selftests/bpf: Add stacktrace ips test for kprobe_multi/kretprobe_multi

Adding test that attaches kprobe/kretprobe multi and verifies the
ORC stacktrace matches expected functions.

Adding bpf_testmod_stacktrace_test function to bpf_testmod kernel
module which is called through several functions so we get reliable
call path for stacktrace.

The test is only for ORC unwinder to keep it simple.

Signed-off-by: Jiri Olsa <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>
Acked-by: Steven Rostedt (Google) <[e-mail]>

tools/testing/selftests/bpf/prog_tests/stacktrace_ips.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include "stacktrace_ips.skel.h"
+
+#ifdef __x86_64__
+static int check_stacktrace_ips(int fd, __u32 key, int cnt, ...)
+{
+	__u64 ips[PERF_MAX_STACK_DEPTH];
+	struct ksyms *ksyms = NULL;
+	int i, err = 0;
+	va_list args;
+
+	/* sorted by addr */
+	ksyms = load_kallsyms_local();
+	if (!ASSERT_OK_PTR(ksyms, "load_kallsyms_local"))
+		return -1;
+
+	/* unlikely, but... */
+	if (!ASSERT_LT(cnt, PERF_MAX_STACK_DEPTH, "check_max"))
+		return -1;
+
+	err = bpf_map_lookup_elem(fd, &key, ips);
+	if (err)
+		goto out;
+
+	/*
+	 * Compare all symbols provided via arguments with stacktrace ips,
+	 * and their related symbol addresses.t
+	 */
+	va_start(args, cnt);
+
+	for (i = 0; i < cnt; i++) {
+		unsigned long val;
+		struct ksym *ksym;
+
+		val = va_arg(args, unsigned long);
+		ksym = ksym_search_local(ksyms, ips[i]);
+		if (!ASSERT_OK_PTR(ksym, "ksym_search_local"))
+			break;
+		ASSERT_EQ(ksym->addr, val, "stack_cmp");
+	}
+
+	va_end(args);
+
+out:
+	free_kallsyms_local(ksyms);
+	return err;
+}
+
+static void test_stacktrace_ips_kprobe_multi(bool retprobe)
+{
+	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts,
+		.retprobe = retprobe
+	);
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct stacktrace_ips *skel;
+
+	skel = stacktrace_ips__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "stacktrace_ips__open_and_load"))
+		return;
+
+	if (!skel->kconfig->CONFIG_UNWINDER_ORC) {
+		test__skip();
+		goto cleanup;
+	}
+
+	skel->links.kprobe_multi_test = bpf_program__attach_kprobe_multi_opts(
+							skel->progs.kprobe_multi_test,
+							"bpf_testmod_stacktrace_test", &opts);
+	if (!ASSERT_OK_PTR(skel->links.kprobe_multi_test, "bpf_program__attach_kprobe_multi_opts"))
+		goto cleanup;
+
+	trigger_module_test_read(1);
+
+	load_kallsyms();
+
+	check_stacktrace_ips(bpf_map__fd(skel->maps.stackmap), skel->bss->stack_key, 4,
+			     ksym_get_addr("bpf_testmod_stacktrace_test_3"),
+			     ksym_get_addr("bpf_testmod_stacktrace_test_2"),
+			     ksym_get_addr("bpf_testmod_stacktrace_test_1"),
+			     ksym_get_addr("bpf_testmod_test_read"));
+
+cleanup:
+	stacktrace_ips__destroy(skel);
+}
+
+static void __test_stacktrace_ips(void)
+{
+	if (test__start_subtest("kprobe_multi"))
+		test_stacktrace_ips_kprobe_multi(false);
+	if (test__start_subtest("kretprobe_multi"))
+		test_stacktrace_ips_kprobe_multi(true);
+}
+#else
+static void __test_stacktrace_ips(void)
+{
+	test__skip();
+}
+#endif
+
+void test_stacktrace_ips(void)
+{
+	__test_stacktrace_ips();
+}

tools/testing/selftests/bpf/progs/stacktrace_ips.c

···
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+#ifndef PERF_MAX_STACK_DEPTH
+#define PERF_MAX_STACK_DEPTH         127
+#endif
+
+typedef __u64 stack_trace_t[PERF_MAX_STACK_DEPTH];
+
+struct {
+	__uint(type, BPF_MAP_TYPE_STACK_TRACE);
+	__uint(max_entries, 16384);
+	__type(key, __u32);
+	__type(value, stack_trace_t);
+} stackmap SEC(".maps");
+
+extern bool CONFIG_UNWINDER_ORC __kconfig __weak;
+
+/*
+ * This function is here to have CONFIG_UNWINDER_ORC
+ * used and added to object BTF.
+ */
+int unused(void)
+{
+	return CONFIG_UNWINDER_ORC ? 0 : 1;
+}
+
+__u32 stack_key;
+
+SEC("kprobe.multi")
+int kprobe_multi_test(struct pt_regs *ctx)
+{
+	stack_key = bpf_get_stackid(ctx, &stackmap, 0);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_kmods/bpf_testmod.c

···
 	return a + (long)b + c + d + (long)e + f + g + h + i + j + k;
 }
 
+noinline void bpf_testmod_stacktrace_test(void)
+{
+	/* used for stacktrace test as attach function */
+	asm volatile ("");
+}
+
+noinline void bpf_testmod_stacktrace_test_3(void)
+{
+	bpf_testmod_stacktrace_test();
+	asm volatile ("");
+}
+
+noinline void bpf_testmod_stacktrace_test_2(void)
+{
+	bpf_testmod_stacktrace_test_3();
+	asm volatile ("");
+}
+
+noinline void bpf_testmod_stacktrace_test_1(void)
+{
+	bpf_testmod_stacktrace_test_2();
+	asm volatile ("");
+}
+
 int bpf_testmod_fentry_ok;
 
 noinline ssize_t
···
 	    bpf_testmod_fentry_test11(16, (void *)17, 18, 19, (void *)20,
 			21, 22, 23, 24, 25, 26) != 231)
 		goto out;
+
+	bpf_testmod_stacktrace_test_1();
 
 	bpf_testmod_fentry_ok = 1;
 out: