Commit dbf46008 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Borislav Petkov (AMD)
Browse files

objtool/x86: Fixup frame-pointer vs rethunk 



For stack-validation of a frame-pointer build, objtool validates that
every CALL instruction is preceded by a frame-setup. The new SRSO
return thunks violate this with their RSB stuffing trickery.

Extend the __fentry__ exception to also cover the embedded_insn case
used for this. This cures:

  vmlinux.o: warning: objtool: srso_untrain_ret+0xd: call without frame pointer save/setup

Fixes: 4ae68b26 ("objtool/x86: Fix SRSO mess")
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230816115921.GH980931@hirez.programming.kicks-ass.net
parent 9dbd23e4

tools/objtool/check.c

+11 −6
Original line number Diff line number Diff line
@@ -2650,12 +2650,17 @@ static int decode_sections(struct objtool_file *file) 
	return 0;

}



static bool is_fentry_call(struct instruction *insn)

static bool is_special_call(struct instruction *insn)

{

	if (insn->type == INSN_CALL &&

	    insn_call_dest(insn) &&

	    insn_call_dest(insn)->fentry)

	if (insn->type == INSN_CALL) {

		struct symbol *dest = insn_call_dest(insn);



		if (!dest)

			return false;



		if (dest->fentry || dest->embedded_insn)

			return true;

	}



	return false;

}
@@ -3656,7 +3661,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 
			if (ret)

				return ret;



			if (opts.stackval && func && !is_fentry_call(insn) &&

			if (opts.stackval && func && !is_special_call(insn) &&

			    !has_valid_stack_frame(&state)) {

				WARN_INSN(insn, "call without frame pointer save/setup");

				return 1;