[PATCH 01/15] tools: Add gendwarfksyms

Sami Tolvanen
2024-06-17T17:58:28Z

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. This tool is needed mainly for Rust
kernel module compatibility.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
tools/Makefile | 11 +--
tools/gendwarfksyms/Build | 2 +
tools/gendwarfksyms/Makefile | 49 +++++++++++
tools/gendwarfksyms/gendwarfksyms.c | 128 ++++++++++++++++++++++++++++
tools/gendwarfksyms/gendwarfksyms.h | 71 +++++++++++++++
tools/gendwarfksyms/types.c | 87 +++++++++++++++++++
6 files changed, 343 insertions(+), 5 deletions(-)
create mode 100644 tools/gendwarfksyms/Build
create mode 100644 tools/gendwarfksyms/Makefile
create mode 100644 tools/gendwarfksyms/gendwarfksyms.c
create mode 100644 tools/gendwarfksyms/gendwarfksyms.h
create mode 100644 tools/gendwarfksyms/types.c

diff --git a/tools/Makefile b/tools/Makefile
index 276f5d0d53a4..60806ff753b7 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -17,6 +17,7 @@ help:
@echo ' firewire - the userspace part of nosy, an IEEE-1394 traffic sniffer'
@echo ' firmware - Firmware tools'
@echo ' freefall - laptop accelerometer program for disk protection'
+ @echo ' gendwarfksyms - generates symbol versions from DWARF'
@echo ' gpio - GPIO tools'
@echo ' hv - tools used when in Hyper-V clients'
@echo ' iio - IIO tools'
@@ -68,7 +69,7 @@ acpi: FORCE
cpupower: FORCE
$(call descend,power/$@)

-counter firewire hv guest bootconfig spi usb virtio mm bpf iio gpio objtool leds wmi pci firmware debugging tracing: FORCE
+counter firewire hv guest bootconfig spi usb virtio mm bpf iio gendwarfksyms gpio objtool leds wmi pci firmware debugging tracing: FORCE
$(call descend,$@)

bpf/%: FORCE
@@ -154,8 +155,8 @@ freefall_install:
kvm_stat_install:
$(call descend,kvm/$(@:_install=),install)

-install: acpi_install counter_install cpupower_install gpio_install \
- hv_install firewire_install iio_install \
+install: acpi_install counter_install cpupower_install gendwarfksyms_install \
+ gpio_install hv_install firewire_install iio_install \
perf_install selftests_install turbostat_install usb_install \
virtio_install mm_install bpf_install x86_energy_perf_policy_install \
tmon_install freefall_install objtool_install kvm_stat_install \
@@ -168,7 +169,7 @@ acpi_clean:
cpupower_clean:
$(call descend,power/cpupower,clean)

-counter_clean hv_clean firewire_clean bootconfig_clean spi_clean usb_clean virtio_clean mm_clean wmi_clean bpf_clean iio_clean gpio_clean objtool_clean leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
+counter_clean hv_clean firewire_clean bootconfig_clean spi_clean usb_clean virtio_clean mm_clean wmi_clean bpf_clean iio_clean gendwarfksyms_clean gpio_clean objtool_clean leds_clean pci_clean firmware_clean debugging_clean tracing_clean:
$(call descend,$(@:_clean=),clean)

libapi_clean:
@@ -211,7 +212,7 @@ build_clean:
clean: acpi_clean counter_clean cpupower_clean hv_clean firewire_clean \
perf_clean selftests_clean turbostat_clean bootconfig_clean spi_clean usb_clean virtio_clean \
mm_clean bpf_clean iio_clean x86_energy_perf_policy_clean tmon_clean \
- freefall_clean build_clean libbpf_clean libsubcmd_clean \
+ freefall_clean build_clean libbpf_clean libsubcmd_clean gendwarfksyms_clean \
gpio_clean objtool_clean leds_clean wmi_clean pci_clean firmware_clean debugging_clean \
intel-speed-select_clean tracing_clean thermal_clean thermometer_clean thermal-engine_clean

diff --git a/tools/gendwarfksyms/Build b/tools/gendwarfksyms/Build
new file mode 100644
index 000000000000..805591b6df80
--- /dev/null
+++ b/tools/gendwarfksyms/Build
@@ -0,0 +1,2 @@
+gendwarfksyms-y += gendwarfksyms.o
+gendwarfksyms-y += types.o
diff --git a/tools/gendwarfksyms/Makefile b/tools/gendwarfksyms/Makefile
new file mode 100644
index 000000000000..1138ebd8bd0f
--- /dev/null
+++ b/tools/gendwarfksyms/Makefile
@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: GPL-2.0
+include ../scripts/Makefile.include
+include ../scripts/Makefile.arch
+
+ifeq ($(srctree),)
+srctree := $(patsubst %/,%,$(dir $(CURDIR)))
+srctree := $(patsubst %/,%,$(dir $(srctree)))
+endif
+
+GENDWARFKSYMS := $(OUTPUT)gendwarfksyms
+GENDWARFKSYMS_IN := $(GENDWARFKSYMS)-in.o
+
+LIBDW_FLAGS := $(shell $(HOSTPKG_CONFIG) libdw --cflags 2>/dev/null)
+LIBDW_LIBS := $(shell $(HOSTPKG_CONFIG) libdw --libs 2>/dev/null || echo -ldw -lelf)
+
+all: $(GENDWARFKSYMS)
+
+INCLUDES := -I$(srctree)/tools/include
+
+WARNINGS := -Wall -Wno-unused-value
+GENDWARFKSYMS_CFLAGS := -Werror $(WARNINGS) $(KBUILD_HOSTCFLAGS) -g $(INCLUDES) $(LIBDW_FLAGS)
+GENDWARFKSYMS_LDFLAGS := $(LIBDW_LIBS) $(KBUILD_HOSTLDFLAGS)
+
+# Always want host compilation.
+HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)"
+
+ifeq ($(V),1)
+ Q =
+else
+ Q = @
+endif
+
+export srctree OUTPUT
+include $(srctree)/tools/build/Makefile.include
+
+$(GENDWARFKSYMS_IN): FORCE
+ $(Q)$(MAKE) $(build)=gendwarfksyms $(HOST_OVERRIDES) CFLAGS="$(GENDWARFKSYMS_CFLAGS)" \
+ LDFLAGS="$(GENDWARFKSYMS_LDFLAGS)"
+
+
+$(GENDWARFKSYMS): $(GENDWARFKSYMS_IN)
+ $(QUIET_LINK)$(HOSTCC) $(GENDWARFKSYMS_IN) $(GENDWARFKSYMS_LDFLAGS) -o $@
+
+clean:
+ $(call QUIET_CLEAN, gendwarfksyms) $(RM) $(GENDWARFKSYMS)
+
+FORCE:
+
+.PHONY: clean FORCE
diff --git a/tools/gendwarfksyms/gendwarfksyms.c b/tools/gendwarfksyms/gendwarfksyms.c
new file mode 100644
index 000000000000..4a2dea307849
--- /dev/null
+++ b/tools/gendwarfksyms/gendwarfksyms.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <fcntl.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <string.h>
+#include "gendwarfksyms.h"
+
+/*
+ * Options
+ */
+
+/* Print type descriptions and debugging output to stderr */
+bool debug;
+
+static const struct {
+ const char *arg;
+ bool *flag;
+} options[] = {
+ { "--debug", &debug },
+};
+
+static int usage(void)
+{
+ error("usage: gendwarfksyms [options] elf-object-file < symbol-list");
+ return -1;
+}
+
+static int parse_options(int argc, const char **argv, const char **filename)
+{
+ *filename = NULL;
+
+ for (int i = 1; i < argc; i++) {
+ bool found = false;
+
+ for (int j = 0; j < ARRAY_SIZE(options); j++) {
+ if (!strcmp(argv[i], options[j].arg)) {
+ *options[j].flag = true;
+ found = true;
+ break;
+ }
+ }
+
+ if (!found) {
+ if (!*filename)
+ *filename = argv[i];
+ else
+ return -1;
+ }
+ }
+
+ return *filename ? 0 : -1;
+}
+
+static int process_modules(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?");
+ return -1;
+ } else if (res == 1) {
+ return DWARF_CB_OK; /* No more units */
+ }
+
+ check(process_module(mod, dbg, &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, const char **argv)
+{
+ const char *filename = NULL;
+ Dwfl *dwfl;
+ int fd;
+
+ if (parse_options(argc, argv, &filename) < 0)
+ return usage();
+
+ fd = open(filename, O_RDONLY);
+ if (fd == -1) {
+ error("open failed for '%s': %s", filename, strerror(errno));
+ return -1;
+ }
+
+ dwfl = dwfl_begin(&callbacks);
+ if (!dwfl) {
+ error("dwfl_begin failed for '%s': %s", filename,
+ dwarf_errmsg(-1));
+ return -1;
+ }
+
+ if (!dwfl_report_offline(dwfl, filename, filename, fd)) {
+ error("dwfl_report_offline failed for '%s': %s", filename,
+ dwarf_errmsg(-1));
+ return -1;
+ }
+
+ dwfl_report_end(dwfl, NULL, NULL);
+
+ if (dwfl_getmodules(dwfl, &process_modules, NULL, 0)) {
+ error("dwfl_getmodules failed for '%s'", filename);
+ return -1;
+ }
+
+ dwfl_end(dwfl);
+
+ return 0;
+}
diff --git a/tools/gendwarfksyms/gendwarfksyms.h b/tools/gendwarfksyms/gendwarfksyms.h
new file mode 100644
index 000000000000..44e94f1d9671
--- /dev/null
+++ b/tools/gendwarfksyms/gendwarfksyms.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <dwarf.h>
+#include <elfutils/libdw.h>
+#include <elfutils/libdwfl.h>
+#include <linux/hashtable.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifndef __GENDWARFKSYMS_H
+#define __GENDWARFKSYMS_H
+
+/*
+ * Options -- in gendwarfksyms.c
+ */
+extern bool debug;
+
+/*
+ * 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, ...) __println("error: ", format, ##__VA_ARGS__)
+
+/*
+ * Error handling helpers
+ */
+#define check(expr) \
+ ({ \
+ int __res = expr; \
+ if (__res < 0) { \
+ error("`%s` failed: %d", #expr, __res); \
+ return __res; \
+ } \
+ __res; \
+ })
+
+/*
+ * types.c
+ */
+
+struct state {
+ Dwfl_Module *mod;
+ Dwarf *dbg;
+};
+
+typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
+typedef bool (*die_match_callback_t)(Dwarf_Die *die);
+extern bool match_all(Dwarf_Die *die);
+
+extern int process_die_container(struct state *state, Dwarf_Die *die,
+ die_callback_t func,
+ die_match_callback_t match);
+
+extern int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie);
+
+#endif /* __GENDWARFKSYMS_H */
diff --git a/tools/gendwarfksyms/types.c b/tools/gendwarfksyms/types.c
new file mode 100644
index 000000000000..2a8e45ae911c
--- /dev/null
+++ b/tools/gendwarfksyms/types.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+/*
+ * Type string processing
+ */
+static int process(struct state *state, const char *s)
+{
+ s = s ?: "<null>";
+
+ if (debug)
+ fputs(s, stderr);
+
+ return 0;
+}
+
+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 = check(dwarf_child(die, &current));
+ while (!res) {
+ if (match(&current))
+ check(func(state, &current));
+ res = check(dwarf_siblingof(&current, &current));
+ }
+
+ return 0;
+}
+
+/*
+ * Symbol processing
+ */
+static int process_subprogram(struct state *state, Dwarf_Die *die)
+{
+ return check(process(state, "subprogram;\n"));
+}
+
+static int process_variable(struct state *state, Dwarf_Die *die)
+{
+ return check(process(state, "variable;\n"));
+}
+
+static int process_exported_symbols(struct state *state, 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(
+ state, die, process_exported_symbols, match_all));
+
+ /* Possible exported symbols */
+ case DW_TAG_subprogram:
+ case DW_TAG_variable:
+ if (tag == DW_TAG_subprogram)
+ check(process_subprogram(state, die));
+ else
+ check(process_variable(state, die));
+
+ return 0;
+ default:
+ return 0;
+ }
+}
+
+int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie)
+{
+ struct state state = { .mod = mod, .dbg = dbg };
+
+ return check(process_die_container(
+ &state, cudie, process_exported_symbols, match_all));
+}
--
2.45.2.627.g7a2c4fd464-goog