Commit 0e5b613b authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Rework ASM_REACHABLE 



Currently ASM_REACHABLE only works for UD2 instructions; reorder
things to also allow over-riding dead_end_function().

To that end:

 - Mark INSN_BUG instructions in decode_instructions(), this saves
   having to iterate all instructions yet again.

 - Have add_call_destinations() set insn->dead_end for
   dead_end_function() calls.

 - Move add_dead_ends() *after* add_call_destinations() such that
   ASM_REACHABLE can clear the ->dead_end mark.

 - have validate_branch() only check ->dead_end.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.410010807@infradead.org
parent 105cd685

tools/objtool/check.c

+20 −13
Original line number Diff line number Diff line
@@ -395,6 +395,14 @@ static int decode_instructions(struct objtool_file *file) 
			if (ret)

				goto err;



			/*

			 * By default, "ud2" is a dead end unless otherwise

			 * annotated, because GCC 7 inserts it for certain

			 * divide-by-zero cases.

			 */

			if (insn->type == INSN_BUG)

				insn->dead_end = true;



			hash_add(file->insn_hash, &insn->hash, sec_offset_hash(sec, insn->offset));

			list_add_tail(&insn->list, &file->insn_list);

			nr_insns++;
@@ -523,14 +531,6 @@ static int add_dead_ends(struct objtool_file *file) 
	struct reloc *reloc;

	struct instruction *insn;



	/*

	 * By default, "ud2" is a dead end unless otherwise annotated, because

	 * GCC 7 inserts it for certain divide-by-zero cases.

	 */

	for_each_insn(file, insn)

		if (insn->type == INSN_BUG)

			insn->dead_end = true;



	/*

	 * Check for manually annotated dead ends.

	 */
@@ -1114,6 +1114,9 @@ static void annotate_call_site(struct objtool_file *file, 
		list_add_tail(&insn->call_node, &file->mcount_loc_list);

		return;

	}



	if (!sibling && dead_end_function(file, sym))

		insn->dead_end = true;

}



static void add_call_dest(struct objtool_file *file, struct instruction *insn,
@@ -2089,10 +2092,6 @@ static int decode_sections(struct objtool_file *file) 
	if (ret)

		return ret;



	ret = add_dead_ends(file);

	if (ret)

		return ret;



	add_ignores(file);

	add_uaccess_safe(file);
@@ -2131,6 +2130,14 @@ static int decode_sections(struct objtool_file *file) 
	if (ret)

		return ret;



	/*

	 * Must be after add_call_destinations() such that it can override

	 * dead_end_function() marks.

	 */

	ret = add_dead_ends(file);

	if (ret)

		return ret;



	ret = add_jump_table_alts(file);

	if (ret)

		return ret;
@@ -3138,7 +3145,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 
				return 1;

			}



			if (dead_end_function(file, insn->call_dest))

			if (insn->dead_end)

				return 0;



			break;