Commit 55eeab2a authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Ignore exc_double_fault() __noreturn warnings 



This is a hack, but it works for now.

Problem is, exc_double_fault() may or may not return, depending on
whether CONFIG_X86_ESPFIX64 is set.  But objtool has no visibility to
the kernel config.

"Fix" it by silencing the exc_double_fault() __noreturn warning.

This removes the following warning:

  vmlinux.o: warning: objtool: xenpv_exc_double_fault+0xd: exc_double_fault() is missing a __noreturn annotation

Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Link: https://lore.kernel.org/r/a45b085071d3a7d049a20f9e78754452336ecbe8.1681853186.git.jpoimboe@kernel.org


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent fedb724c

tools/objtool/check.c

+30 −1
Original line number Diff line number Diff line
@@ -4505,6 +4505,35 @@ static int validate_sls(struct objtool_file *file) 
	return warnings;

}



static bool ignore_noreturn_call(struct instruction *insn)

{

	struct symbol *call_dest = insn_call_dest(insn);



	/*

	 * FIXME: hack, we need a real noreturn solution

	 *

	 * Problem is, exc_double_fault() may or may not return, depending on

	 * whether CONFIG_X86_ESPFIX64 is set.  But objtool has no visibility

	 * to the kernel config.

	 *

	 * Other potential ways to fix it:

	 *

	 *   - have compiler communicate __noreturn functions somehow

	 *   - remove CONFIG_X86_ESPFIX64

	 *   - read the .config file

	 *   - add a cmdline option

	 *   - create a generic objtool annotation format (vs a bunch of custom

	 *     formats) and annotate it

	 */

	if (!strcmp(call_dest->name, "exc_double_fault")) {

		/* prevent further unreachable warnings for the caller */

		insn->sym->warned = 1;

		return true;

	}



	return false;

}



static int validate_reachable_instructions(struct objtool_file *file)

{

	struct instruction *insn, *prev_insn;
@@ -4521,7 +4550,7 @@ static int validate_reachable_instructions(struct objtool_file *file) 
		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) {

			if (call_dest && !ignore_noreturn_call(prev_insn)) {

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

					  call_dest->name);

				warnings++;