[PATCH AUTOSEL 6.6 08/17] objtool: Ignore dangling jump table entries

Sasha Levin
2025-02-18T20:28:01Z

From: Josh Poimboeuf <jpoimboe@kernel.org>

[ Upstream commit 3724062ca2b1364f02cf44dbea1a552227844ad1 ]

Clang sometimes leaves dangling unused jump table entries which point to
the end of the function. Ignore them.

Closes: https://lore.kernel.org/20250113235835.vqgvb7cdspksy5dn@jpoimboe
Reported-by: Klaus Kusche <klaus.kusche@computerix.info>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/ee25c0b7e80113e950bd1d4c208b671d35774ff4.1736891751.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/objtool/check.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 1b242c3c2d451..6e59e7f578ffe 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2028,6 +2028,14 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
reloc_addend(reloc) == pfunc->offset)
break;

+ /*
+ * Clang sometimes leaves dangling unused jump table entries
+ * which point to the end of the function. Ignore them.
+ */
+ if (reloc->sym->sec == pfunc->sec &&
+ reloc_addend(reloc) == pfunc->offset + pfunc->len)
+ goto next;
+
dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
if (!dest_insn)
break;
@@ -2045,6 +2053,7 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
alt->insn = dest_insn;
alt->next = insn->alts;
insn->alts = alt;
+next:
prev_offset = reloc_offset(reloc);
}

--
2.39.5