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@xxxxxxxxxx>
---
kernel/module/Kconfig | 8 ++
scripts/Makefile | 1 +
scripts/gendwarfksyms/.gitignore | 2 +
scripts/gendwarfksyms/Makefile | 7 ++
scripts/gendwarfksyms/dwarf.c | 87 +++++++++++++++
scripts/gendwarfksyms/gendwarfksyms.c | 146 ++++++++++++++++++++++++++
scripts/gendwarfksyms/gendwarfksyms.h | 78 ++++++++++++++
7 files changed, 329 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
diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index 4047b6d48255..a506d4ac660f 100644
--- a/kernel/module/Kconfig
+++ b/kernel/module/Kconfig
@@ -168,6 +168,14 @@ config MODVERSIONS
make them incompatible with the kernel you are running. If
unsure, say N.
+config GENDWARFKSYMS
+ bool
+ 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 dccef663ca82..2fd0199662e9 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
# Let clean descend into subdirs
diff --git a/scripts/gendwarfksyms/.gitignore b/scripts/gendwarfksyms/.gitignore
new file mode 100644
index 000000000000..ab8c763b3afe
--- /dev/null
+++ b/scripts/gendwarfksyms/.gitignore
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+/gendwarfksyms
diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
new file mode 100644
index 000000000000..c1389c161f9c
--- /dev/null
+++ b/scripts/gendwarfksyms/Makefile
@@ -0,0 +1,7 @@
+hostprogs-always-y += gendwarfksyms
+
+gendwarfksyms-objs += gendwarfksyms.o
+gendwarfksyms-objs += dwarf.o
+
+HOST_EXTRACFLAGS := -I $(srctree)/tools/include
+HOSTLDLIBS_gendwarfksyms := -ldw -lelf
diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
new file mode 100644
index 000000000000..65a29d0bd8f4
--- /dev/null
+++ b/scripts/gendwarfksyms/dwarf.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 = checkp(dwarf_child(die, ¤t));
+ while (!res) {
+ if (match(¤t))
+ check(func(state, ¤t));
+ res = checkp(dwarf_siblingof(¤t, ¤t));
+ }
+
+ 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));
+}
diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
new file mode 100644
index 000000000000..27f2d6423c45
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -0,0 +1,146 @@
+// 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 <unistd.h>
+#include "gendwarfksyms.h"
+
+/*
+ * Options
+ */
+
+/* Print out debugging information to stderr */
+bool debug;
+
+static const struct {
+ const char *arg;
+ bool *flag;
+ const char **param;
+} options[] = {
+ { "--debug", &debug, NULL },
+};
+
+static int usage(void)
+{
+ error("usage: gendwarfksyms [options] elf-object-file ...");
+ return -1;
+}
+
+static const char *object_files[MAX_INPUT_FILES];
+static unsigned int object_count;
+
+static int parse_options(int argc, const char **argv)
+{
+ for (int i = 1; i < argc; i++) {
+ bool flag = false;
+
+ for (int j = 0; j < ARRAY_SIZE(options); j++) {
+ if (strcmp(argv[i], options[j].arg))
+ continue;
+
+ *options[j].flag = true;
+
+ if (options[j].param) {
+ if (++i >= argc) {
+ error("%s needs an argument",
+ options[j].arg);
+ return -1;
+ }
+
+ *options[j].param = argv[i];
+ }
+
+ flag = true;
+ break;
+ }
+
+ if (!flag)
+ object_files[object_count++] = argv[i];
+ }
+
+ return object_count ? 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) {
+ break; /* 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)
+{
+ unsigned int n;
+
+ if (parse_options(argc, argv) < 0)
+ return usage();
+
+ for (n = 0; n < object_count; n++) {
+ Dwfl *dwfl;
+ int fd;
+
+ fd = open(object_files[n], O_RDONLY);
+ if (fd == -1) {
+ error("open failed for '%s': %s", object_files[n],
+ strerror(errno));
+ return -1;
+ }
+
+ dwfl = dwfl_begin(&callbacks);
+ if (!dwfl) {
+ error("dwfl_begin failed for '%s': %s", object_files[n],
+ dwarf_errmsg(-1));
+ return -1;
+ }
+
+ if (!dwfl_report_offline(dwfl, object_files[n], object_files[n],
+ fd)) {
+ error("dwfl_report_offline failed for '%s': %s",
+ object_files[n], 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'",
+ object_files[n]);
+ return -1;
+ }
+
+ dwfl_end(dwfl);
+ close(fd);
+ }
+
+ return 0;
+}
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
new file mode 100644
index 000000000000..5ab7ce7d4efb
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -0,0 +1,78 @@
+/* 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;
+
+#define MAX_INPUT_FILES 128
+
+/*
+ * 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, test, rv) \
+ ({ \
+ int __res = expr; \
+ if (test) { \
+ error("`%s` failed: %d", #expr, __res); \
+ return rv; \
+ } \
+ __res; \
+ })
+
+/* Error == non-zero values */
+#define check(expr) __check(expr, __res, -1)
+/* Error == negative values */
+#define checkp(expr) __check(expr, __res < 0, __res)
+
+/*
+ * dwarf.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 */
--
2.46.0.184.g6999bdac58-goog
