linux-kernel - [PATCH AUTOSEL 6.12 13/31] objtool: Ignore dangling jump table entries

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Message-Id: <20250218202619.3592630-13-sashal@kernel.org>
Date: Tue, 18 Feb 2025 15:25:59 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Josh Poimboeuf <jpoimboe@...nel.org>,
	Klaus Kusche <klaus.kusche@...puterix.info>,
	Peter Zijlstra <peterz@...radead.org>,
	Sasha Levin <sashal@...nel.org>,
	nathan@...nel.org,
	llvm@...ts.linux.dev
Subject: [PATCH AUTOSEL 6.12 13/31] objtool: Ignore dangling jump table entries

From: Josh Poimboeuf <jpoimboe@...nel.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@...puterix.info>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/ee25c0b7e80113e950bd1d4c208b671d35774ff4.1736891751.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/objtool/check.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f0d8796b984a8..34b1c16d359c9 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2099,6 +2099,14 @@ 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;
@@ -2116,6 +2124,7 @@ 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