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objtool: Fix skip_alt_group() for non-alternative STAC/CLAC 

If an insn->alt points to a STAC/CLAC instruction, skip_alt_group()
assumes it's part of an alternative ("alt group") as opposed to some
other kind of "alt" such as an exception fixup.

While that assumption may hold true in the current code base, Linus has
an out-of-tree patch which breaks that assumption by replacing the
STAC/CLAC alternatives with raw STAC/CLAC instructions.

Make skip_alt_group() more robust by making sure it's actually an alt
group before continuing.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Fixes: 2d12c6fb78 ("objtool: Remove ANNOTATE_IGNORE_ALTERNATIVE from CLAC/STAC")
Closes: https://lore.kernel.org/CAHk-=wi6goUT36sR8GE47_P-aVrd5g38=VTRHpktWARbyE-0ow@mail.gmail.com
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://patch.msgid.link/3d22415f7b8e06a64e0873b21f48389290eeaa49.1761767616.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2025-10-29 12:54:08 -07:00 committed by Ingo Molnar
parent ba36dd5ee6
commit c44b4b9eeb
1 changed files with 4 additions and 1 deletions
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5
tools/objtool/check.c
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@ -3516,8 +3516,11 @@ static bool skip_alt_group(struct instruction *insn)
{
struct instruction *alt_insn = insn->alts ? insn->alts->insn : NULL;
if (!insn->alt_group)
return false;
/* ANNOTATE_IGNORE_ALTERNATIVE */
if (insn->alt_group && insn->alt_group->ignore)
if (insn->alt_group->ignore)
return true;
/*