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Message-ID: <176060833794.709179.12170959624692745095.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:52:17 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Petr Mladek <pmladek@...e.com>, Joe Lawrence <joe.lawrence@...hat.com>,
Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] objtool/klp: Add --debug-checksum=<funcs> to show
per-instruction checksums
The following commit has been merged into the objtool/core branch of tip:
Commit-ID: a3493b33384a01a1f0e38b420d1a4766aec903a6
Gitweb: https://git.kernel.org/tip/a3493b33384a01a1f0e38b420d1a4766aec903a6
Author: Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate: Wed, 17 Sep 2025 09:03:58 -07:00
Committer: Josh Poimboeuf <jpoimboe@...nel.org>
CommitterDate: Tue, 14 Oct 2025 14:50:18 -07:00
objtool/klp: Add --debug-checksum=<funcs> to show per-instruction checksums
Add a --debug-checksum=<funcs> option to the check subcommand to print
the calculated checksum of each instruction in the given functions.
This is useful for determining where two versions of a function begin to
diverge.
Acked-by: Petr Mladek <pmladek@...e.com>
Tested-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
tools/objtool/builtin-check.c | 6 +++-
tools/objtool/check.c | 42 +++++++++++++++++++++++-
tools/objtool/include/objtool/builtin.h | 1 +-
tools/objtool/include/objtool/checksum.h | 1 +-
tools/objtool/include/objtool/elf.h | 1 +-
tools/objtool/include/objtool/warn.h | 19 ++++++++++-
6 files changed, 70 insertions(+)
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 14daa13..7b6fd60 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -94,6 +94,7 @@ static const struct option check_options[] = {
OPT_GROUP("Options:"),
OPT_BOOLEAN(0, "backtrace", &opts.backtrace, "unwind on error"),
OPT_BOOLEAN(0, "backup", &opts.backup, "create backup (.orig) file on warning/error"),
+ 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_BOOLEAN(0, "link", &opts.link, "object is a linked object"),
OPT_BOOLEAN(0, "module", &opts.module, "object is part of a kernel module"),
@@ -168,6 +169,11 @@ static bool opts_valid(void)
}
#endif
+ if (opts.debug_checksum && !opts.checksum) {
+ ERROR("--debug-checksum requires --checksum");
+ return false;
+ }
+
if (opts.checksum ||
opts.hack_jump_label ||
opts.hack_noinstr ||
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f5adbd2..0f52781 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -3580,6 +3580,44 @@ static bool skip_alt_group(struct instruction *insn)
return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;
}
+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) {
+ struct symbol *func;
+ char *comma;
+
+ comma = strchr(s, ',');
+ if (comma)
+ *comma = '\0';
+
+ func = find_symbol_by_name(file->elf, s);
+ if (!func || !is_func_sym(func))
+ WARN("--debug-checksum: can't find '%s'", s);
+ else
+ func->debug_checksum = 1;
+
+ 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)
{
@@ -4818,6 +4856,10 @@ int check(struct objtool_file *file)
cfi_hash_add(&init_cfi);
cfi_hash_add(&func_cfi);
+ ret = checksum_debug_init(file);
+ if (ret)
+ goto out;
+
ret = decode_sections(file);
if (ret)
goto out;
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 338bdab..cee9fc0 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -32,6 +32,7 @@ struct opts {
/* options: */
bool backtrace;
bool backup;
+ const char *debug_checksum;
bool dryrun;
bool link;
bool mnop;
diff --git a/tools/objtool/include/objtool/checksum.h b/tools/objtool/include/objtool/checksum.h
index 927ca74..7fe2160 100644
--- a/tools/objtool/include/objtool/checksum.h
+++ b/tools/objtool/include/objtool/checksum.h
@@ -19,6 +19,7 @@ static inline void checksum_update(struct symbol *func,
const void *data, size_t size)
{
XXH3_64bits_update(func->csum.state, data, size);
+ dbg_checksum(func, insn, XXH3_64bits_digest(func->csum.state));
}
static inline void checksum_finish(struct symbol *func)
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index bc7d8a6..a1f1762 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -82,6 +82,7 @@ struct symbol {
u8 nocfi : 1;
u8 cold : 1;
u8 prefix : 1;
+ u8 debug_checksum : 1;
struct list_head pv_target;
struct reloc *relocs;
struct section *group_sec;
diff --git a/tools/objtool/include/objtool/warn.h b/tools/objtool/include/objtool/warn.h
index cb8fe84..29173a1 100644
--- a/tools/objtool/include/objtool/warn.h
+++ b/tools/objtool/include/objtool/warn.h
@@ -102,4 +102,23 @@ static inline char *offstr(struct section *sec, unsigned long offset)
#define ERROR_FUNC(sec, offset, format, ...) __WARN_FUNC(ERROR_STR, sec, offset, format, ##__VA_ARGS__)
#define ERROR_INSN(insn, format, ...) WARN_FUNC(insn->sec, insn->offset, format, ##__VA_ARGS__)
+
+#define __dbg(format, ...) \
+ fprintf(stderr, \
+ "DEBUG: %s%s" format "\n", \
+ objname ?: "", \
+ objname ? ": " : "", \
+ ##__VA_ARGS__)
+
+#define dbg_checksum(func, insn, checksum) \
+({ \
+ if (unlikely(insn->sym && insn->sym->pfunc && \
+ insn->sym->pfunc->debug_checksum)) { \
+ char *insn_off = offstr(insn->sec, insn->offset); \
+ __dbg("checksum: %s %s %016lx", \
+ func->name, insn_off, checksum); \
+ free(insn_off); \
+ } \
+})
+
#endif /* _WARN_H */
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