Commit 34c861e8 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Peter Zijlstra
Browse files

objtool: Fix sibling call detection in alternatives 



In add_jump_destinations(), sibling call detection requires 'insn->func'
to be valid.  But alternative instructions get their 'func' set in
handle_group_alt(), which runs *after* add_jump_destinations().  So
sibling calls in alternatives code don't get properly detected.

Fix that by changing the initialization order: call
add_special_section_alts() *before* add_jump_destinations().

This also means the special case for a missing 'jump_dest' in
add_jump_destinations() can be removed, as it has already been dealt
with.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/c02e0a0a2a4286b5f848d17c77fdcb7e0caf709c.1649718562.git.jpoimboe@redhat.com
parent 26ff6041

tools/objtool/check.c

+17 −19
Original line number Diff line number Diff line
@@ -1277,6 +1277,13 @@ static int add_jump_destinations(struct objtool_file *file) 
	unsigned long dest_off;



	for_each_insn(file, insn) {

		if (insn->jump_dest) {

			/*

			 * handle_group_alt() may have previously set

			 * 'jump_dest' for some alternatives.

			 */

			continue;

		}

		if (!is_static_jump(insn))

			continue;
@@ -1308,15 +1315,6 @@ static int add_jump_destinations(struct objtool_file *file) 


		jump_dest = find_insn(file, dest_sec, dest_off);

		if (!jump_dest) {



			/*

			 * This is a special case where an alt instruction

			 * jumps past the end of the section.  These are

			 * handled later in handle_group_alt().

			 */

			if (!strcmp(insn->sec->name, ".altinstr_replacement"))

				continue;



			WARN_FUNC("can't find jump dest instruction at %s+0x%lx",

				  insn->sec, insn->offset, dest_sec->name,

				  dest_off);
@@ -1549,15 +1547,15 @@ static int handle_group_alt(struct objtool_file *file, 
			continue;



		dest_off = arch_jump_destination(insn);

		if (dest_off == special_alt->new_off + special_alt->new_len)

		if (dest_off == special_alt->new_off + special_alt->new_len) {

			insn->jump_dest = next_insn_same_sec(file, last_orig_insn);



			if (!insn->jump_dest) {

				WARN_FUNC("can't find alternative jump destination",

					  insn->sec, insn->offset);

				return -1;

			}

		}

	}



	if (!last_new_insn) {

		WARN_FUNC("can't find last new alternative instruction",
@@ -2254,14 +2252,14 @@ static int decode_sections(struct objtool_file *file) 
		return ret;



	/*

	 * Must be before add_special_section_alts() as that depends on

	 * jump_dest being set.

	 * Must be before add_jump_destinations(), which depends on 'func'

	 * being set for alternatives, to enable proper sibling call detection.

	 */

	ret = add_jump_destinations(file);

	ret = add_special_section_alts(file);

	if (ret)

		return ret;



	ret = add_special_section_alts(file);

	ret = add_jump_destinations(file);

	if (ret)

		return ret;