2 files changed, 120 insertions, 0 deletions
diff --git a/tools/objtool/tests/generic/fixtures/jump_label.c b/tools/objtool/tests/generic/fixtures/jump_label.c
new file mode 100644
index 000000000000..ecd3c06912af
--- /dev/null
+++ b/tools/objtool/tests/generic/fixtures/jump_label.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Static branch in a patched function.  The jump table entry is written out by
+ * hand, mirroring JUMP_TABLE_ENTRY(), so the fixture builds without kernel
+ * headers.  The key is an STT_OBJECT; anything else is ignored by
+ * validate_special_section_klp_reloc().
+ *
+ * MODNAME selects whether the key is taken to belong to vmlinux or a module.
+ *
+ * NEW_KEY puts the whole static branch behind PATCHED, so the patch introduces
+ * one where the original had none -- a different question from patching code
+ * that already has a key, because the __jump_table entry itself is new.
+ *
+ * KEY_NAME renames the key.  Two names are special to
+ * validate_special_section_klp_reloc(): a __tracepoint_* key and the
+ * __UNIQUE_ID_ddebug_* one pr_debug() generates are both unsupported in a
+ * module, but are disabled with a warning rather than rejected, because the
+ * kernel is full of them and refusing outright would make ordinary functions
+ * unpatchable.
+ *
+ * STATIC_KEY makes the key file-local.  That changes the shape of the
+ * relocation rather than the meaning of the code: a reference to a static lands
+ * on the section symbol plus an addend, so the key has to be resolved from the
+ * section before it can be recognised as a key at all.
+ */
+
+#ifndef MODNAME
+#define MODNAME "vmlinux"
+#endif
+
+#ifndef KEY_NAME
+#define KEY_NAME klp_test_key
+#endif
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=" MODNAME;
+
+#ifdef STATIC_KEY
+static long KEY_NAME;
+#else
+long KEY_NAME;
+#endif
+
+int target(int x)
+{
+	int r = x;
+
+#if defined(NEW_KEY) && !defined(PATCHED)
+	/* The original has no static branch at all. */
+	return r + 1;
+#else
+	asm goto(
+		"1:	nop\n\t"
+		".pushsection	__jump_table, \"aw\"\n\t"
+		".balign	8\n\t"
+		"912:\n\t"
+		".pushsection	.discard.annotate_data, \"M\", @progbits, 8\n\t"
+		".long		912b - ., 1\n\t"
+		".popsection\n\t"
+		".long		1b - ., %l[l_yes] - .\n\t"
+		".quad		%c0 - .\n\t"
+		".popsection\n\t"
+		: : "i" (&KEY_NAME) : : l_yes);
+
+	r += 1;
+	goto out;
+l_yes:
+	r += 2;
+out:
+#endif
+#ifdef PATCHED
+	return r + 100;
+#else
+	return r;
+#endif
+}
diff --git a/tools/objtool/tests/generic/test-jump-label-key.sh b/tools/objtool/tests/generic/test-jump-label-key.sh
new file mode 100755
index 000000000000..142f94bd38ec
--- /dev/null
+++ b/tools/objtool/tests/generic/test-jump-label-key.sh
@@ -0,0 +1,44 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# A cloned __jump_table entry must keep a relocation in its key slot, whether
+# the key needs a klp relocation or not.
+
+. "$(dirname "$0")/../lib.sh"
+
+key=klp_test_key
+
+setup
+build_pair jump_label.c
+
+has_input_section orig.o __jump_table ||
+	probe_skip "fixture produced no __jump_table on this arch"
+
+key_slot_relocs()
+{
+	out_relocs | awk '/rela__jump_table/,/^$/' | grep -c "^0*8[[:space:]]"
+}
+
+# Unexported: klp relocation, key slot holds a tombstone.
+export_syms
+run_diff
+
+[ "$(key_slot_relocs)" = 1 ] ||
+	fail "unexported key: key slot has no relocation"
+out_relocs | awk '/rela__jump_table/,/^$/' | grep -q "\.klp\.tombstone\.$key" ||
+	fail "unexported key: expected a .klp.tombstone.$key relocation"
+out_symbols | grep -q "\.klp\.sym\..*\.$key," ||
+	fail "unexported key: no .klp.sym reference for the real relocation"
+
+# Exported: ordinary relocation, no klp machinery.
+export_syms "$key"
+run_diff
+
+[ "$(key_slot_relocs)" = 1 ] ||
+	fail "exported key: key slot has no relocation"
+out_relocs | awk '/rela__jump_table/,/^$/' | grep -q "[[:space:]]$key[[:space:]]*+" ||
+	fail "exported key: expected a direct relocation to $key"
+out_symbols | grep -q '\.klp\.tombstone\.' &&
+	fail "exported key: tombstone emitted for an exported symbol"
+
+pass "key slot populated for exported and unexported vmlinux keys"