[PATCH v2 23/58] objtool/klp: Add test for rejecting references to init code/data

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Patched function referencing data in an .init section. */
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+static int init_only __attribute__((section(".init.data"), used)) = 5;
+
+int target(int x)
+{
+#ifdef PATCHED
+	return x + init_only + 1;
+#else
+	return x + init_only;
+#endif
+}

@@ -0,0 +1,27 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Init code and data are freed after boot, so a klp relocation against them can
+# never resolve.  Such a patch must be rejected.
+
+. "$(dirname "$0")/../lib.sh"
+
+setup
+build_pair init_reference.c
+
+# The rejection can only happen if the patched build really does reference the
+# init symbol.  Were the compiler to fold the read into a constant there would
+# be no relocation, klp diff would succeed, and the failure below would look
+# like a missing check rather than a fixture which stopped posing the question.
+# The reference is relocated against the section symbol rather than against
+# init_only, since the variable is file-local -- which is the form klp diff
+# has to recognise anyway.
+in_relocs "$patched_obj" | grep -qE '(^|[[:space:]])\.init\.data([[:space:]]|$|[[:space:]]*[-+])' ||
+	fail "patched object has no reference into .init.data; the fixture tests nothing"
+
+run_diff 255
+
+diff_log | grep -q "can't patch or reference init code/data" ||
+	fail "expected rejection, got: $(diff_log | tail -1)"
+
+pass "reference to init data rejected"