selftests/bpf: Add callchain_stackid

This tests new helper function bpf_get_stackid_pe and bpf_get_stack_pe.
These two helpers have different implementation for perf_event with PEB
entries.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200723180648.1429892-5-songliubraving@fb.com

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sched.h>
+#include <test_progs.h>
+#include "perf_event_stackmap.skel.h"
+
+#ifndef noinline
+#define noinline __attribute__((noinline))
+#endif
+
+noinline int func_1(void)
+{
+	static int val = 1;
+
+	val += 1;
+
+	usleep(100);
+	return val;
+}
+
+noinline int func_2(void)
+{
+	return func_1();
+}
+
+noinline int func_3(void)
+{
+	return func_2();
+}
+
+noinline int func_4(void)
+{
+	return func_3();
+}
+
+noinline int func_5(void)
+{
+	return func_4();
+}
+
+noinline int func_6(void)
+{
+	int i, val = 1;
+
+	for (i = 0; i < 100; i++)
+		val += func_5();
+
+	return val;
+}
+
+void test_perf_event_stackmap(void)
+{
+	struct perf_event_attr attr = {
+		/* .type = PERF_TYPE_SOFTWARE, */
+		.type = PERF_TYPE_HARDWARE,
+		.config = PERF_COUNT_HW_CPU_CYCLES,
+		.precise_ip = 2,
+		.sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_BRANCH_STACK |
+			PERF_SAMPLE_CALLCHAIN,
+		.branch_sample_type = PERF_SAMPLE_BRANCH_USER |
+			PERF_SAMPLE_BRANCH_NO_FLAGS |
+			PERF_SAMPLE_BRANCH_NO_CYCLES |
+			PERF_SAMPLE_BRANCH_CALL_STACK,
+		.sample_period = 5000,
+		.size = sizeof(struct perf_event_attr),
+	};
+	struct perf_event_stackmap *skel;
+	__u32 duration = 0;
+	cpu_set_t cpu_set;
+	int pmu_fd, err;
+
+	skel = perf_event_stackmap__open();
+
+	if (CHECK(!skel, "skel_open", "skeleton open failed\n"))
+		return;
+
+	err = perf_event_stackmap__load(skel);
+	if (CHECK(err, "skel_load", "skeleton load failed: %d\n", err))
+		goto cleanup;
+
+	CPU_ZERO(&cpu_set);
+	CPU_SET(0, &cpu_set);
+	err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set);
+	if (CHECK(err, "set_affinity", "err %d, errno %d\n", err, errno))
+		goto cleanup;
+
+	pmu_fd = syscall(__NR_perf_event_open, &attr, -1 /* pid */,
+			 0 /* cpu 0 */, -1 /* group id */,
+			 0 /* flags */);
+	if (pmu_fd < 0) {
+		printf("%s:SKIP:cpu doesn't support the event\n", __func__);
+		test__skip();
+		goto cleanup;
+	}
+
+	skel->links.oncpu = bpf_program__attach_perf_event(skel->progs.oncpu,
+							   pmu_fd);
+	if (CHECK(IS_ERR(skel->links.oncpu), "attach_perf_event",
+		  "err %ld\n", PTR_ERR(skel->links.oncpu))) {
+		close(pmu_fd);
+		goto cleanup;
+	}
+
+	/* create kernel and user stack traces for testing */
+	func_6();
+
+	CHECK(skel->data->stackid_kernel != 2, "get_stackid_kernel", "failed\n");
+	CHECK(skel->data->stackid_user != 2, "get_stackid_user", "failed\n");
+	CHECK(skel->data->stack_kernel != 2, "get_stack_kernel", "failed\n");
+	CHECK(skel->data->stack_user != 2, "get_stack_user", "failed\n");
+
+cleanup:
+	perf_event_stackmap__destroy(skel);
+}

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

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.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);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(stack_trace_t));
+} stackmap SEC(".maps");
+
+struct {
+	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__type(value, stack_trace_t);
+} stackdata_map SEC(".maps");
+
+long stackid_kernel = 1;
+long stackid_user = 1;
+long stack_kernel = 1;
+long stack_user = 1;
+
+SEC("perf_event")
+int oncpu(void *ctx)
+{
+	stack_trace_t *trace;
+	__u32 key = 0;
+	long val;
+
+	val = bpf_get_stackid(ctx, &stackmap, 0);
+	if (val > 0)
+		stackid_kernel = 2;
+	val = bpf_get_stackid(ctx, &stackmap, BPF_F_USER_STACK);
+	if (val > 0)
+		stackid_user = 2;
+
+	trace = bpf_map_lookup_elem(&stackdata_map, &key);
+	if (!trace)
+		return 0;
+
+	val = bpf_get_stack(ctx, trace, sizeof(stack_trace_t), 0);
+	if (val > 0)
+		stack_kernel = 2;
+
+	val = bpf_get_stack(ctx, trace, sizeof(stack_trace_t), BPF_F_USER_STACK);
+	if (val > 0)
+		stack_user = 2;
+
+	return 0;
+}
+
+char LICENSE[] SEC("license") = "GPL";