objtool: Fix UNWIND_HINT_{SAVE,RESTORE} across basic blocks
[ Upstream commit 10b4c4bce3f5541f54bcc2039720b11d2bc96d79 ]
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: 8faea26e61
("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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@ -3604,6 +3604,18 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
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}
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if (!save_insn->visited) {
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/*
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* If the restore hint insn is at the
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* beginning of a basic block and was
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* branched to from elsewhere, and the
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* save insn hasn't been visited yet,
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* defer following this branch for now.
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* It will be seen later via the
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* straight-line path.
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*/
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if (!prev_insn)
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return 0;
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WARN_INSN(insn, "objtool isn't smart enough to handle this CFI save/restore combo");
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return 1;
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}
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