This is a note to let you know that I've just added the patch titled
objtool: Fix UNWIND_HINT_{SAVE,RESTORE} across basic blocks
to the 6.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
objtool-fix-unwind_hint_-save-restore-across-basic-b.patch
and it can be found in the queue-6.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit bb4e1a6e37e7d0698d3341d3db574fd9ff0e9564
Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Date: Mon Feb 26 23:35:27 2024 -0800
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: 8faea26e6111 ("objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}")
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202402240702.zJFNmahW-lkp@xxxxxxxxx/
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240227073527.avcm5naavbv3cj5s@treble
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 548ec3cd7c00c..c4c2f75eadfd9 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -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;
}
