[PATCH] objtool: Ignore dangling jump table entries

[PATCH] objtool: Ignore dangling jump table entries

[Josh Poimboeuf]

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

Reported-by: Klaus Kusche <klaus.kusche@computerix.info>
Closes: https://lore.kernel.org/20250113235835.vqgvb7cdspksy5dn@jpoimboe
Signed-off-by: Josh Poimboeuf <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 76060da755b5..4a0c5bb7e457 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);
 	}
 
-- 
2.47.1

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

[tip-bot2 for Josh Poimboeuf]

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@kernel.org>
AuthorDate:    Tue, 14 Jan 2025 13:57:58 -08:00
Committer:     Peter Zijlstra <peterz@infradead.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@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
---
 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);
 	}