[PATCH 4/5] objtool: Fix switch table detection in .text.unlikely

Josh Poimboeuf
2020-04-01T18:23:55Z

If a switch jump table's indirect branch is in a ".cold" subfunction in
.text.unlikely, objtool doesn't detect it, and instead prints a false
warning:

drivers/media/v4l2-core/v4l2-ioctl.o: warning: objtool: v4l_print_format.cold()+0xd6: sibling call from callable instruction with modified stack frame
drivers/hwmon/max6650.o: warning: objtool: max6650_probe.cold()+0xa5: sibling call from callable instruction with modified stack frame
drivers/media/dvb-frontends/drxk_hard.o: warning: objtool: init_drxk.cold()+0x16f: sibling call from callable instruction with modified stack frame

Fix it by comparing the function, instead of the section and offset.

Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
tools/objtool/check.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index aaec5e1277ea..c681a26c25ac 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1068,10 +1068,7 @@ static struct rela *find_jump_table(struct objtool_file *file,
* it.
*/
for (;
- &insn->list != &file->insn_list &&
- insn->sec == func->sec &&
- insn->offset >= func->offset;
-
+ &insn->list != &file->insn_list && insn->func && insn->func->pfunc == func;
insn = insn->first_jump_src ?: list_prev_entry(insn, list)) {

if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
--
2.21.1