[PATCH v3 03/39] objtool: Add --dry-run

Peter Zijlstra
2022-03-03T11:30:49Z

Add a --dry-run argument to skip writing the modifications. This is
convenient for debugging.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
---
tools/objtool/builtin-check.c | 3 ++-
tools/objtool/elf.c | 3 +++
tools/objtool/include/objtool/builtin.h | 2 +-
3 files changed, 6 insertions(+), 2 deletions(-)

--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -20,7 +20,7 @@
#include <objtool/objtool.h>

bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
- validate_dup, vmlinux, mcount, noinstr, backup, sls;
+ validate_dup, vmlinux, mcount, noinstr, backup, sls, dryrun;

static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -46,6 +46,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
OPT_BOOLEAN('B', "backup", &backup, "create .orig files before modification"),
OPT_BOOLEAN('S', "sls", &sls, "validate straight-line-speculation"),
+ OPT_BOOLEAN(0, "dry-run", &dryrun, "don't write the modifications"),
OPT_END(),
};

--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1019,6 +1019,9 @@ int elf_write(struct elf *elf)
struct section *sec;
Elf_Scn *s;

+ if (dryrun)
+ return 0;
+
/* Update changed relocation sections and section headers: */
list_for_each_entry(sec, &elf->sections, list) {
if (sec->changed) {
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -9,7 +9,7 @@

extern const struct option check_options[];
extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
- validate_dup, vmlinux, mcount, noinstr, backup, sls;
+ validate_dup, vmlinux, mcount, noinstr, backup, sls, dryrun;

extern int cmd_parse_options(int argc, const char **argv, const char * const usage[]);