linux-kernel - [tip: objtool/urgent] objtool: Ignore dangling jump table entries

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Message-ID: <173902631974.10177.18265129202576943581.tip-bot2@tip-bot2>
Date: Sat, 08 Feb 2025 14:51:59 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Klaus Kusche <klaus.kusche@...puterix.info>,
 Josh Poimboeuf <jpoimboe@...nel.org>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: objtool/urgent] objtool: Ignore dangling jump table entries

The following commit has been merged into the objtool/urgent branch of tip:

Commit-ID:     3724062ca2b1364f02cf44dbea1a552227844ad1
Gitweb:        https://git.kernel.org/tip/3724062ca2b1364f02cf44dbea1a552227844ad1
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Tue, 14 Jan 2025 13:57:58 -08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Sat, 08 Feb 2025 15:43:08 +01:00

objtool: Ignore dangling jump table entries

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
---
 tools/objtool/check.c |  9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 753dbc4..3520a45 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1975,6 +1975,14 @@ 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;
@@ -1992,6 +2000,7 @@ 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);
 	}