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objtool: Fix UNWIND_HINT_{SAVE,RESTORE} across basic blocks

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If SAVE and RESTORE unwind hints are in different basic blocks, and
objtool sees the RESTORE before the SAVE, it errors out with:

  vmlinux.o: warning: objtool: vmw_port_hb_in+0x242: objtool isn't smart enough to handle this CFI save/restore combo

In such a case, defer following the RESTORE block until the
straight-line path gets followed later.

Fixes: 8faea26e6111 ("objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402240702.zJFNmahW-lkp@intel.com/
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20240227073527.avcm5naavbv3cj5s@treble
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Josh Poimboeuf 2024-02-26 23:35:27 -08:00 committed by Kees Cook
parent c5e6d3d85e
commit 10b4c4bce3
1 changed files with 12 additions and 0 deletions
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12
tools/objtool/check.c
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@ -3620,6 +3620,18 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
}
if (!save_insn->visited) {
/*
* If the restore hint insn is at the
* beginning of a basic block and was
* branched to from elsewhere, and the
* save insn hasn't been visited yet,
* defer following this branch for now.
* It will be seen later via the
* straight-line path.
*/
if (!prev_insn)
return 0;
WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
return 1;
}