[tip: objtool/core] objtool: Add --output option

From: tip-bot2 for Josh Poimboeuf
Date: Mon Mar 17 2025 - 06:47:21 EST

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The following commit has been merged into the objtool/core branch of tip:

Commit-ID: 5a406031d0719d146d2033ee4270310b1ca9a1e3
Gitweb: https://git.kernel.org/tip/5a406031d0719d146d2033ee4270310b1ca9a1e3
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Fri, 14 Mar 2025 12:29:07 -07:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Mon, 17 Mar 2025 11:36:01 +01:00

objtool: Add --output option

Add option to allow writing the changed binary to a separate file rather
than changing it in place.

Libelf makes this suprisingly hard, so take the easy way out and just
copy the file before editing it.

Also steal the -o short option from --orc. Nobody will notice ;-)

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/0da308d42d82b3bbed16a31a72d6bde52afcd6bd.1741975349.git.jpoimboe@xxxxxxxxxx
---
tools/objtool/builtin-check.c | 98 +++++++++++++++++++-----
tools/objtool/elf.c | 3 +-
tools/objtool/include/objtool/builtin.h | 1 +-
tools/objtool/objtool.c | 15 +---
tools/objtool/orc_dump.c | 7 +--
5 files changed, 89 insertions(+), 35 deletions(-)

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 7984351..3de3afa 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -6,6 +6,10 @@
#include <subcmd/parse-options.h>
#include <string.h>
#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/sendfile.h>
#include <objtool/builtin.h>
#include <objtool/objtool.h>

@@ -14,6 +18,8 @@
"error: objtool: " format "\n", \
##__VA_ARGS__)

+const char *objname;
+
struct opts opts;

static const char * const check_usage[] = {
@@ -71,7 +77,7 @@ static const struct option check_options[] = {
OPT_BOOLEAN('i', "ibt", &opts.ibt, "validate and annotate IBT"),
OPT_BOOLEAN('m', "mcount", &opts.mcount, "annotate mcount/fentry calls for ftrace"),
OPT_BOOLEAN('n', "noinstr", &opts.noinstr, "validate noinstr rules"),
- OPT_BOOLEAN('o', "orc", &opts.orc, "generate ORC metadata"),
+ OPT_BOOLEAN(0, "orc", &opts.orc, "generate ORC metadata"),
OPT_BOOLEAN('r', "retpoline", &opts.retpoline, "validate and annotate retpoline usage"),
OPT_BOOLEAN(0, "rethunk", &opts.rethunk, "validate and annotate rethunk usage"),
OPT_BOOLEAN(0, "unret", &opts.unret, "validate entry unret placement"),
@@ -84,15 +90,16 @@ static const struct option check_options[] = {
OPT_CALLBACK_OPTARG(0, "dump", NULL, NULL, "orc", "dump metadata", parse_dump),

OPT_GROUP("Options:"),
- OPT_BOOLEAN(0, "backtrace", &opts.backtrace, "unwind on error"),
- OPT_BOOLEAN(0, "backup", &opts.backup, "create .orig files before modification"),
- 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"),
- OPT_BOOLEAN(0, "mnop", &opts.mnop, "nop out mcount call sites"),
- OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
- OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
- OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
+ OPT_BOOLEAN(0, "backtrace", &opts.backtrace, "unwind on error"),
+ OPT_BOOLEAN(0, "backup", &opts.backup, "create .orig files before modification"),
+ 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"),
+ OPT_BOOLEAN(0, "mnop", &opts.mnop, "nop out mcount call sites"),
+ OPT_BOOLEAN(0, "no-unreachable", &opts.no_unreachable, "skip 'unreachable instruction' warnings"),
+ OPT_STRING('o', "output", &opts.output, "file", "output file name"),
+ OPT_BOOLEAN(0, "sec-address", &opts.sec_address, "print section addresses in warnings"),
+ OPT_BOOLEAN(0, "stats", &opts.stats, "print statistics"),
OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),

OPT_END(),
@@ -178,24 +185,75 @@ static bool opts_valid(void)
return false;
}

+static int copy_file(const char *src, const char *dst)
+{
+ size_t to_copy, copied;
+ int dst_fd, src_fd;
+ struct stat stat;
+ off_t offset = 0;
+
+ src_fd = open(src, O_RDONLY);
+ if (src_fd == -1) {
+ ERROR("can't open '%s' for reading", src);
+ return 1;
+ }
+
+ dst_fd = open(dst, O_WRONLY | O_CREAT | O_TRUNC);
+ if (dst_fd == -1) {
+ ERROR("can't open '%s' for writing", dst);
+ return 1;
+ }
+
+ if (fstat(src_fd, &stat) == -1) {
+ perror("fstat");
+ return 1;
+ }
+
+ if (fchmod(dst_fd, stat.st_mode) == -1) {
+ perror("fchmod");
+ return 1;
+ }
+
+ for (to_copy = stat.st_size; to_copy > 0; to_copy -= copied) {
+ copied = sendfile(dst_fd, src_fd, &offset, to_copy);
+ if (copied == -1) {
+ perror("sendfile");
+ return 1;
+ }
+ }
+
+ close(dst_fd);
+ close(src_fd);
+ return 0;
+}
+
int objtool_run(int argc, const char **argv)
{
- const char *objname;
struct objtool_file *file;
int ret;

- argc = cmd_parse_options(argc, argv, check_usage);
- objname = argv[0];
+ cmd_parse_options(argc, argv, check_usage);

if (!opts_valid())
return 1;

+ objname = argv[0];
+
if (opts.dump_orc)
return orc_dump(objname);

+ if (!opts.dryrun && opts.output) {
+ /* copy original .o file to output file */
+ if (copy_file(objname, opts.output))
+ return 1;
+
+ /* from here on, work directly on the output file */
+ objname = opts.output;
+ }
+
file = objtool_open_read(objname);
if (!file)
- return 1;
+ goto err;

if (!opts.link && has_multiple_files(file->elf)) {
ERROR("Linked object requires --link");
@@ -204,10 +262,16 @@ int objtool_run(int argc, const char **argv)

ret = check(file);
if (ret)
- return ret;
+ goto err;

- if (file->elf->changed)
- return elf_write(file->elf);
+ if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
+ goto err;

return 0;
+
+err:
+ if (opts.output)
+ unlink(opts.output);
+
+ return 1;
}
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 6f64d61..be4f4b6 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -1302,9 +1302,6 @@ int elf_write(struct elf *elf)
struct section *sec;
Elf_Scn *s;

- if (opts.dryrun)
- return 0;
-
/* Update changed relocation sections and section headers: */
list_for_each_entry(sec, &elf->sections, list) {
if (sec->truncate)
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index fcca666..25cfa01 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -35,6 +35,7 @@ struct opts {
bool mnop;
bool module;
bool no_unreachable;
+ const char *output;
bool sec_address;
bool stats;
bool verbose;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index f40febd..53cd881 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -18,7 +18,6 @@

bool help;

-const char *objname;
static struct objtool_file file;

static bool objtool_create_backup(const char *_objname)
@@ -79,18 +78,14 @@ static bool objtool_create_backup(const char *_objname)
return true;
}

-struct objtool_file *objtool_open_read(const char *_objname)
+struct objtool_file *objtool_open_read(const char *filename)
{
- if (objname) {
- if (strcmp(objname, _objname)) {
- WARN("won't handle more than one file at a time");
- return NULL;
- }
- return &file;
+ if (file.elf) {
+ WARN("won't handle more than one file at a time");
+ return NULL;
}
- objname = _objname;

- file.elf = elf_open_read(objname, O_RDWR);
+ file.elf = elf_open_read(filename, O_RDWR);
if (!file.elf)
return NULL;

diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index a62247e..05ef0e2 100644
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -10,7 +10,7 @@
#include <objtool/warn.h>
#include <objtool/endianness.h>

-int orc_dump(const char *_objname)
+int orc_dump(const char *filename)
{
int fd, nr_entries, i, *orc_ip = NULL, orc_size = 0;
struct orc_entry *orc = NULL;
@@ -26,12 +26,9 @@ int orc_dump(const char *_objname)
Elf_Data *data, *symtab = NULL, *rela_orc_ip = NULL;
struct elf dummy_elf = {};

-
- objname = _objname;
-
elf_version(EV_CURRENT);

- fd = open(objname, O_RDONLY);
+ fd = open(filename, O_RDONLY);
if (fd == -1) {
perror("open");
return -1;

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