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Date: Tue, 2 Mar 2021 12:58:37 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Borislav Petkov <bp@...en8.de>
Cc: jpoimboe@...hat.com, mbenes@...e.cz, linux-kernel@...r.kernel.org,
x86@...nel.org
Subject: Re: [PATCH 1/3] objtool: Add --backup
On Fri, Feb 26, 2021 at 12:48:19PM +0100, Borislav Petkov wrote:
> Yah, as mentioned on IRC and let me paste it here too, you need to
> supply mode with O_CREAT:
>
> d = open(name, O_CREAT|O_RDWR|O_TRUNC,S_IRUSR);
>
> or so. Also you could add perror("open") to those error paths so that it
> can say why it failed creating the backup file.
Patch now reads like:
---
Subject: objtool: Add --backup
From: Peter Zijlstra <peterz@...radead.org>
Date: Fri Feb 26 10:59:59 CET 2021
Teach objtool to write backups files, such that it becomes easier to
see what objtool did to the object file.
Backup files will be ${name}bj, such that file.o becomes file.obj.
Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Borislav Petkov <bp@...e.de>
---
tools/objtool/builtin-check.c | 4 +-
tools/objtool/include/objtool/builtin.h | 3 +
tools/objtool/objtool.c | 64 ++++++++++++++++++++++++++++++++
3 files changed, 69 insertions(+), 2 deletions(-)
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -18,7 +18,8 @@
#include <objtool/builtin.h>
#include <objtool/objtool.h>
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount, noinstr;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
+ validate_dup, vmlinux, mcount, noinstr, backup;
static const char * const check_usage[] = {
"objtool check [<options>] file.o",
@@ -37,6 +38,7 @@ const struct option check_options[] = {
OPT_BOOLEAN('n', "noinstr", &noinstr, "noinstr validation for vmlinux.o"),
OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"),
OPT_BOOLEAN('M', "mcount", &mcount, "generate __mcount_loc"),
+ OPT_BOOLEAN('B', "backup", &backup, "create .obj files before modification"),
OPT_END(),
};
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -8,7 +8,8 @@
#include <subcmd/parse-options.h>
extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux, mcount, noinstr;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats,
+ validate_dup, vmlinux, mcount, noinstr, backup;
extern int cmd_check(int argc, const char **argv);
extern int cmd_orc(int argc, const char **argv);
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -17,6 +17,7 @@
#include <stdbool.h>
#include <string.h>
#include <stdlib.h>
+#include <unistd.h>
#include <subcmd/exec-cmd.h>
#include <subcmd/pager.h>
#include <linux/kernel.h>
@@ -44,6 +45,64 @@ bool help;
const char *objname;
static struct objtool_file file;
+static bool objtool_create_backup(const char *_objname)
+{
+ int len = strlen(_objname);
+ char *buf, *base, *name = malloc(len+3);
+ int s, d, l, t;
+
+ if (!name) {
+ perror("failed backup name malloc");
+ return false;
+ }
+
+ strcpy(name, _objname);
+ strcpy(name + len, "bj");
+
+ d = open(name, O_CREAT|O_WRONLY|O_TRUNC, 0644);
+ if (d < 0) {
+ perror("failed to create backup file");
+ return false;
+ }
+
+ s = open(_objname, O_RDONLY);
+ if (s < 0) {
+ perror("failed to open orig file");
+ return false;
+ }
+
+ buf = malloc(4096);
+ if (!buf) {
+ perror("failed backup data malloc");
+ return false;
+ }
+
+ while ((l = read(s, buf, 4096)) > 0) {
+ base = buf;
+ do {
+ t = write(d, base, l);
+ if (t < 0) {
+ perror("failed backup write");
+ return false;
+ }
+ base += t;
+ l -= t;
+ } while (l);
+ }
+
+ if (l < 0) {
+ perror("failed backup read");
+ return false;
+ }
+
+ free(name);
+ free(buf);
+ close(d);
+ close(s);
+
+ return true;
+}
+
struct objtool_file *objtool_open_read(const char *_objname)
{
if (objname) {
@@ -59,6 +118,11 @@ struct objtool_file *objtool_open_read(c
if (!file.elf)
return NULL;
+ if (backup && !objtool_create_backup(objname)) {
+ WARN("can't create backup file");
+ return NULL;
+ }
+
INIT_LIST_HEAD(&file.insn_list);
hash_init(file.insn_hash);
INIT_LIST_HEAD(&file.static_call_list);
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