linux-kernel - Re: [PATCH v2 32/62] objtool: Suppress section skipping warnings with --dryrun

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Message-ID: <20250605145224.GE35970@noisy.programming.kicks-ass.net>
Date: Thu, 5 Jun 2025 16:52:24 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 32/62] objtool: Suppress section skipping warnings
 with --dryrun

On Thu, Jun 05, 2025 at 09:32:46AM +0200, Peter Zijlstra wrote:

> > But also, feel free to resurrect --backup, or you can yell at me to do
> > it as the backup code changed a bit.
> 
> I have the patch somewhere, failed to send it out. I'll try and dig it
> out later today.

This is what I had. Wasn't sure we wanted to make -v imply --backup ?

I'm used to stealing the objtool arguments from V=1 builds. I suppose
the print_args thing is easier, might get used to it eventually.


diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 80239843e9f0..7d8f99cf9b0b 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -101,6 +101,7 @@ static const struct option check_options[] = {
 	OPT_BOOLEAN(0,   "stats", &opts.stats, "print statistics"),
 	OPT_BOOLEAN('v', "verbose", &opts.verbose, "verbose warnings"),
 	OPT_BOOLEAN(0,   "Werror", &opts.werror, "return error on warnings"),
+	OPT_BOOLEAN(0,   "backup", &opts.backup, "create a backup (.orig) file on error"),
 
 	OPT_END(),
 };
@@ -244,13 +245,10 @@ static void save_argv(int argc, const char **argv)
 	};
 }
 
-void print_args(void)
+static void make_backup(void)
 {
 	char *backup = NULL;
 
-	if (opts.output || opts.dryrun)
-		goto print;
-
 	/*
 	 * Make a backup before kbuild deletes the file so the error
 	 * can be recreated without recompiling or relinking.
@@ -258,17 +256,19 @@ void print_args(void)
 	backup = malloc(strlen(objname) + strlen(ORIG_SUFFIX) + 1);
 	if (!backup) {
 		ERROR_GLIBC("malloc");
-		goto print;
+		return;
 	}
 
 	strcpy(backup, objname);
 	strcat(backup, ORIG_SUFFIX);
 	if (copy_file(objname, backup)) {
 		backup = NULL;
-		goto print;
+		return;
 	}
+}
 
-print:
+void print_args(void)
+{
 	/*
 	 * Print the cmdline args to make it easier to recreate.  If '--output'
 	 * wasn't used, add it to the printed args with the backup as input.
@@ -278,10 +278,7 @@ void print_args(void)
 	for (int i = 1; i < orig_argc; i++) {
 		char *arg = orig_argv[i];
 
-		if (backup && !strcmp(arg, objname))
-			fprintf(stderr, " %s -o %s", backup, objname);
-		else
-			fprintf(stderr, " %s", arg);
+		fprintf(stderr, " %s", arg);
 	}
 
 	fprintf(stderr, "\n");
@@ -324,8 +321,11 @@ int objtool_run(int argc, const char **argv)
 	}
 
 	ret = check(file);
-	if (ret)
+	if (ret) {
+		if (opts.backup)
+			make_backup();
 		return ret;
+	}
 
 	if (!opts.dryrun && file->elf->changed && elf_write(file->elf))
 		return 1;
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index 6b08666fa69d..97c36fb1fe9a 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -39,6 +39,7 @@ struct opts {
 	bool stats;
 	bool verbose;
 	bool werror;
+	bool backup;
 };
 
 extern struct opts opts;