[tip: objtool/core] objtool/klp: Add test for rejecting module-owned static branch keys

[tip-bot2 for Puranjay Mohan]

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

Commit-ID:     7be49a35ce975ef9f2ccf3aa0dc4cf92ce244918
Gitweb:        https://git.kernel.org/tip/7be49a35ce975ef9f2ccf3aa0dc4cf92ce244918
Author:        Puranjay Mohan <puranjay@xxxxxxxxxx>
AuthorDate:    Wed, 16 Sep 2026 11:43:13 -07:00
Committer:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
CommitterDate: Wed, 16 Sep 2026 17:13:27 -07:00

objtool/klp: Add test for rejecting module-owned static branch keys

A static branch key belonging to a module cannot be reached with a klp
relocation: the patch may be applied after that module's static branch init
has run, which corrupts the code.  Emitting one anyway produces a module
which loads and then BUG()s the first time the key changes state, so klp
diff has to refuse it.

The fixture differs from the accepted case only in the module name recorded
in .modinfo.

Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Link: https://patch.msgid.link/20260916184351.2720310-21-song@xxxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/tests/generic/test-jump-label-module-key.sh | 22 +++++++-
 1 file changed, 22 insertions(+)
 create mode 100755 tools/objtool/tests/generic/test-jump-label-module-key.sh

diff --git a/tools/objtool/tests/generic/test-jump-label-module-key.sh b/tools/objtool/tests/generic/test-jump-label-module-key.sh
new file mode 100755
index 0000000..7c3f82c
--- /dev/null
+++ b/tools/objtool/tests/generic/test-jump-label-module-key.sh
@@ -0,0 +1,22 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# A static branch key owned by a module cannot be reached with a klp
+# relocation and must be rejected.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+build_pair jump_label.c -DMODNAME='"klp_testmod"'
+
+has_input_section orig.o __jump_table ||
+	probe_skip "fixture produced no __jump_table on this arch"
+
+run_diff 255
+
+diff_log | grep -q 'unsupported static branch key klp_test_key' ||
+	fail "expected rejection, got: $(diff_log | tail -1)"
+[ -e "$workdir/out.o" ] &&
+	fail "output object produced for a rejected input"
+
+pass "module-owned static branch key rejected"