytes reserved for the array
+ *   _new: the variable to use now instead of the padding variable
+ */
+#define KABI_USE_ARRAY(number, bytes, _new) \
+	__KABI_REPLACE(KABI_RESERVE_ARRAY(number, bytes), _new)
+
 #endif /* __KABI_H__ */
diff --git a/scripts/gendwarfksyms/examples/kabi_ex.c b/scripts/gendwarfksyms/examples/kabi_ex.c
index 799552ea6679..0b7ffd830541 100644
--- a/scripts/gendwarfksyms/examples/kabi_ex.c
+++ b/scripts/gendwarfksyms/examples/kabi_ex.c
@@ -12,3 +12,19 @@
 
 struct s e0;
 enum e e1;
+
+struct ex0a ex0a;
+struct ex0b ex0b;
+struct ex0c ex0c;
+
+struct ex1a ex1a;
+struct ex1b ex1b;
+struct ex1c ex1c;
+
+struct ex2a ex2a;
+struct ex2b ex2b;
+struct ex2c ex2c;
+
+struct ex3a ex3a;
+struct ex3b ex3b;
+struct ex3c ex3c;
diff --git a/scripts/gendwarfksyms/examples/kabi_ex.h b/scripts/gendwarfksyms/examples/kabi_ex.h
index fca1e07c78e2..1736e0f65208 100644
--- a/scripts/gendwarfksyms/examples/kabi_ex.h
+++ b/scripts/gendwarfksyms/examples/kabi_ex.h
@@ -59,6 +59,205 @@ KABI_ENUMERATOR_VALUE(e, D, 123456789);
  * STABLE-NEXT:   enumerator A = 0 ,
  * STABLE-NEXT:   enumerator D = 123456789
  * STABLE-NEXT: } byte_size(4)
+*/
+
+/*
+ * Example: Reserved fields
+ */
+struct ex0a {
+	int a;
+	KABI_RESERVE(0);
+	KABI_RESERVE(1);
+};
+
+/*
+ * STABLE:      variable structure_type ex0a {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) data_member_location(8) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) data_member_location(16)
+ * STABLE-NEXT: } byte_size(24)
+ */
+
+struct ex0b {
+	int a;
+	KABI_RESERVE(0);
+	KABI_USE2(1, int b, int c);
+};
+
+/*
+ * STABLE:      variable structure_type ex0b {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) data_member_location(8) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) data_member_location(16)
+ * STABLE-NEXT: } byte_size(24)
+ */
+
+struct ex0c {
+	int a;
+	KABI_USE(0, void *p);
+	KABI_USE2(1, int b, int c);
+};
+
+/*
+ * STABLE:      variable structure_type ex0c {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) data_member_location(8) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) data_member_location(16)
+ * STABLE-NEXT: } byte_size(24)
+ */
+
+/*
+ * Example: A reserved array
+ */
+
+struct ex1a {
+	unsigned int a;
+	KABI_RESERVE_ARRAY(0, 64);
+};
+
+/*
+ * STABLE:      variable structure_type ex1a {
+ * STABLE-NEXT:   member base_type unsigned int byte_size(4) encoding(7) a data_member_location(0) ,
+ * STABLE-NEXT:   member array_type[64] {
+ * STABLE-NEXT:     base_type unsigned char byte_size(1) encoding(8)
+ * STABLE-NEXT:   } data_member_location(8)
+ * STABLE-NEXT: } byte_size(72)
+ */
+
+struct ex1b {
+	unsigned int a;
+	KABI_USE_ARRAY(
+		0, 64, struct {
+			void *p;
+			KABI_RESERVE_ARRAY(1, 56);
+		});
+};
+
+/*
+ * STABLE:      variable structure_type ex1b {
+ * STABLE-NEXT:   member base_type unsigned int byte_size(4) encoding(7) a data_member_location(0) ,
+ * STABLE-NEXT:   member array_type[64] {
+ * STABLE-NEXT:     base_type unsigned char byte_size(1) encoding(8)
+ * STABLE-NEXT:   } data_member_location(8)
+ * STABLE-NEXT: } byte_size(72)
+ */
+
+struct ex1c {
+	unsigned int a;
+	KABI_USE_ARRAY(0, 64, void *p[8]);
+};
+
+/*
+ * STABLE:      variable structure_type ex1c {
+ * STABLE-NEXT:   member base_type unsigned int byte_size(4) encoding(7) a data_member_location(0) ,
+ * STABLE-NEXT:   member array_type[64] {
+ * STABLE-NEXT:     base_type unsigned char byte_size(1) encoding(8)
+ * STABLE-NEXT:   } data_member_location(8)
+ * STABLE-NEXT: } byte_size(72)
+ */
+
+/*
+ * Example: An ignored field added to an alignment hole
+ */
+
+struct ex2a {
+	int a;
+	unsigned long b;
+	int c;
+	unsigned long d;
+};
+
+/*
+ * STABLE:      variable structure_type ex2a {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) b data_member_location(8)
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) c data_member_location(16) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) d data_member_location(24)
+ * STABLE-NEXT: } byte_size(32)
+ */
+
+struct ex2b {
+	int a;
+	KABI_IGNORE(0, unsigned int n);
+	unsigned long b;
+	int c;
+	unsigned long d;
+};
+
+_Static_assert(sizeof(struct ex2a) == sizeof(struct ex2b), "ex2a size doesn't match ex2b");
+
+/*
+ * STABLE:      variable structure_type ex2b {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) b data_member_location(8)
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) c data_member_location(16) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) d data_member_location(24)
+ * STABLE-NEXT: } byte_size(32)
+ */
+
+struct ex2c {
+	int a;
+	KABI_IGNORE(0, unsigned int n);
+	unsigned long b;
+	int c;
+	KABI_IGNORE(1, unsigned int m);
+	unsigned long d;
+};
+
+_Static_assert(sizeof(struct ex2a) == sizeof(struct ex2c), "ex2a size doesn't match ex2c");
+
+/*
+ * STABLE:      variable structure_type ex2c {
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) a data_member_location(0) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) b data_member_location(8)
+ * STABLE-NEXT:   member base_type int byte_size(4) encoding(5) c data_member_location(16) ,
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) d data_member_location(24)
+ * STABLE-NEXT: } byte_size(32)
+ */
+
+
+/*
+ * Example: A replaced field
+ */
+
+struct ex3a {
+	unsigned long a;
+	unsigned long unused;
+};
+
+/*
+ * STABLE:      variable structure_type ex3a {
+ * STABLE-NEXT:   member base_type [[ULONG:long unsigned int|unsigned long]] byte_size(8) encoding(7) a data_member_location(0)
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) unused data_member_location(8)
+ * STABLE-NEXT: } byte_size(16)
+ */
+
+struct ex3b {
+	unsigned long a;
+	KABI_REPLACE(unsigned long, unused, unsigned long renamed);
+};
+
+_Static_assert(sizeof(struct ex3a) == sizeof(struct ex3b), "ex3a size doesn't match ex3b");
+
+/*
+ * STABLE:      variable structure_type ex3b {
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) a data_member_location(0)
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) unused data_member_location(8)
+ * STABLE-NEXT: } byte_size(16)
+ */
+
+struct ex3c {
+	unsigned long a;
+	KABI_REPLACE(unsigned long, unused, long replaced);
+};
+
+_Static_assert(sizeof(struct ex3a) == sizeof(struct ex3c), "ex3a size doesn't match ex3c");
+
+/*
+ * STABLE:      variable structure_type ex3c {
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) a data_member_location(0)
+ * STABLE-NEXT:   member base_type [[ULONG]] byte_size(8) encoding(7) unused data_member_location(8)
+ * STABLE-NEXT: } byte_size(16)
  */
 
 #endif /* __KABI_EX_H__ */
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index c0207ca10e19..fe49730fe623 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -236,6 +236,12 @@ struct expansion_state {
 	const char *current_fqn;
 };
 
+struct kabi_state {
+	int members;
+	Dwarf_Die placeholder;
+	const char *orig_name;
+};
+
 struct state {
 	struct symbol *sym;
 	Dwarf_Die die;
@@ -246,6 +252,9 @@ struct state {
 	/* Structure expansion */
 	struct expansion_state expand;
 	struct cache expansion_cache;
+
+	/* Reserved or ignored members */
+	struct kabi_state kabi;
 };
 
 typedef int (*die_callback_t)(struct state *state, struct die *cache,
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 15/18] gendwarfksyms: Add support for symbol type pointers

[Sami Tolvanen]

The compiler may choose not to emit type information in DWARF for
external symbols. Clang, for example, does this for symbols not
defined in the current TU.

To provide a way to work around this issue, add support for
__gendwarfksyms_ptr_<symbol> pointers that force the compiler to emit
the necessary type information in DWARF also for the missing symbols.

Example usage:

  #define GENDWARFKSYMS_PTR(sym) \
      static typeof(sym) *__gendwarfksyms_ptr_##sym __used  \
          __section(".discard.gendwarfksyms") = &sym;

  extern int external_symbol(void);
  GENDWARFKSYMS_PTR(external_symbol);

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
---
 scripts/gendwarfksyms/dwarf.c              | 55 +++++++++++++++++++++-
 scripts/gendwarfksyms/examples/symbolptr.c | 33 +++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.h      |  7 +++
 scripts/gendwarfksyms/symbols.c            | 27 +++++++++++
 4 files changed, 121 insertions(+), 1 deletion(-)
 create mode 100644 scripts/gendwarfksyms/examples/symbolptr.c

diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 746a89d9e3d4..534d9aa7c114 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -1061,6 +1061,31 @@ static void process_variable(struct state *state, Dwarf_Die *die)
 	process_symbol(state, die, __process_variable);
 }
 
+static void save_symbol_ptr(struct state *state)
+{
+	Dwarf_Die ptr_type;
+	Dwarf_Die type;
+
+	if (!get_ref_die_attr(&state->die, DW_AT_type, &ptr_type) ||
+	    dwarf_tag(&ptr_type) != DW_TAG_pointer_type)
+		error("%s must be a pointer type!",
+		      get_symbol_name(&state->die));
+
+	if (!get_ref_die_attr(&ptr_type, DW_AT_type, &type))
+		error("%s pointer missing a type attribute?",
+		      get_symbol_name(&state->die));
+
+	/*
+	 * Save the symbol pointer DIE in case the actual symbol is
+	 * missing from the DWARF. Clang, for example, intentionally
+	 * omits external symbols from the debugging information.
+	 */
+	if (dwarf_tag(&type) == DW_TAG_subroutine_type)
+		symbol_set_ptr(state->sym, &type);
+	else
+		symbol_set_ptr(state->sym, &ptr_type);
+}
+
 static int process_exported_symbols(struct state *unused, struct die *cache,
 				    Dwarf_Die *die)
 {
@@ -1084,7 +1109,9 @@ static int process_exported_symbols(struct state *unused, struct die *cache,
 
 		state_init(&state);
 
-		if (tag == DW_TAG_subprogram)
+		if (is_symbol_ptr(get_symbol_name(&state.die)))
+			save_symbol_ptr(&state);
+		else if (tag == DW_TAG_subprogram)
 			process_subprogram(&state, &state.die);
 		else
 			process_variable(&state, &state.die);
@@ -1097,10 +1124,36 @@ static int process_exported_symbols(struct state *unused, struct die *cache,
 	}
 }
 
+static void process_symbol_ptr(struct symbol *sym, void *arg)
+{
+	struct state state;
+	Dwarf *dwarf = arg;
+
+	if (sym->state != SYMBOL_UNPROCESSED || !sym->ptr_die_addr)
+		return;
+
+	debug("%s", sym->name);
+	state_init(&state);
+	state.sym = sym;
+
+	if (!dwarf_die_addr_die(dwarf, (void *)sym->ptr_die_addr, &state.die))
+		error("dwarf_die_addr_die failed for symbol ptr: '%s'",
+		      sym->name);
+
+	if (dwarf_tag(&state.die) == DW_TAG_subroutine_type)
+		process_subprogram(&state, &state.die);
+	else
+		process_variable(&state, &state.die);
+
+	cache_free(&state.expansion_cache);
+}
+
 void process_cu(Dwarf_Die *cudie)
 {
 	check(process_die_container(NULL, NULL, cudie, process_exported_symbols,
 				    match_all));
 
+	symbol_for_each(process_symbol_ptr, dwarf_cu_getdwarf(cudie->cu));
+
 	cache_free(&srcfile_cache);
 }
diff --git a/scripts/gendwarfksyms/examples/symbolptr.c b/scripts/gendwarfksyms/examples/symbolptr.c
new file mode 100644
index 000000000000..88bc1bd60da8
--- /dev/null
+++ b/scripts/gendwarfksyms/examples/symbolptr.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ *
+ * Example for symbol pointers. When compiled with Clang, gendwarfkyms
+ * uses a symbol pointer for `f`.
+ *
+ * $ clang -g -c examples/symbolptr.c -o examples/symbolptr.o
+ * $ echo -e "f\ng\np" | ./gendwarfksyms -d examples/symbolptr.o
+ */
+
+/* Kernel macros for userspace testing. */
+#ifndef __used
+#define __used __attribute__((__used__))
+#endif
+#ifndef __section
+#define __section(section) __attribute__((__section__(section)))
+#endif
+
+#define __GENDWARFKSYMS_EXPORT(sym)				\
+	static typeof(sym) *__gendwarfksyms_ptr_##sym __used	\
+		__section(".discard.gendwarfksyms") = &sym;
+
+extern void f(unsigned int arg);
+void g(int *arg);
+void g(int *arg) {}
+
+struct s;
+extern struct s *p;
+
+__GENDWARFKSYMS_EXPORT(f);
+__GENDWARFKSYMS_EXPORT(g);
+__GENDWARFKSYMS_EXPORT(p);
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index fe49730fe623..197a1a8123c6 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -89,6 +89,10 @@ extern int symtypes;
  * symbols.c
  */
 
+/* See symbols.c:is_symbol_ptr */
+#define SYMBOL_PTR_PREFIX "__gendwarfksyms_ptr_"
+#define SYMBOL_PTR_PREFIX_LEN (sizeof(SYMBOL_PTR_PREFIX) - 1)
+
 static inline unsigned int addr_hash(uintptr_t addr)
 {
 	return hash_ptr((const void *)addr);
@@ -112,14 +116,17 @@ struct symbol {
 	struct hlist_node name_hash;
 	enum symbol_state state;
 	uintptr_t die_addr;
+	uintptr_t ptr_die_addr;
 	unsigned long crc;
 };
 
 typedef void (*symbol_callback_t)(struct symbol *, void *arg);
 
+bool is_symbol_ptr(const char *name);
 void symbol_read_exports(FILE *file);
 void symbol_read_symtab(int fd);
 struct symbol *symbol_get(const char *name);
+void symbol_set_ptr(struct symbol *sym, Dwarf_Die *ptr);
 void symbol_set_die(struct symbol *sym, Dwarf_Die *die);
 void symbol_set_crc(struct symbol *sym, unsigned long crc);
 void symbol_for_each(symbol_callback_t func, void *arg);
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
index 4c499ba6c86d..327f87389c34 100644
--- a/scripts/gendwarfksyms/symbols.c
+++ b/scripts/gendwarfksyms/symbols.c
@@ -39,6 +39,20 @@ static unsigned int __for_each_addr(struct symbol *sym, symbol_callback_t func,
 	return processed;
 }
 
+/*
+ * For symbols without debugging information (e.g. symbols defined in other
+ * TUs), we also match __gendwarfksyms_ptr_<symbol_name> symbols, which the
+ * kernel uses to ensure type information is present in the TU that exports
+ * the symbol. A __gendwarfksyms_ptr pointer must have the same type as the
+ * exported symbol, e.g.:
+ *
+ *   typeof(symname) *__gendwarf_ptr_symname = &symname;
+ */
+bool is_symbol_ptr(const char *name)
+{
+	return name && !strncmp(name, SYMBOL_PTR_PREFIX, SYMBOL_PTR_PREFIX_LEN);
+}
+
 static unsigned int for_each(const char *name, symbol_callback_t func,
 			     void *data)
 {
@@ -47,6 +61,8 @@ static unsigned int for_each(const char *name, symbol_callback_t func,
 
 	if (!name || !*name)
 		return 0;
+	if (is_symbol_ptr(name))
+		name += SYMBOL_PTR_PREFIX_LEN;
 
 	hash_for_each_possible_safe(symbol_names, match, tmp, name_hash,
 				    hash_str(name)) {
@@ -84,6 +100,17 @@ void symbol_set_crc(struct symbol *sym, unsigned long crc)
 		error("no matching symbols: '%s'", sym->name);
 }
 
+static void set_ptr(struct symbol *sym, void *data)
+{
+	sym->ptr_die_addr = (uintptr_t)((Dwarf_Die *)data)->addr;
+}
+
+void symbol_set_ptr(struct symbol *sym, Dwarf_Die *ptr)
+{
+	if (for_each(sym->name, set_ptr, ptr) == 0)
+		error("no matching symbols: '%s'", sym->name);
+}
+
 static void set_die(struct symbol *sym, void *data)
 {
 	sym->die_addr = (uintptr_t)((Dwarf_Die *)data)->addr;
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 16/18] export: Add __gendwarfksyms_ptr_ references to exported symbols

[Sami Tolvanen]

With gendwarfksyms, we need each TU where the EXPORT_SYMBOL() macro
is used to also contain DWARF type information for the symbols it
exports.  However, as a TU can also export external symbols and
compilers may choose not to emit debugging information for symbols not
defined in the current TU, the missing types will result in missing
symbol versions. Stand-alone assembly code also doesn't contain type
information for exported symbols, so we need to compile a temporary
object file with asm-prototypes.h instead, and similarly need to
ensure the DWARF in the temporary object file contains the necessary
types.

To always emit type information for external exports, add explicit
__gendwarfksyms_ptr_<symbol> references to them in EXPORT_SYMBOL().
gendwarfksyms will use the type information for __gendwarfksyms_ptr_*
if needed. Discard the pointers from the final binary to avoid further
bloat.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 include/linux/export.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/linux/export.h b/include/linux/export.h
index 2633df4d31e6..a8c23d945634 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -52,9 +52,24 @@
 
 #else
 
+#ifdef CONFIG_GENDWARFKSYMS
+/*
+ * With CONFIG_GENDWARFKSYMS, ensure the compiler emits debugging
+ * information for all exported symbols, including those defined in
+ * different TUs, by adding a __gendwarfksyms_ptr_<symbol> pointer
+ * that's discarded during the final link.
+ */
+#define __GENDWARFKSYMS_EXPORT(sym)				\
+	static typeof(sym) *__gendwarfksyms_ptr_##sym __used	\
+		__section(".discard.gendwarfksyms") = &sym;
+#else
+#define __GENDWARFKSYMS_EXPORT(sym)
+#endif
+
 #define __EXPORT_SYMBOL(sym, license, ns)			\
 	extern typeof(sym) sym;					\
 	__ADDRESSABLE(sym)					\
+	__GENDWARFKSYMS_EXPORT(sym)				\
 	asm(__stringify(___EXPORT_SYMBOL(sym, license, ns)))
 
 #endif
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 17/18] kbuild: Add gendwarfksyms as an alternative to genksyms

[Sami Tolvanen]

When MODVERSIONS is enabled, allow selecting gendwarfksyms as the
implementation, but default to genksyms.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/module/Kconfig  | 22 ++++++++++++++++++++++
 scripts/Makefile       |  2 +-
 scripts/Makefile.build | 35 +++++++++++++++++++++++++++++------
 3 files changed, 52 insertions(+), 7 deletions(-)

diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 4637f063d0fc..d443fc504ffc 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -169,6 +169,22 @@ config MODVERSIONS
 	  make them incompatible with the kernel you are running.  If
 	  unsure, say N.
 
+choice
+	prompt "Module versioning implementation"
+	depends on MODVERSIONS
+	help
+	  Select the tool used to calculate symbol versions for modules.
+
+	  If unsure, select GENKSYMS.
+
+config GENKSYMS
+	bool "genksyms (from source code)"
+	help
+	  Calculate symbol versions from pre-processed source code using
+	  genksyms.
+
+	  If unsure, say Y.
+
 config GENDWARFKSYMS
 	bool "gendwarfksyms (from debugging information)"
 	depends on DEBUG_INFO
@@ -176,6 +192,12 @@ config GENDWARFKSYMS
 	depends on !DEBUG_INFO_REDUCED && !DEBUG_INFO_SPLIT
 	# Requires ELF object files.
 	depends on !LTO
+	help
+	  Calculate symbol versions from DWARF debugging information using
+	  gendwarfksyms. Requires DEBUG_INFO to be enabled.
+
+	  If unsure, say N.
+endchoice
 
 config ASM_MODVERSIONS
 	bool
diff --git a/scripts/Makefile b/scripts/Makefile
index d7fec46d38c0..8533f4498885 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -53,7 +53,7 @@ hostprogs += unifdef
 targets += module.lds
 
 subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
-subdir-$(CONFIG_MODVERSIONS) += genksyms
+subdir-$(CONFIG_GENKSYMS) += genksyms
 subdir-$(CONFIG_GENDWARFKSYMS) += gendwarfksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_SECURITY_IPE) += ipe
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index c16e4cf54d77..81d9dacad03c 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -107,13 +107,24 @@ cmd_cpp_i_c       = $(CPP) $(c_flags) -o $@ $<
 $(obj)/%.i: $(obj)/%.c FORCE
 	$(call if_changed_dep,cpp_i_c)
 
+getexportsymbols = $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/$(1)/p'
+
+gendwarfksyms = $(objtree)/scripts/gendwarfksyms/gendwarfksyms	\
+	$(if $(KBUILD_SYMTYPES), --symtypes $(@:.o=.symtypes))	\
+	$(if $(KBUILD_GENDWARFKSYMS_STABLE), --stable)
+
 genksyms = $(objtree)/scripts/genksyms/genksyms		\
 	$(if $(KBUILD_SYMTYPES), -T $(@:.o=.symtypes))	\
 	$(if $(KBUILD_PRESERVE), -p)			\
 	$(addprefix -r , $(wildcard $(@:.o=.symref)))
 
 # These mirror gensymtypes_S and co below, keep them in synch.
+ifdef CONFIG_GENDWARFKSYMS
+cmd_gensymtypes_c = $(if $(skip_gendwarfksyms),,	\
+	$(call getexportsymbols,\1) | $(gendwarfksyms) $@)
+else
 cmd_gensymtypes_c = $(CPP) -D__GENKSYMS__ $(c_flags) $< | $(genksyms)
+endif # CONFIG_GENDWARFKSYMS
 
 # LLVM assembly
 # Generate .ll files from .c
@@ -286,14 +297,26 @@ $(obj)/%.rs: $(obj)/%.rs.S FORCE
 # This is convoluted. The .S file must first be preprocessed to run guards and
 # expand names, then the resulting exports must be constructed into plain
 # EXPORT_SYMBOL(symbol); to build our dummy C file, and that gets preprocessed
-# to make the genksyms input.
+# to make the genksyms input or compiled into an object for gendwarfksyms.
 #
 # These mirror gensymtypes_c and co above, keep them in synch.
-cmd_gensymtypes_S =                                                         \
-   { echo "\#include <linux/kernel.h>" ;                                    \
-     echo "\#include <asm/asm-prototypes.h>" ;                              \
-     $(NM) $@ | sed -n 's/.* __export_symbol_\(.*\)/EXPORT_SYMBOL(\1);/p' ; } | \
-    $(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+getasmexports =								\
+   { echo "\#include <linux/kernel.h>" ;				\
+     echo "\#include <linux/string.h>" ;				\
+     echo "\#include <asm/asm-prototypes.h>" ;				\
+     $(call getexportsymbols,EXPORT_SYMBOL(\1);) ; }
+
+ifdef CONFIG_GENDWARFKSYMS
+cmd_gensymtypes_S =							\
+	$(getasmexports) |						\
+	$(CC) $(c_flags) -c -o $(@:.o=.gendwarfksyms.o) -xc -;		\
+	$(call getexportsymbols,\1) |					\
+	$(gendwarfksyms) $(@:.o=.gendwarfksyms.o)
+else
+cmd_gensymtypes_S =							\
+	$(getasmexports) |						\
+	$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)
+endif # CONFIG_GENDWARFKSYMS
 
 quiet_cmd_cpp_s_S = CPP $(quiet_modtag) $@
 cmd_cpp_s_S       = $(CPP) $(a_flags) -o $@ $<
-- 
2.47.1.613.gc27f4b7a9f-goog

[PATCH v7 18/18] Documentation/kbuild: Add DWARF module versioning

[Sami Tolvanen]

Add documentation for gendwarfksyms changes, and the kABI stability
features that can be useful for distributions even though they're not
used in mainline kernels.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 Documentation/kbuild/gendwarfksyms.rst | 308 +++++++++++++++++++++++++
 Documentation/kbuild/index.rst         |   1 +
 2 files changed, 309 insertions(+)
 create mode 100644 Documentation/kbuild/gendwarfksyms.rst

diff --git a/Documentation/kbuild/gendwarfksyms.rst b/Documentation/kbuild/gendwarfksyms.rst
new file mode 100644
index 000000000000..e4beaae7e456
--- /dev/null
+++ b/Documentation/kbuild/gendwarfksyms.rst
@@ -0,0 +1,308 @@
+=======================
+DWARF module versioning
+=======================
+
+1. Introduction
+===============
+
+When CONFIG_MODVERSIONS is enabled, symbol versions for modules
+are typically calculated from preprocessed source code using the
+**genksyms** tool.  However, this is incompatible with languages such
+as Rust, where the source code has insufficient information about
+the resulting ABI. With CONFIG_GENDWARFKSYMS (and CONFIG_DEBUG_INFO)
+selected, **gendwarfksyms** is used instead to calculate symbol versions
+from the DWARF debugging information, which contains the necessary
+details about the final module ABI.
+
+1.1. Usage
+==========
+
+gendwarfksyms accepts a list of object files on the command line, and a
+list of symbol names (one per line) in standard input::
+
+        Usage: gendwarfksyms [options] elf-object-file ... < symbol-list
+
+        Options:
+          -d, --debug          Print debugging information
+              --dump-dies      Dump DWARF DIE contents
+              --dump-die-map   Print debugging information about die_map changes
+              --dump-types     Dump type strings
+              --dump-versions  Dump expanded type strings used for symbol versions
+          -s, --stable         Support kABI stability features
+          -T, --symtypes file  Write a symtypes file
+          -h, --help           Print this message
+
+
+2. Type information availability
+================================
+
+While symbols are typically exported in the same translation unit (TU)
+where they're defined, it's also perfectly fine for a TU to export
+external symbols. For example, this is done when calculating symbol
+versions for exports in stand-alone assembly code.
+
+To ensure the compiler emits the necessary DWARF type information in the
+TU where symbols are actually exported, gendwarfksyms adds a pointer
+to exported symbols in the `EXPORT_SYMBOL()` macro using the following
+macro::
+
+        #define __GENDWARFKSYMS_EXPORT(sym)                             \
+                static typeof(sym) *__gendwarfksyms_ptr_##sym __used    \
+                        __section(".discard.gendwarfksyms") = &sym;
+
+
+When a symbol pointer is found in DWARF, gendwarfksyms can use its
+type for calculating symbol versions even if the symbol is defined
+elsewhere. The name of the symbol pointer is expected to start with
+`__gendwarfksyms_ptr_`, followed by the name of the exported symbol.
+
+3. Symtypes output format
+=========================
+
+Similarly to genksyms, gendwarfksyms supports writing a symtypes
+file for each processed object that contain types for exported
+symbols and each referenced type that was used in calculating symbol
+versions. These files can be useful when trying to determine what
+exactly caused symbol versions to change between builds. To generate
+symtypes files during a kernel build, set `KBUILD_SYMTYPES=1`.
+
+Matching the existing format, the first column of each line contains
+either a type reference or a symbol name. Type references have a
+one-letter prefix followed by "#" and the name of the type. Four
+reference types are supported::
+
+        e#<type> = enum
+        s#<type> = struct
+        t#<type> = typedef
+        u#<type> = union
+
+Type names with spaces in them are wrapped in single quotes, e.g.::
+
+        s#'core::result::Result<u8, core::num::error::ParseIntError>'
+
+The rest of the line contains a type string. Unlike with genksyms that
+produces C-style type strings, gendwarfksyms uses the same simple parsed
+DWARF format produced by **--dump-dies**, but with type references
+instead of fully expanded strings.
+
+4. Maintaining a stable kABI
+============================
+
+Distribution maintainers often need the ability to make ABI compatible
+changes to kernel data structures due to LTS updates or backports. Using
+the traditional `#ifndef __GENKSYMS__` to hide these changes from symbol
+versioning won't work when processing object files. To support this
+use case, gendwarfksyms provides kABI stability features designed to
+hide changes that won't affect the ABI when calculating versions. These
+features are all gated behind the **--stable** command line flag and are
+not used in the mainline kernel. To use stable features during a kernel
+build, set `KBUILD_GENDWARFKSYMS_STABLE=1`.
+
+Examples for using these features are provided in the
+**scripts/gendwarfksyms/examples** directory, including helper macros
+for source code annotation. Note that as these features are only used to
+transform the inputs for symbol versioning, the user is responsible for
+ensuring that their changes actually won't break the ABI.
+
+4.1. kABI rules
+===============
+
+kABI rules allow distributions to fine-tune certain parts
+of gendwarfksyms output and thus control how symbol
+versions are calculated. These rules are defined in the
+`.discard.gendwarfksyms.kabi_rules` section of the object file and
+consist of simple null-terminated strings with the following structure::
+
+	version\0type\0target\0value\0
+
+This string sequence is repeated as many times as needed to express all
+the rules. The fields are as follows:
+
+- `version`: Ensures backward compatibility for future changes to the
+  structure. Currently expected to be "1".
+- `type`: Indicates the type of rule being applied.
+- `target`: Specifies the target of the rule, typically the fully
+  qualified name of the DWARF Debugging Information Entry (DIE).
+- `value`: Provides rule-specific data.
+
+The following helper macro, for example, can be used to specify rules
+in the source code::
+
+	#define __KABI_RULE(hint, target, value)                             \
+		static const char __PASTE(__gendwarfksyms_rule_,             \
+					  __COUNTER__)[] __used __aligned(1) \
+			__section(".discard.gendwarfksyms.kabi_rules") =     \
+				"1\0" #hint "\0" #target "\0" #value
+
+
+Currently, only the rules discussed in this section are supported, but
+the format is extensible enough to allow further rules to be added as
+need arises.
+
+4.1.1. Managing definition visibility
+=====================================
+
+A declaration can change into a full definition when additional includes
+are pulled into the translation unit. This changes the versions of any
+symbol that references the type even if the ABI remains unchanged. As
+it may not be possible to drop includes without breaking the build, the
+`declonly` rule can be used to specify a type as declaration-only, even
+if the debugging information contains the full definition.
+
+The rule fields are expected to be as follows:
+
+- `type`: "declonly"
+- `target`: The fully qualified name of the target data structure
+  (as shown in **--dump-dies** output).
+- `value`: This field is ignored.
+
+Using the `__KABI_RULE` macro, this rule can be defined as::
+
+	#define KABI_DECLONLY(fqn) __KABI_RULE(declonly, fqn, )
+
+Example usage::
+
+	struct s {
+		/* definition */
+	};
+
+	KABI_DECLONLY(s);
+
+4.1.2. Adding enumerators
+=========================
+
+For enums, all enumerators and their values are included in calculating
+symbol versions, which becomes a problem if we later need to add more
+enumerators without changing symbol versions. The `enumerator_ignore`
+rule allows us to hide named enumerators from the input.
+
+The rule fields are expected to be as follows:
+
+- `type`: "enumerator_ignore"
+- `target`: The fully qualified name of the target enum
+  (as shown in **--dump-dies** output) and the name of the
+  enumerator field separated by a space.
+- `value`: This field is ignored.
+
+Using the `__KABI_RULE` macro, this rule can be defined as::
+
+	#define KABI_ENUMERATOR_IGNORE(fqn, field) \
+		__KABI_RULE(enumerator_ignore, fqn field, )
+
+Example usage::
+
+	enum e {
+		A, B, C, D,
+	};
+
+	KABI_ENUMERATOR_IGNORE(e, B);
+	KABI_ENUMERATOR_IGNORE(e, C);
+
+If the enum additionally includes an end marker and new values must
+be added in the middle, we may need to use the old value for the last
+enumerator when calculating versions. The `enumerator_value` rule allows
+us to override the value of an enumerator for version calculation:
+
+- `type`: "enumerator_value"
+- `target`: The fully qualified name of the target enum
+  (as shown in **--dump-dies** output) and the name of the
+  enumerator field separated by a space.
+- `value`: Integer value used for the field.
+
+Using the `__KABI_RULE` macro, this rule can be defined as::
+
+	#define KABI_ENUMERATOR_VALUE(fqn, field, value) \
+		__KABI_RULE(enumerator_value, fqn field, value)
+
+Example usage::
+
+	enum e {
+		A, B, C, LAST,
+	};
+
+	KABI_ENUMERATOR_IGNORE(e, C);
+	KABI_ENUMERATOR_VALUE(e, LAST, 2);
+
+4.3. Adding structure members
+=============================
+
+Perhaps the most common ABI compatible change is adding a member to a
+kernel data structure. When changes to a structure are anticipated,
+distribution maintainers can pre-emptively reserve space in the
+structure and take it into use later without breaking the ABI. If
+changes are needed to data structures without reserved space, existing
+alignment holes can potentially be used instead. While kABI rules could
+be added for these type of changes, using unions is typically a more
+natural method. This section describes gendwarfksyms support for using
+reserved space in data structures and hiding members that don't change
+the ABI when calculating symbol versions.
+
+4.3.1. Reserving space and replacing members
+============================================
+
+Space is typically reserved for later use by appending integer types, or
+arrays, to the end of the data structure, but any type can be used. Each
+reserved member needs a unique name, but as the actual purpose is usually
+not known at the time the space is reserved, for convenience, names that
+start with `__kabi_` are left out when calculating symbol versions::
+
+        struct s {
+                long a;
+                long __kabi_reserved_0; /* reserved for future use */
+        };
+
+The reserved space can be taken into use by wrapping the member in a
+union, which includes the original type and the replacement member::
+
+        struct s {
+                long a;
+                union {
+                        long __kabi_reserved_0; /* original type */
+                        struct b b; /* replaced field */
+                };
+        };
+
+If the `__kabi_` naming scheme was used when reserving space, the name
+of the first member of the union must start with `__kabi_reserved`. This
+ensures the original type is used when calculating versions, but the name
+is again left out. The rest of the union is ignored.
+
+If we're replacing a member that doesn't follow this naming convention,
+we also need to preserve the original name to avoid changing versions,
+which we can do by changing the first union member's name to start with
+`__kabi_renamed` followed by the original name.
+
+The examples include `KABI_(RESERVE|USE|REPLACE)*` macros that help
+simplify the process and also ensure the replacement member is correctly
+aligned and its size won't exceed the reserved space.
+
+4.3.2. Hiding members
+=====================
+
+Predicting which structures will require changes during the support
+timeframe isn't always possible, in which case one might have to resort
+to placing new members into existing alignment holes::
+
+        struct s {
+                int a;
+                /* a 4-byte alignment hole */
+                unsigned long b;
+        };
+
+
+While this won't change the size of the data structure, one needs to
+be able to hide the added members from symbol versioning. Similarly
+to reserved fields, this can be accomplished by wrapping the added
+member to a union where one of the fields has a name starting with
+`__kabi_ignored`::
+
+        struct s {
+                int a;
+                union {
+                        char __kabi_ignored_0;
+                        int n;
+                };
+                unsigned long b;
+        };
+
+With **--stable**, both versions produce the same symbol version.
diff --git a/Documentation/kbuild/index.rst b/Documentation/kbuild/index.rst
index cee2f99f734b..e82af05cd652 100644
--- a/Documentation/kbuild/index.rst
+++ b/Documentation/kbuild/index.rst
@@ -21,6 +21,7 @@ Kernel Build System
     reproducible-builds
     gcc-plugins
     llvm
+    gendwarfksyms
 
 .. only::  subproject and html
 
-- 
2.47.1.613.gc27f4b7a9f-goog

Re: [PATCH v7 01/18] tools: Add gendwarfksyms

[Masahiro Yamada]

On Fri, Dec 20, 2024 at 6:07 AM Sami Tolvanen <samitolvanen@google.com> wrote:

> +int main(int argc, char **argv)
> +{
> +       unsigned int n;
> +       int opt;
> +
> +       struct option opts[] = { { "debug", 0, NULL, 'd' },

You can add "static const" to opts[] here.

I like the array initializer formatted like follows:

static const struct option opts[] = {
        { "debug", 0, NULL, 'd' },
        { "dump-dies", 0, &dump_dies, 1 },
        { "help", 0, NULL, 'h' },
        { 0, 0, NULL, 0 }
};





> +                                { "dump-dies", 0, &dump_dies, 1 },
> +                                { "help", 0, NULL, 'h' },
> +                                { 0, 0, NULL, 0 } };
> +



--
Best Regards
Masahiro Yamada

Re: [PATCH v7 02/18] gendwarfksyms: Add address matching

[Masahiro Yamada]

On Fri, Dec 20, 2024 at 6:07 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
> index 7adf2ed9b89b..98febb524dd5 100644
> --- a/scripts/gendwarfksyms/symbols.c
> +++ b/scripts/gendwarfksyms/symbols.c
> @@ -6,8 +6,39 @@
>  #include "gendwarfksyms.h"
>
>  #define SYMBOL_HASH_BITS 12
> +
> +/* struct symbol_addr -> struct symbol */
> +static HASHTABLE_DEFINE(symbol_addrs, 1 << SYMBOL_HASH_BITS);
> +/* name -> struct symbol */

I think this comment addition should belong to 01/18 instead of 02/18.


>  static HASHTABLE_DEFINE(symbol_names, 1 << SYMBOL_HASH_BITS);





-- 
Best Regards
Masahiro Yamada

Re: [PATCH v7 01/18] tools: Add gendwarfksyms

[Sami Tolvanen]

Hi Masahiro,

On Fri, Dec 27, 2024 at 6:02 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Dec 20, 2024 at 6:07 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> > +int main(int argc, char **argv)
> > +{
> > +       unsigned int n;
> > +       int opt;
> > +
> > +       struct option opts[] = { { "debug", 0, NULL, 'd' },
>
> You can add "static const" to opts[] here.
>
> I like the array initializer formatted like follows:
>
> static const struct option opts[] = {
>         { "debug", 0, NULL, 'd' },
>         { "dump-dies", 0, &dump_dies, 1 },
>         { "help", 0, NULL, 'h' },
>         { 0, 0, NULL, 0 }
> };

Sure, I'll change this.

Sami

Re: [PATCH v7 02/18] gendwarfksyms: Add address matching

[Sami Tolvanen]

Hi,

On Sat, Dec 28, 2024 at 4:29 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Dec 20, 2024 at 6:07 AM Sami Tolvanen <samitolvanen@google.com> wrote:
> >
> > diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
> > index 7adf2ed9b89b..98febb524dd5 100644
> > --- a/scripts/gendwarfksyms/symbols.c
> > +++ b/scripts/gendwarfksyms/symbols.c
> > @@ -6,8 +6,39 @@
> >  #include "gendwarfksyms.h"
> >
> >  #define SYMBOL_HASH_BITS 12
> > +
> > +/* struct symbol_addr -> struct symbol */
> > +static HASHTABLE_DEFINE(symbol_addrs, 1 << SYMBOL_HASH_BITS);
> > +/* name -> struct symbol */
>
> I think this comment addition should belong to 01/18 instead of 02/18.

Yeah, agreed. I'll send out v8 with these comments addressed.

Sami