[PATCH v2 02/19] gendwarfksyms: Add symbol list handling

[Sami Tolvanen <samitolvanen@google.com>]

Add support for passing a list of exported symbols to gendwarfksyms
via stdin and filter out non-exported symbols from the output.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 scripts/gendwarfksyms/Makefile        |  1 +
 scripts/gendwarfksyms/dwarf.c         | 53 ++++++++++++++-
 scripts/gendwarfksyms/gendwarfksyms.c |  4 +-
 scripts/gendwarfksyms/gendwarfksyms.h | 21 ++++++
 scripts/gendwarfksyms/symbols.c       | 96 +++++++++++++++++++++++++++
 5 files changed, 171 insertions(+), 4 deletions(-)
 create mode 100644 scripts/gendwarfksyms/symbols.c

diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
index c1389c161f9c..623f8fc975ea 100644
--- a/scripts/gendwarfksyms/Makefile
+++ b/scripts/gendwarfksyms/Makefile
@@ -2,6 +2,7 @@ hostprogs-always-y += gendwarfksyms
 
 gendwarfksyms-objs += gendwarfksyms.o
 gendwarfksyms-objs += dwarf.o
+gendwarfksyms-objs += symbols.o
 
 HOST_EXTRACFLAGS := -I $(srctree)/tools/include
 HOSTLDLIBS_gendwarfksyms := -ldw -lelf
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
index 65a29d0bd8f4..71cfab0553da 100644
--- a/scripts/gendwarfksyms/dwarf.c
+++ b/scripts/gendwarfksyms/dwarf.c
@@ -5,6 +5,48 @@
 
 #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);
+}
+
+static const char *get_name(Dwarf_Die *die)
+{
+	Dwarf_Attribute attr;
+
+	/* rustc uses DW_AT_linkage_name for exported symbols */
+	if (dwarf_attr(die, DW_AT_linkage_name, &attr) ||
+	    dwarf_attr(die, DW_AT_name, &attr)) {
+		return dwarf_formstring(&attr);
+	}
+
+	return NULL;
+}
+
+static bool is_export_symbol(struct state *state, Dwarf_Die *die)
+{
+	Dwarf_Die *source = die;
+	Dwarf_Die origin;
+
+	state->sym = NULL;
+
+	/* 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_name(die));
+
+	/* Look up using the origin name if there are no matches. */
+	if (!state->sym && source != die)
+		state->sym = symbol_get(get_name(source));
+
+	state->die = *source;
+	return !!state->sym;
+}
+
 /*
  * Type string processing
  */
@@ -40,7 +82,7 @@ int process_die_container(struct state *state, Dwarf_Die *die,
 }
 
 /*
- * Symbol processing
+ * Exported symbol processing
  */
 static int process_subprogram(struct state *state, Dwarf_Die *die)
 {
@@ -67,10 +109,15 @@ static int process_exported_symbols(struct state *state, Dwarf_Die *die)
 	/* Possible exported symbols */
 	case DW_TAG_subprogram:
 	case DW_TAG_variable:
+		if (!is_export_symbol(state, die))
+			return 0;
+
+		debug("%s", state->sym->name);
+
 		if (tag == DW_TAG_subprogram)
-			check(process_subprogram(state, die));
+			check(process_subprogram(state, &state->die));
 		else
-			check(process_variable(state, die));
+			check(process_variable(state, &state->die));
 
 		return 0;
 	default:
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
index 27f2d6423c45..d209b237766b 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.c
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -27,7 +27,7 @@ static const struct {
 
 static int usage(void)
 {
-	error("usage: gendwarfksyms [options] elf-object-file ...");
+	error("usage: gendwarfksyms [options] elf-object-file ... < symbol-list");
 	return -1;
 }
 
@@ -105,6 +105,8 @@ int main(int argc, const char **argv)
 	if (parse_options(argc, argv) < 0)
 		return usage();
 
+	check(symbol_read_exports(stdin));
+
 	for (n = 0; n < object_count; n++) {
 		Dwfl *dwfl;
 		int fd;
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
index 5ab7ce7d4efb..03f3e408a839 100644
--- a/scripts/gendwarfksyms/gendwarfksyms.h
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -7,9 +7,11 @@
 #include <elfutils/libdw.h>
 #include <elfutils/libdwfl.h>
 #include <linux/hashtable.h>
+#include <linux/jhash.h>
 #include <inttypes.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <string.h>
 
 #ifndef __GENDWARFKSYMS_H
 #define __GENDWARFKSYMS_H
@@ -56,6 +58,23 @@ extern bool debug;
 /* Error == negative values */
 #define checkp(expr) __check(expr, __res < 0, __res)
 
+/*
+ * symbols.c
+ */
+
+static inline u32 name_hash(const char *name)
+{
+	return jhash(name, strlen(name), 0);
+}
+
+struct symbol {
+	const char *name;
+	struct hlist_node name_hash;
+};
+
+extern int symbol_read_exports(FILE *file);
+extern struct symbol *symbol_get(const char *name);
+
 /*
  * dwarf.c
  */
@@ -63,6 +82,8 @@ extern bool debug;
 struct state {
 	Dwfl_Module *mod;
 	Dwarf *dbg;
+	struct symbol *sym;
+	Dwarf_Die die;
 };
 
 typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
new file mode 100644
index 000000000000..673ad9cf9e77
--- /dev/null
+++ b/scripts/gendwarfksyms/symbols.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+#define SYMBOL_HASH_BITS 15
+static DEFINE_HASHTABLE(symbol_names, SYMBOL_HASH_BITS);
+
+typedef int (*symbol_callback_t)(struct symbol *, void *arg);
+
+static 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,
+				    name_hash(name)) {
+		if (strcmp(match->name, name))
+			continue;
+
+		if (func)
+			check(func(match, data));
+
+		return 1;
+	}
+
+	return 0;
+}
+
+static bool is_exported(const char *name)
+{
+	return checkp(for_each(name, NULL, NULL)) > 0;
+}
+
+int 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);
+			return -1;
+		}
+
+		free(line);
+		line = NULL;
+
+		if (is_exported(name))
+			continue; /* Ignore duplicates */
+
+		sym = malloc(sizeof(struct symbol));
+		if (!sym) {
+			error("malloc failed");
+			return -1;
+		}
+
+		sym->name = name;
+		name = NULL;
+
+		hash_add(symbol_names, &sym->name_hash, name_hash(sym->name));
+		++nsym;
+
+		debug("%s", sym->name);
+	}
+
+	if (line)
+		free(line);
+
+	debug("%d exported symbols", nsym);
+	return 0;
+}
+
+static int get_symbol(struct symbol *sym, void *arg)
+{
+	struct symbol **res = arg;
+
+	*res = sym;
+	return 0;
+}
+
+struct symbol *symbol_get(const char *name)
+{
+	struct symbol *sym = NULL;
+
+	for_each(name, get_symbol, &sym);
+	return sym;
+}
-- 
2.46.0.184.g6999bdac58-goog