Commit fedb724c authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Detect missing __noreturn annotations 



Most "unreachable instruction" warnings these days seem to actually be
the result of a missing __noreturn annotation.  Add an explicit check
for that.

Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/6e2b93d8c65eaed6c4166a358269dc0ef01f890c.1681853186.git.jpoimboe@kernel.org


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent ced23d2e

tools/objtool/Documentation/objtool.txt

+6 −0
Original line number Diff line number Diff line
@@ -303,6 +303,12 @@ the objtool maintainers. 
   If it's not actually in a callable function (e.g. kernel entry code),

   change ENDPROC to END.



3. file.o: warning: objtool: foo+0x48c: bar() is missing a __noreturn annotation



   The call from foo() to bar() doesn't return, but bar() is missing the

   __noreturn annotation.  NOTE: In addition to adding the __noreturn

   annotation, the function name also needs to be added to

   'global_noreturns' in tools/objtool/check.c.



4. file.o: warning: objtool: func(): can't find starting instruction

   or

tools/objtool/check.c

+13 −1
Original line number Diff line number Diff line
@@ -4507,7 +4507,8 @@ static int validate_sls(struct objtool_file *file) 


static int validate_reachable_instructions(struct objtool_file *file)

{

	struct instruction *insn;

	struct instruction *insn, *prev_insn;

	struct symbol *call_dest;

	int warnings = 0;



	if (file->ignore_unreachables)
@@ -4517,6 +4518,17 @@ static int validate_reachable_instructions(struct objtool_file *file) 
		if (insn->visited || ignore_unreachable_insn(file, insn))

			continue;



		prev_insn = prev_insn_same_sec(file, insn);

		if (prev_insn && prev_insn->dead_end) {

			call_dest = insn_call_dest(prev_insn);

			if (call_dest) {

				WARN_INSN(insn, "%s() is missing a __noreturn annotation",

					  call_dest->name);

				warnings++;

				continue;

			}

		}



		WARN_INSN(insn, "unreachable instruction");

		warnings++;

	}