objtool/klp: Add test for newly introduced data

Adding data differs from changing it: nothing in the running kernel refers
to a new variable, so it is safe and has to travel into the livepatch with
the function using it.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Assisted-by: Claude:claude-opus-5
Link: https://patch.msgid.link/20260916184351.2720310-14-song@kernel.org

2 files changed, 50 insertions, 0 deletions

diff --git a/tools/objtool/tests/generic/fixtures/new_data.c b/tools/objtool/tests/generic/fixtures/new_data.c
new file mode 100644
index 000000000000..ac364622f12a
--- /dev/null
+++ b/tools/objtool/tests/generic/fixtures/new_data.c
@@ -0,0 +1,23 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Data introduced by the patch. */
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+#ifdef PATCHED
+/*
+ * Not an arithmetic progression: { 1, 2, 3, 4 } indexed by x & 3 is something
+ * a compiler can compute instead of load, and then target() has no reference
+ * to the array and there is nothing for klp diff to carry.
+ */
+static const int klp_new_data[4] __attribute__((used)) = { 7, 3, 11, 5 };
+#endif
+
+int target(int x)
+{
+#ifdef PATCHED
+	return x + klp_new_data[x & 3];
+#else
+	return x;
+#endif
+}
diff --git a/tools/objtool/tests/generic/test-new-data.sh b/tools/objtool/tests/generic/test-new-data.sh
new file mode 100755
index 000000000000..acb68ff19c99
--- /dev/null
+++ b/tools/objtool/tests/generic/test-new-data.sh
@@ -0,0 +1,27 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Data added by the patch has no counterpart in the running kernel and must be
+# carried into the livepatch.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+build_pair new_data.c
+
+# State the premise on both sides.  The array is new in the patched build and
+# absent from the original; if the compiler folded it into the code instead of
+# emitting it, the assertion below would fail without saying why.
+has_input_symbol "$orig_obj" klp_new_data &&
+	fail "fixture put klp_new_data in the original; nothing new to carry"
+has_input_symbol "$patched_obj" klp_new_data ||
+	fail "compiler did not emit klp_new_data; the fixture tests nothing"
+in_relocs "$patched_obj" | grep -q 'klp_new_data' ||
+	fail "target() does not reference klp_new_data; the fixture tests nothing"
+
+run_diff
+
+assert_patched target
+assert_symbol klp_new_data
+
+pass "new data carried into the patch"