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

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 753dbc4f81985368dd2b6b7ff580f3c329ef9763..3520a45ebde8b408af1f00ec0d2bc069e0be6842 100644 (file)
--- 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);
        }