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objtool/x86: Fixup frame-pointer vs rethunk

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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: 4ae68b26c3 ("objtool/x86: Fix SRSO mess")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230816115921.GH980931@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra 2023-08-16 13:59:21 +02:00 committed by Borislav Petkov (AMD)
parent 9dbd23e42f
commit dbf4600877
1 changed files with 11 additions and 6 deletions
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17
tools/objtool/check.c
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@ -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)
return true;
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;