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objtool/klp: Add "objtool klp checksum" subcommand

Browse Source 
Move the checksum functionality out of the main objtool command into a
new "objtool klp checksum" subcommand.

This has the benefit of making the code (and the patch generation
process itself) more modular.

For bisectability, both "objtool --checksum" and "objtool klp checksum"
work for now.  The former will be removed after klp-build has been
converted to use the new subcommand.

Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
This commit is contained in:
Josh Poimboeuf 2026-04-03 13:08:32 -07:00
parent a5b6612332
commit e10764614a
8 changed files with 269 additions and 205 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/objtool/Build
View File

@ -12,7 +12,7 @@ objtool-$(BUILD_DISAS) += disas.o
objtool-$(BUILD_DISAS) += trace.o
objtool-$(BUILD_ORC) += orc_gen.o orc_dump.o
objtool-$(BUILD_KLP) += builtin-klp.o klp-diff.o klp-post-link.o
objtool-$(BUILD_KLP) += builtin-klp.o klp-checksum.o klp-diff.o klp-post-link.o
objtool-y += libstring.o
objtool-y += libctype.o

1
tools/objtool/builtin-klp.c
View File

@ -13,6 +13,7 @@ struct subcmd {
};
static struct subcmd subcmds[] = {
{ "checksum", "Generate per-function checksums", cmd_klp_checksum, },
{ "diff", "Generate binary diff of two object files", cmd_klp_diff, },
{ "post-link", "Finalize klp symbols/relocs after module linking", cmd_klp_post_link, },
};

205
tools/objtool/check.c
View File

@ -64,8 +64,8 @@ struct instruction *next_insn_same_sec(struct objtool_file *file,
return insn;
}
static struct instruction *next_insn_same_func(struct objtool_file *file,
struct instruction *insn)
struct instruction *next_insn_same_func(struct objtool_file *file,
struct instruction *insn)
{
struct instruction *next = next_insn_same_sec(file, insn);
struct symbol *func = insn_func(insn);
@ -113,10 +113,6 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file,
for_each_sec(file->elf, __sec) \
sec_for_each_insn(file, __sec, insn)
#define func_for_each_insn(file, func, insn) \
for (insn = find_insn(file, func->sec, func->offset); \
insn; \
insn = next_insn_same_func(file, insn))
#define sym_for_each_insn(file, sym, insn) \
for (insn = find_insn(file, sym->sec, sym->offset); \
@ -1023,56 +1019,6 @@ static int create_direct_call_sections(struct objtool_file *file)
return 0;
}
#ifdef BUILD_KLP
static int create_sym_checksum_section(struct objtool_file *file)
{
struct section *sec;
struct symbol *sym;
unsigned int idx = 0;
struct sym_checksum *checksum;
size_t entsize = sizeof(struct sym_checksum);
sec = find_section_by_name(file->elf, ".discard.sym_checksum");
if (sec) {
if (!opts.dryrun)
WARN("file already has .discard.sym_checksum section, skipping");
return 0;
}
for_each_sym(file->elf, sym)
if (sym->csum.checksum)
idx++;
sec = elf_create_section_pair(file->elf, ".discard.sym_checksum", entsize,
idx, idx);
if (!sec)
return -1;
idx = 0;
for_each_sym(file->elf, sym) {
if (!sym->csum.checksum)
continue;
if (!elf_init_reloc(file->elf, sec->rsec, idx, idx * entsize,
sym, 0, R_TEXT64))
return -1;
checksum = (struct sym_checksum *)sec->data->d_buf + idx;
checksum->addr = 0; /* reloc */
checksum->checksum = sym->csum.checksum;
mark_sec_changed(file->elf, sec, true);
idx++;
}
return 0;
}
#else
static int create_sym_checksum_section(struct objtool_file *file) { return -EINVAL; }
#endif
/*
* Warnings shouldn't be reported for ignored functions.
*/
@ -3672,153 +3618,6 @@ static bool skip_alt_group(struct instruction *insn)
return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;
}
#ifdef BUILD_KLP
static int checksum_debug_init(struct objtool_file *file)
{
char *dup, *s;
if (!opts.debug_checksum)
return 0;
dup = strdup(opts.debug_checksum);
if (!dup) {
ERROR_GLIBC("strdup");
return -1;
}
s = dup;
while (*s) {
bool found = false;
struct symbol *sym;
char *comma;
comma = strchr(s, ',');
if (comma)
*comma = '\0';
for_each_sym_by_name(file->elf, s, sym) {
if (!is_func_sym(sym))
continue;
sym->debug_checksum = 1;
found = true;
}
if (!found)
WARN("--debug-checksum: can't find '%s'", s);
if (!comma)
break;
s = comma + 1;
}
free(dup);
return 0;
}
static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
struct instruction *insn)
{
struct reloc *reloc = insn_reloc(file, insn);
struct alternative *alt;
unsigned long offset;
struct symbol *sym;
static bool in_alt;
if (insn->fake)
return;
checksum_update(func, insn, insn->sec->data->d_buf + insn->offset, insn->len);
if (!reloc) {
struct symbol *call_dest = insn_call_dest(insn);
if (call_dest)
checksum_update(func, insn, call_dest->demangled_name,
strlen(call_dest->demangled_name));
goto alts;
}
sym = reloc->sym;
offset = arch_insn_adjusted_addend(insn, reloc);
if (is_string_sec(sym->sec)) {
char *str;
str = sym->sec->data->d_buf + sym->offset + offset;
checksum_update(func, insn, str, strlen(str));
goto alts;
}
if (is_sec_sym(sym)) {
sym = find_symbol_containing(reloc->sym->sec, offset);
if (!sym)
goto alts;
offset -= sym->offset;
}
checksum_update(func, insn, sym->demangled_name, strlen(sym->demangled_name));
checksum_update(func, insn, &offset, sizeof(offset));
alts:
for (alt = insn->alts; alt; alt = alt->next) {
struct alt_group *alt_group = alt->insn->alt_group;
/* Prevent __ex_table recursion, e.g. LOAD_SEGMENT() */
if (in_alt)
break;
in_alt = true;
checksum_update(func, insn, &alt->type, sizeof(alt->type));
if (alt_group && alt_group->orig_group) {
struct instruction *alt_insn;
checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
checksum_update_insn(file, func, alt_insn);
if (!alt_group->last_insn || alt_insn == alt_group->last_insn)
break;
}
} else {
checksum_update_insn(file, func, alt->insn);
}
in_alt = false;
}
}
static int calculate_checksums(struct objtool_file *file)
{
struct instruction *insn;
struct symbol *func;
if (checksum_debug_init(file))
return -1;
for_each_sym(file->elf, func) {
/*
* Skip cold subfunctions and aliases: they share the
* parent's checksum via func_for_each_insn() which
* follows func->cfunc into the cold subfunction.
*/
if (!is_func_sym(func) || is_cold_func(func) ||
is_alias_sym(func) || !func->len)
continue;
checksum_init(func);
func_for_each_insn(file, func, insn)
checksum_update_insn(file, func, insn);
checksum_finish(func);
}
return 0;
}
#endif /* BUILD_KLP */
static int validate_branch(struct objtool_file *file, struct symbol *func,
struct instruction *insn, struct insn_state state);
static int do_validate_branch(struct objtool_file *file, struct symbol *func,

6
tools/objtool/include/objtool/check.h
View File

@ -144,6 +144,12 @@ struct instruction *find_insn(struct objtool_file *file,
struct section *sec, unsigned long offset);
struct instruction *next_insn_same_sec(struct objtool_file *file, struct instruction *insn);
struct instruction *next_insn_same_func(struct objtool_file *file, struct instruction *insn);
#define func_for_each_insn(file, func, insn) \
for (insn = find_insn(file, func->sec, func->offset); \
insn; \
insn = next_insn_same_func(file, insn))
#define sec_for_each_insn(file, _sec, insn) \
for (insn = find_insn(file, _sec, 0); \

4
tools/objtool/include/objtool/checksum.h
View File

@ -31,9 +31,13 @@ static inline void checksum_finish(struct symbol *func)
}
}
int calculate_checksums(struct objtool_file *file);
int create_sym_checksum_section(struct objtool_file *file);
#else /* !BUILD_KLP */
static inline int calculate_checksums(struct objtool_file *file) { return -ENOSYS; }
static inline int create_sym_checksum_section(struct objtool_file *file) { return -EINVAL; }
#endif /* !BUILD_KLP */

1
tools/objtool/include/objtool/klp.h
View File

@ -29,6 +29,7 @@ struct klp_reloc {
u32 type;
};
int cmd_klp_checksum(int argc, const char **argv);
int cmd_klp_diff(int argc, const char **argv);
int cmd_klp_post_link(int argc, const char **argv);

253
tools/objtool/klp-checksum.c Normal file
View File

@ -0,0 +1,253 @@
// SPDX-License-Identifier: GPL-2.0-or-later
#include <string.h>
#include <subcmd/parse-options.h>
#include <objtool/arch.h>
#include <objtool/builtin.h>
#include <objtool/check.h>
#include <objtool/elf.h>
#include <objtool/klp.h>
#include <objtool/objtool.h>
#include <objtool/warn.h>
#include <objtool/checksum.h>
static int checksum_debug_init(struct objtool_file *file)
{
char *dup, *s;
if (!opts.debug_checksum)
return 0;
dup = strdup(opts.debug_checksum);
if (!dup) {
ERROR_GLIBC("strdup");
return -1;
}
s = dup;
while (*s) {
bool found = false;
struct symbol *sym;
char *comma;
comma = strchr(s, ',');
if (comma)
*comma = '\0';
for_each_sym_by_name(file->elf, s, sym) {
if (!is_func_sym(sym))
continue;
sym->debug_checksum = 1;
found = true;
}
if (!found)
WARN("--debug-checksum: can't find '%s'", s);
if (!comma)
break;
s = comma + 1;
}
free(dup);
return 0;
}
static void checksum_update_insn(struct objtool_file *file, struct symbol *func,
struct instruction *insn)
{
struct reloc *reloc = insn_reloc(file, insn);
struct alternative *alt;
unsigned long offset;
struct symbol *sym;
static bool in_alt;
if (insn->fake)
return;
checksum_update(func, insn, insn->sec->data->d_buf + insn->offset, insn->len);
if (!reloc) {
struct symbol *call_dest = insn_call_dest(insn);
if (call_dest)
checksum_update(func, insn, call_dest->demangled_name,
strlen(call_dest->demangled_name));
goto alts;
}
sym = reloc->sym;
offset = arch_insn_adjusted_addend(insn, reloc);
if (is_string_sec(sym->sec)) {
char *str;
str = sym->sec->data->d_buf + sym->offset + offset;
checksum_update(func, insn, str, strlen(str));
goto alts;
}
if (is_sec_sym(sym)) {
sym = find_symbol_containing(reloc->sym->sec, offset);
if (!sym)
goto alts;
offset -= sym->offset;
}
checksum_update(func, insn, sym->demangled_name, strlen(sym->demangled_name));
checksum_update(func, insn, &offset, sizeof(offset));
alts:
for (alt = insn->alts; alt; alt = alt->next) {
struct alt_group *alt_group = alt->insn->alt_group;
/* Prevent __ex_table recursion, e.g. LOAD_SEGMENT() */
if (in_alt)
break;
in_alt = true;
checksum_update(func, insn, &alt->type, sizeof(alt->type));
if (alt_group && alt_group->orig_group) {
struct instruction *alt_insn;
checksum_update(func, insn, &alt_group->feature, sizeof(alt_group->feature));
for (alt_insn = alt->insn; alt_insn; alt_insn = next_insn_same_sec(file, alt_insn)) {
checksum_update_insn(file, func, alt_insn);
if (!alt_group->last_insn || alt_insn == alt_group->last_insn)
break;
}
} else {
checksum_update_insn(file, func, alt->insn);
}
in_alt = false;
}
}
int calculate_checksums(struct objtool_file *file)
{
struct instruction *insn;
struct symbol *func;
if (checksum_debug_init(file))
return -1;
for_each_sym(file->elf, func) {
/*
* Skip cold subfunctions and aliases: they share the
* parent's checksum via func_for_each_insn() which
* follows func->cfunc into the cold subfunction.
*/
if (!is_func_sym(func) || is_cold_func(func) ||
is_alias_sym(func) || !func->len)
continue;
checksum_init(func);
func_for_each_insn(file, func, insn)
checksum_update_insn(file, func, insn);
checksum_finish(func);
}
return 0;
}
int create_sym_checksum_section(struct objtool_file *file)
{
struct section *sec;
struct symbol *sym;
unsigned int idx = 0;
struct sym_checksum *checksum;
size_t entsize = sizeof(struct sym_checksum);
sec = find_section_by_name(file->elf, ".discard.sym_checksum");
if (sec) {
if (!opts.dryrun)
WARN("file already has .discard.sym_checksum section, skipping");
return 0;
}
for_each_sym(file->elf, sym)
if (sym->csum.checksum)
idx++;
sec = elf_create_section_pair(file->elf, ".discard.sym_checksum", entsize,
idx, idx);
if (!sec)
return -1;
idx = 0;
for_each_sym(file->elf, sym) {
if (!sym->csum.checksum)
continue;
if (!elf_init_reloc(file->elf, sec->rsec, idx, idx * entsize,
sym, 0, R_TEXT64))
return -1;
checksum = (struct sym_checksum *)sec->data->d_buf + idx;
checksum->addr = 0; /* reloc */
checksum->checksum = sym->csum.checksum;
mark_sec_changed(file->elf, sec, true);
idx++;
}
return 0;
}
static const char * const klp_checksum_usage[] = {
"objtool klp checksum [<options>] file.o",
NULL,
};
int cmd_klp_checksum(int argc, const char **argv)
{
struct objtool_file *file;
int ret;
const struct option options[] = {
OPT_STRING(0, "debug-checksum", &opts.debug_checksum, "funcs", "enable checksum debug output"),
OPT_BOOLEAN(0, "dry-run", &opts.dryrun, "don't write modifications"),
OPT_END(),
};
argc = parse_options(argc, argv, options, klp_checksum_usage, 0);
if (argc != 1)
usage_with_options(klp_checksum_usage, options);
opts.checksum = true;
objname = argv[0];
file = objtool_open_read(objname);
if (!file)
return 1;
ret = decode_file(file);
if (ret)
goto out;
ret = calculate_checksums(file);
if (ret)
goto out;
ret = create_sym_checksum_section(file);
out:
free_insns(file);
if (ret)
return ret;
if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
return 1;
return elf_close(file->elf);
}

2
tools/objtool/klp-diff.c
View File

@ -166,7 +166,7 @@ static int read_sym_checksums(struct elf *elf)
sec = find_section_by_name(elf, ".discard.sym_checksum");
if (!sec) {
ERROR("'%s' missing .discard.sym_checksum section, file not processed by 'objtool --checksum'?",
ERROR("'%s' missing .discard.sym_checksum section, file not processed by 'objtool klp checksum'?",
elf->name);
return -1;
}