[PATCH v2 3/3] objtool/klp: Add test for changed functions without an ftrace call site

[Puranjay Mohan <puranjay@kernel.org>]

Test that klp diff rejects a changed function without an ftrace call
site, both a notrace one and an inline one emitted out of line, and
reports each of them.  Also test that a fully inlined function and an
ordinary function can still be patched.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
---
 .../tests/x86/fixtures/notrace_target.c       | 71 ++++++++++++++++++
 .../objtool/tests/x86/test-notrace-target.sh  | 74 +++++++++++++++++++
 2 files changed, 145 insertions(+)
 create mode 100644 tools/objtool/tests/x86/fixtures/notrace_target.c
 create mode 100755 tools/objtool/tests/x86/test-notrace-target.sh

diff --git a/tools/objtool/tests/x86/fixtures/notrace_target.c b/tools/objtool/tests/x86/fixtures/notrace_target.c
new file mode 100644
index 0000000000000..64da58c872b8a
--- /dev/null
+++ b/tools/objtool/tests/x86/fixtures/notrace_target.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+/* PATCH_<name> changes <name> in the patched build. */
+#define notrace __attribute__((__no_instrument_function__))
+
+static const char __modinfo[]
+	__attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
+
+#ifndef PATCHED
+#undef PATCH_OUTLINED
+#undef PATCH_NOTRACE
+#undef PATCH_INLINED
+#undef PATCH_TRACED
+#endif
+
+#ifdef PATCH_OUTLINED
+#define OUTLINED_K 2
+#else
+#define OUTLINED_K 1
+#endif
+
+#ifdef PATCH_NOTRACE
+#define NOTRACE_K 2
+#else
+#define NOTRACE_K 1
+#endif
+
+#ifdef PATCH_INLINED
+#define INLINED_K 2
+#else
+#define INLINED_K 1
+#endif
+
+#ifdef PATCH_TRACED
+#define TRACED_K 2
+#else
+#define TRACED_K 1
+#endif
+
+int sink;
+
+/* Address taken, so emitted out of line. */
+static inline notrace int outlined(int x)
+{
+	int i;
+
+	for (i = 0; i < x; i++)
+		sink += i * OUTLINED_K;
+	return sink;
+}
+
+int (*outlined_ptr)(int) = outlined;
+
+notrace int notrace_fn(int x)
+{
+	return x * 3 + NOTRACE_K;
+}
+
+static inline int inlined(int x)
+{
+	return x + INLINED_K;
+}
+
+int inlined_user(int x)
+{
+	return inlined(x) * 5;
+}
+
+int traced(int x)
+{
+	return x * 7 + TRACED_K;
+}
diff --git a/tools/objtool/tests/x86/test-notrace-target.sh b/tools/objtool/tests/x86/test-notrace-target.sh
new file mode 100755
index 0000000000000..09414ae65fc2c
--- /dev/null
+++ b/tools/objtool/tests/x86/test-notrace-target.sh
@@ -0,0 +1,74 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# A changed function without an ftrace call site can't be livepatched:
+# klp_enable_patch() fails with "failed to find location for function".
+# klp diff must reject it instead.
+
+. "$(dirname "$0")/../lib.sh"
+
+# mcount_entry <function>: orig.o has an __mcount_loc entry for it.
+mcount_entry()
+{
+	in_relocs "$orig_obj" | awk '/rela__mcount_loc/,/^$/' |
+		awk -v f="$1" '$5 == f || $5 == ".text." f' | grep -q .
+}
+
+# check <expected exit status> <-DPATCH_... flags>
+check()
+{
+	local expect="$1"; shift
+
+	setup
+	build_pair notrace_target.c "$@"
+
+	assert_input_symbol outlined
+	assert_input_symbol notrace_fn
+	has_input_symbol "$orig_obj" inlined &&
+		fail "inlined() was emitted out of line; the fixture tests nothing"
+	mcount_entry traced ||
+		fail "no __mcount_loc entry for traced(); the fixture tests nothing"
+	mcount_entry inlined_user ||
+		fail "no __mcount_loc entry for inlined_user(); the fixture tests nothing"
+	mcount_entry outlined &&
+		fail "outlined() has a __mcount_loc entry; it should be notrace"
+	mcount_entry notrace_fn &&
+		fail "notrace_fn() has a __mcount_loc entry; it should be notrace"
+
+	run_diff "$expect"
+}
+
+rejected()
+{
+	local n
+
+	n="$(diff_log | grep -c "error: objtool: $1: no ftrace call site, can't patch")"
+	[ "$n" = 1 ] ||
+		fail "expected '$1' rejected once, found $n: $(diff_log | tail -2)"
+}
+
+check 255 -DPATCH_OUTLINED
+rejected outlined
+cleanup
+
+check 255 -DPATCH_NOTRACE
+rejected notrace_fn
+cleanup
+
+check 255 -DPATCH_OUTLINED -DPATCH_NOTRACE
+rejected outlined
+rejected notrace_fn
+cleanup
+
+# Fully inlined: the traceable caller gets patched.
+check 0 -DPATCH_INLINED
+assert_patched inlined_user
+assert_not_patched traced
+cleanup
+
+check 0 -DPATCH_TRACED
+assert_patched traced
+assert_not_patched inlined_user
+cleanup
+
+pass "changed function without an ftrace call site rejected"
-- 
2.53.0-Meta