diff mbox series

[v3,03/20] tools: Add gendwarfksyms

Message ID 20240923181846.549877-25-samitolvanen@google.com (mailing list archive)
State Handled Elsewhere
Headers show
Series Implement DWARF modversions | expand

Commit Message

Sami Tolvanen Sept. 23, 2024, 6:18 p.m. UTC 
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>
---
 kernel/module/Kconfig                 |   8 ++
 scripts/Makefile                      |   1 +
 scripts/gendwarfksyms/.gitignore      |   2 +
 scripts/gendwarfksyms/Makefile        |   8 ++
 scripts/gendwarfksyms/dwarf.c         | 166 ++++++++++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.c | 132 ++++++++++++++++++++
 scripts/gendwarfksyms/gendwarfksyms.h |  97 +++++++++++++++
 scripts/gendwarfksyms/symbols.c       |  82 +++++++++++++
 8 files changed, 496 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

Comments

Petr Pavlu Oct. 1, 2024, 2:04 p.m. UTC | #1 
On 9/23/24 20:18, Sami Tolvanen wrote:
> 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>
> ---
>  kernel/module/Kconfig                 |   8 ++
>  scripts/Makefile                      |   1 +
>  scripts/gendwarfksyms/.gitignore      |   2 +
>  scripts/gendwarfksyms/Makefile        |   8 ++
>  scripts/gendwarfksyms/dwarf.c         | 166 ++++++++++++++++++++++++++
>  scripts/gendwarfksyms/gendwarfksyms.c | 132 ++++++++++++++++++++
>  scripts/gendwarfksyms/gendwarfksyms.h |  97 +++++++++++++++
>  scripts/gendwarfksyms/symbols.c       |  82 +++++++++++++
>  8 files changed, 496 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/kernel/module/Kconfig b/kernel/module/Kconfig
> index ccdbd1bc12aa..c3a0172a909f 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 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..096a334fa5b3
> --- /dev/null
> +++ b/scripts/gendwarfksyms/gendwarfksyms.c
> @@ -0,0 +1,132 @@
> +// 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));
> +			return -1;
> +		}
> +
> +		dwfl = dwfl_begin(&callbacks);
> +		if (!dwfl) {
> +			error("dwfl_begin failed for '%s': %s", argv[n],
> +			      dwarf_errmsg(-1));
> +			return -1;
> +		}
> +
> +		if (!dwfl_report_offline(dwfl, argv[n], argv[n], fd)) {
> +			error("dwfl_report_offline failed for '%s': %s",
> +			      argv[n], dwarf_errmsg(-1));
> +			return -1;
> +		}
> +
> +		dwfl_report_end(dwfl, NULL, NULL);
> +
> +		if (dwfl_getmodules(dwfl, &process_module, NULL, 0)) {
> +			error("dwfl_getmodules failed for '%s'", argv[n]);
> +			return -1;
> +		}

Nit: The four error() calls don't need to be followed by 'return -1;'
since the function now calls exit(1).

> +
> +		dwfl_end(dwfl);
> +	}
> +
> +	return 0;
> +}
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
> new file mode 100644
> index 000000000000..1a10d18f178e
> --- /dev/null
> +++ b/scripts/gendwarfksyms/gendwarfksyms.h
> @@ -0,0 +1,97 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2024 Google LLC
> + */
> +
> +#include <dwarf.h>
> +#include <elfutils/libdw.h>
> +#include <elfutils/libdwfl.h>
> +#include <inttypes.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <string.h>
> +
> +#include <hash.h>
> +#include <hashtable.h>
> +#include <list.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);
> +
> +/*
> + * 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..1809be93d18c
> --- /dev/null
> +++ b/scripts/gendwarfksyms/symbols.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2024 Google LLC
> + */
> +
> +#include "gendwarfksyms.h"
> +
> +#define SYMBOL_HASH_BITS 15
> +static HASHTABLE_DEFINE(symbol_names, 1 << SYMBOL_HASH_BITS);
> +
> +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,
> +				    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 checkp(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;
> +}

Nit: The code inconsistently checks for a potential error from the
function for_each(). Looking at the whole series, the value is checked
using checkp() in functions symbol_set_crc(), symbol_set_ptr(),
symbol_set_die(), is_exported(), but not in symbol_get() and
elf_set_symbol_addr(). It would be good to unify this, or perhaps even
make for_each() return an unsigned int to indicate it never fails?

Looks otherwise ok to me, feel free to add:
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Sami Tolvanen Oct. 1, 2024, 7:59 p.m. UTC | #2 
Hi Petr,

On Tue, Oct 1, 2024 at 2:04 PM Petr Pavlu <petr.pavlu@suse.com> wrote:
>
> On 9/23/24 20:18, Sami Tolvanen wrote:
> > +             if (dwfl_getmodules(dwfl, &process_module, NULL, 0)) {
> > +                     error("dwfl_getmodules failed for '%s'", argv[n]);
> > +                     return -1;
> > +             }
>
> Nit: The four error() calls don't need to be followed by 'return -1;'
> since the function now calls exit(1).

Good catch, I forgot to clean these up. I'll fix these.

> > +     for_each(name, get_symbol, &sym);
> > +     return sym;
> > +}
>
> Nit: The code inconsistently checks for a potential error from the
> function for_each(). Looking at the whole series, the value is checked
> using checkp() in functions symbol_set_crc(), symbol_set_ptr(),
> symbol_set_die(), is_exported(), but not in symbol_get() and
> elf_set_symbol_addr(). It would be good to unify this, or perhaps even
> make for_each() return an unsigned int to indicate it never fails?

True, there's no need to use check() anymore here. I'll change the
return value to unsigned int and clean up the error handling.

Sami
diff mbox series

Patch

diff --git a/kernel/module/Kconfig b/kernel/module/Kconfig
index ccdbd1bc12aa..c3a0172a909f 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 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..096a334fa5b3
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.c
@@ -0,0 +1,132 @@ 
+// 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));
+			return -1;
+		}
+
+		dwfl = dwfl_begin(&callbacks);
+		if (!dwfl) {
+			error("dwfl_begin failed for '%s': %s", argv[n],
+			      dwarf_errmsg(-1));
+			return -1;
+		}
+
+		if (!dwfl_report_offline(dwfl, argv[n], argv[n], fd)) {
+			error("dwfl_report_offline failed for '%s': %s",
+			      argv[n], dwarf_errmsg(-1));
+			return -1;
+		}
+
+		dwfl_report_end(dwfl, NULL, NULL);
+
+		if (dwfl_getmodules(dwfl, &process_module, NULL, 0)) {
+			error("dwfl_getmodules failed for '%s'", argv[n]);
+			return -1;
+		}
+
+		dwfl_end(dwfl);
+	}
+
+	return 0;
+}
diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
new file mode 100644
index 000000000000..1a10d18f178e
--- /dev/null
+++ b/scripts/gendwarfksyms/gendwarfksyms.h
@@ -0,0 +1,97 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include <dwarf.h>
+#include <elfutils/libdw.h>
+#include <elfutils/libdwfl.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <hash.h>
+#include <hashtable.h>
+#include <list.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);
+
+/*
+ * 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..1809be93d18c
--- /dev/null
+++ b/scripts/gendwarfksyms/symbols.c
@@ -0,0 +1,82 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2024 Google LLC
+ */
+
+#include "gendwarfksyms.h"
+
+#define SYMBOL_HASH_BITS 15
+static HASHTABLE_DEFINE(symbol_names, 1 << SYMBOL_HASH_BITS);
+
+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,
+				    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 checkp(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;
+}