[PATCH v3 11/15] objtool: Remove too strict constraint in jump table search

From: Christophe Leroy
Date: Fri Jun 23 2023 - 13:06:58 EST


In code there is often a pattern like:

load jump table address
do some test
conditional jump to label1:
do something
unconditional jump to label2:
label1:
do something else
read jump table
dynamic jump
label2:
do other job here ....

find_jump_table() contains a constraint that stops the backsearch
of the table address loading when a jump is found in-between.

Remove that constraint.

Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
tools/objtool/check.c | 7 -------
1 file changed, 7 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 05d789e6d3b6..c9f0fd31d146 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2067,13 +2067,6 @@ static struct reloc *find_jump_table(struct objtool_file *file,
if (insn != orig_insn && insn->type == INSN_JUMP_DYNAMIC)
break;

- /* allow small jumps within the range */
- if (insn->type == INSN_JUMP_UNCONDITIONAL &&
- insn->jump_dest &&
- (insn->jump_dest->offset <= insn->offset ||
- insn->jump_dest->offset > orig_insn->offset))
- break;
-
table_reloc = arch_find_switch_table(file, insn);
if (!table_reloc)
continue;
--
2.40.1