objtool: Make jump label hack optional

Objtool secretly does a jump label hack to overcome the limitations of
the toolchain.  Make the hack explicit (and optional for other arches)
by turning it into a cmdline option and kernel config option.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/3bdcbfdd27ecb01ddec13c04bdf756a583b13d24.1650300597.git.jpoimboe@redhat.com

3 files changed, 31 insertions, 9 deletions

diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index c8c4d2bab42f..b2c626d9e2bf 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -31,8 +31,28 @@ static int parse_dump(const struct option *opt, const char *str, int unset)
 	return -1;
 }
 
+static int parse_hacks(const struct option *opt, const char *str, int unset)
+{
+	bool found = false;
+
+	/*
+	 * Use strstr() as a lazy method of checking for comma-separated
+	 * options.
+	 *
+	 * No string provided == enable all options.
+	 */
+
+	if (!str || strstr(str, "jump_label")) {
+		opts.hack_jump_label = true;
+		found = true;
+	}
+
+	return found ? 0 : -1;
+}
+
 const struct option check_options[] = {
 	OPT_GROUP("Actions:"),
+	OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label", "patch toolchain bugs/limitations", parse_hacks),
 	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"),
@@ -87,14 +107,15 @@ int cmd_parse_options(int argc, const char **argv, const char * const usage[])
 
 static bool opts_valid(void)
 {
-	if (opts.ibt		||
-	    opts.mcount		||
-	    opts.noinstr	||
-	    opts.orc		||
-	    opts.retpoline	||
-	    opts.sls		||
-	    opts.stackval	||
-	    opts.static_call	||
+	if (opts.hack_jump_label	||
+	    opts.ibt			||
+	    opts.mcount			||
+	    opts.noinstr		||
+	    opts.orc			||
+	    opts.retpoline		||
+	    opts.sls			||
+	    opts.stackval		||
+	    opts.static_call		||
 	    opts.uaccess) {
 		if (opts.dump_orc) {
 			fprintf(stderr, "--dump can't be combined with other options\n");
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index b9ac351ea08b..d157978c58b3 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1592,7 +1592,7 @@ static int handle_jump_alt(struct objtool_file *file,
 		return -1;
 	}
 
-	if (special_alt->key_addend & 2) {
+	if (opts.hack_jump_label && special_alt->key_addend & 2) {
 		struct reloc *reloc = insn_reloc(file, orig_insn);
 
 		if (reloc) {
diff --git a/tools/objtool/include/objtool/builtin.h b/tools/objtool/include/objtool/builtin.h
index dc4757205b8d..c6acf05ec859 100644
--- a/tools/objtool/include/objtool/builtin.h
+++ b/tools/objtool/include/objtool/builtin.h
@@ -12,6 +12,7 @@ extern const struct option check_options[];
 struct opts {
 	/* actions: */
 	bool dump_orc;
+	bool hack_jump_label;
 	bool ibt;
 	bool mcount;
 	bool noinstr;