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> Reviewed-by: Petr Pavlu <petr.pavlu@xxxxxxxx> --- 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@xxxxxxxxxx> +L: linux-modules@xxxxxxxxxxxxxxx +L: linux-kbuild@xxxxxxxxxxxxxxx +S: Maintained +F: scripts/gendwarfksyms/ + GENERIC ARCHITECTURE TOPOLOGY M: Sudeep Holla <sudeep.holla@xxxxxxx> L: linux-kernel@xxxxxxxxxxxxxxx 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, ¤t)); + while (!res) { + if (match(¤t)) { + /* <0 = error, 0 = continue, >0 = stop */ + res = checkp(func(state, ¤t)); + if (res) + return res; + } + + res = checkp(dwarf_siblingof(¤t, ¤t)); + } + + 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
