selftests/bpf: Add selftest for fill_link_info

Add selftest for the fill_link_info of uprobe, kprobe and tracepoint.
The result:

  $ tools/testing/selftests/bpf/test_progs --name=fill_link_info
  #79/1    fill_link_info/kprobe_link_info:OK
  #79/2    fill_link_info/kretprobe_link_info:OK
  #79/3    fill_link_info/kprobe_fill_invalid_user_buff:OK
  #79/4    fill_link_info/tracepoint_link_info:OK
  #79/5    fill_link_info/uprobe_link_info:OK
  #79/6    fill_link_info/uretprobe_link_info:OK
  #79/7    fill_link_info/kprobe_multi_link_info:OK
  #79/8    fill_link_info/kretprobe_multi_link_info:OK
  #79/9    fill_link_info/kprobe_multi_ubuff:OK
  #79      fill_link_info:OK
  Summary: 1/9 PASSED, 0 SKIPPED, 0 FAILED

The test case for kprobe_multi won't be run on aarch64, as it is not
supported.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>

tools/testing/selftests/bpf/DENYLIST.aarch64

@@ -12,3 +12,6 @@ kprobe_multi_test/skel_api                       # libbpf: failed to load BPF sk
 module_attach                                    # prog 'kprobe_multi': failed to auto-attach: -95
 fentry_test/fentry_many_args                     # fentry_many_args:FAIL:fentry_many_args_attach unexpected error: -524
 fexit_test/fexit_many_args                       # fexit_many_args:FAIL:fexit_many_args_attach unexpected error: -524
+fill_link_info/kprobe_multi_link_info            # bpf_program__attach_kprobe_multi_opts unexpected error: -95
+fill_link_info/kretprobe_multi_link_info         # bpf_program__attach_kprobe_multi_opts unexpected error: -95
+fill_link_info/kprobe_multi_ubuff                # bpf_program__attach_kprobe_multi_opts unexpected error: -95

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

@@ -0,0 +1,369 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
+
+#include <string.h>
+#include <linux/bpf.h>
+#include <linux/limits.h>
+#include <test_progs.h>
+#include "trace_helpers.h"
+#include "test_fill_link_info.skel.h"
+
+#define TP_CAT "sched"
+#define TP_NAME "sched_switch"
+#define KPROBE_FUNC "tcp_rcv_established"
+#define UPROBE_FILE "/proc/self/exe"
+#define KMULTI_CNT (4)
+
+/* uprobe attach point */
+static noinline void uprobe_func(void)
+{
+	asm volatile ("");
+}
+
+static int verify_perf_link_info(int fd, enum bpf_perf_event_type type, long addr,
+				 ssize_t offset, ssize_t entry_offset)
+{
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	char buf[PATH_MAX];
+	int err = 0;
+
+	memset(&info, 0, sizeof(info));
+	buf[0] = '\0';
+
+again:
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	if (!ASSERT_OK(err, "get_link_info"))
+		return -1;
+
+	switch (info.type) {
+	case BPF_LINK_TYPE_PERF_EVENT:
+		if (!ASSERT_EQ(info.perf_event.type, type, "perf_type_match"))
+			return -1;
+
+		switch (info.perf_event.type) {
+		case BPF_PERF_EVENT_KPROBE:
+		case BPF_PERF_EVENT_KRETPROBE:
+			ASSERT_EQ(info.perf_event.kprobe.offset, offset, "kprobe_offset");
+
+			/* In case kptr setting is not permitted or MAX_SYMS is reached */
+			if (addr)
+				ASSERT_EQ(info.perf_event.kprobe.addr, addr + entry_offset,
+					  "kprobe_addr");
+
+			if (!info.perf_event.kprobe.func_name) {
+				ASSERT_EQ(info.perf_event.kprobe.name_len, 0, "name_len");
+				info.perf_event.kprobe.func_name = ptr_to_u64(&buf);
+				info.perf_event.kprobe.name_len = sizeof(buf);
+				goto again;
+			}
+
+			err = strncmp(u64_to_ptr(info.perf_event.kprobe.func_name), KPROBE_FUNC,
+				      strlen(KPROBE_FUNC));
+			ASSERT_EQ(err, 0, "cmp_kprobe_func_name");
+			break;
+		case BPF_PERF_EVENT_TRACEPOINT:
+			if (!info.perf_event.tracepoint.tp_name) {
+				ASSERT_EQ(info.perf_event.tracepoint.name_len, 0, "name_len");
+				info.perf_event.tracepoint.tp_name = ptr_to_u64(&buf);
+				info.perf_event.tracepoint.name_len = sizeof(buf);
+				goto again;
+			}
+
+			err = strncmp(u64_to_ptr(info.perf_event.tracepoint.tp_name), TP_NAME,
+				      strlen(TP_NAME));
+			ASSERT_EQ(err, 0, "cmp_tp_name");
+			break;
+		case BPF_PERF_EVENT_UPROBE:
+		case BPF_PERF_EVENT_URETPROBE:
+			ASSERT_EQ(info.perf_event.uprobe.offset, offset, "uprobe_offset");
+
+			if (!info.perf_event.uprobe.file_name) {
+				ASSERT_EQ(info.perf_event.uprobe.name_len, 0, "name_len");
+				info.perf_event.uprobe.file_name = ptr_to_u64(&buf);
+				info.perf_event.uprobe.name_len = sizeof(buf);
+				goto again;
+			}
+
+			err = strncmp(u64_to_ptr(info.perf_event.uprobe.file_name), UPROBE_FILE,
+				      strlen(UPROBE_FILE));
+			ASSERT_EQ(err, 0, "cmp_file_name");
+			break;
+		default:
+			break;
+		}
+		break;
+	default:
+		switch (type) {
+		case BPF_PERF_EVENT_KPROBE:
+		case BPF_PERF_EVENT_KRETPROBE:
+		case BPF_PERF_EVENT_TRACEPOINT:
+		case BPF_PERF_EVENT_UPROBE:
+		case BPF_PERF_EVENT_URETPROBE:
+			err = -1;
+			break;
+		default:
+			break;
+		}
+		break;
+	}
+	return err;
+}
+
+static void kprobe_fill_invalid_user_buffer(int fd)
+{
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	int err;
+
+	memset(&info, 0, sizeof(info));
+
+	info.perf_event.kprobe.func_name = 0x1; /* invalid address */
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "invalid_buff_and_len");
+
+	info.perf_event.kprobe.name_len = 64;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EFAULT, "invalid_buff");
+
+	info.perf_event.kprobe.func_name = 0;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "invalid_len");
+
+	ASSERT_EQ(info.perf_event.kprobe.addr, 0, "func_addr");
+	ASSERT_EQ(info.perf_event.kprobe.offset, 0, "func_offset");
+	ASSERT_EQ(info.perf_event.type, 0, "type");
+}
+
+static void test_kprobe_fill_link_info(struct test_fill_link_info *skel,
+				       enum bpf_perf_event_type type,
+				       bool retprobe, bool invalid)
+{
+	DECLARE_LIBBPF_OPTS(bpf_kprobe_opts, opts,
+		.attach_mode = PROBE_ATTACH_MODE_LINK,
+		.retprobe = retprobe,
+	);
+	ssize_t offset = 0, entry_offset = 0;
+	int link_fd, err;
+	long addr;
+
+	skel->links.kprobe_run = bpf_program__attach_kprobe_opts(skel->progs.kprobe_run,
+								 KPROBE_FUNC, &opts);
+	if (!ASSERT_OK_PTR(skel->links.kprobe_run, "attach_kprobe"))
+		return;
+
+	link_fd = bpf_link__fd(skel->links.kprobe_run);
+	if (!ASSERT_GE(link_fd, 0, "link_fd"))
+		return;
+
+	addr = ksym_get_addr(KPROBE_FUNC);
+	if (!invalid) {
+		/* See also arch_adjust_kprobe_addr(). */
+		if (skel->kconfig->CONFIG_X86_KERNEL_IBT)
+			entry_offset = 4;
+		err = verify_perf_link_info(link_fd, type, addr, offset, offset ?: entry_offset);
+		ASSERT_OK(err, "verify_perf_link_info");
+	} else {
+		kprobe_fill_invalid_user_buffer(link_fd);
+	}
+	bpf_link__detach(skel->links.kprobe_run);
+}
+
+static void test_tp_fill_link_info(struct test_fill_link_info *skel)
+{
+	int link_fd, err;
+
+	skel->links.tp_run = bpf_program__attach_tracepoint(skel->progs.tp_run, TP_CAT, TP_NAME);
+	if (!ASSERT_OK_PTR(skel->links.tp_run, "attach_tp"))
+		return;
+
+	link_fd = bpf_link__fd(skel->links.tp_run);
+	if (!ASSERT_GE(link_fd, 0, "link_fd"))
+		return;
+
+	err = verify_perf_link_info(link_fd, BPF_PERF_EVENT_TRACEPOINT, 0, 0, 0);
+	ASSERT_OK(err, "verify_perf_link_info");
+	bpf_link__detach(skel->links.tp_run);
+}
+
+static void test_uprobe_fill_link_info(struct test_fill_link_info *skel,
+				       enum bpf_perf_event_type type, ssize_t offset,
+				       bool retprobe)
+{
+	int link_fd, err;
+
+	skel->links.uprobe_run = bpf_program__attach_uprobe(skel->progs.uprobe_run, retprobe,
+							    0, /* self pid */
+							    UPROBE_FILE, offset);
+	if (!ASSERT_OK_PTR(skel->links.uprobe_run, "attach_uprobe"))
+		return;
+
+	link_fd = bpf_link__fd(skel->links.uprobe_run);
+	if (!ASSERT_GE(link_fd, 0, "link_fd"))
+		return;
+
+	err = verify_perf_link_info(link_fd, type, 0, offset, 0);
+	ASSERT_OK(err, "verify_perf_link_info");
+	bpf_link__detach(skel->links.uprobe_run);
+}
+
+static int verify_kmulti_link_info(int fd, const __u64 *addrs, bool retprobe)
+{
+	__u64 kmulti_addrs[KMULTI_CNT];
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	int flags, i, err = 0;
+
+	memset(&info, 0, sizeof(info));
+
+again:
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	if (!ASSERT_OK(err, "get_link_info"))
+		return -1;
+
+	ASSERT_EQ(info.type, BPF_LINK_TYPE_KPROBE_MULTI, "kmulti_type");
+	switch (info.type) {
+	case BPF_LINK_TYPE_KPROBE_MULTI:
+		ASSERT_EQ(info.kprobe_multi.count, KMULTI_CNT, "func_cnt");
+		flags = info.kprobe_multi.flags & BPF_F_KPROBE_MULTI_RETURN;
+		if (!retprobe)
+			ASSERT_EQ(flags, 0, "kmulti_flags");
+		else
+			ASSERT_NEQ(flags, 0, "kretmulti_flags");
+
+		if (!info.kprobe_multi.addrs) {
+			info.kprobe_multi.addrs = ptr_to_u64(kmulti_addrs);
+			goto again;
+		}
+		for (i = 0; i < KMULTI_CNT; i++)
+			ASSERT_EQ(kmulti_addrs[i], addrs[i], "kmulti_addrs");
+		break;
+	default:
+		err = -1;
+		break;
+	}
+	return err;
+}
+
+static void verify_kmulti_user_buffer(int fd, const __u64 *addrs)
+{
+	__u64 kmulti_addrs[KMULTI_CNT];
+	struct bpf_link_info info;
+	__u32 len = sizeof(info);
+	int err, i;
+
+	memset(&info, 0, sizeof(info));
+
+	info.kprobe_multi.count = KMULTI_CNT;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "no_addr");
+
+	info.kprobe_multi.addrs = ptr_to_u64(kmulti_addrs);
+	info.kprobe_multi.count = 0;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EINVAL, "no_cnt");
+
+	for (i = 0; i < KMULTI_CNT; i++)
+		kmulti_addrs[i] = 0;
+	info.kprobe_multi.count = KMULTI_CNT - 1;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -ENOSPC, "smaller_cnt");
+	for (i = 0; i < KMULTI_CNT - 1; i++)
+		ASSERT_EQ(kmulti_addrs[i], addrs[i], "kmulti_addrs");
+	ASSERT_EQ(kmulti_addrs[i], 0, "kmulti_addrs");
+
+	for (i = 0; i < KMULTI_CNT; i++)
+		kmulti_addrs[i] = 0;
+	info.kprobe_multi.count = KMULTI_CNT + 1;
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, 0, "bigger_cnt");
+	for (i = 0; i < KMULTI_CNT; i++)
+		ASSERT_EQ(kmulti_addrs[i], addrs[i], "kmulti_addrs");
+
+	info.kprobe_multi.count = KMULTI_CNT;
+	info.kprobe_multi.addrs = 0x1; /* invalid addr */
+	err = bpf_link_get_info_by_fd(fd, &info, &len);
+	ASSERT_EQ(err, -EFAULT, "invalid_buff");
+}
+
+static int symbols_cmp_r(const void *a, const void *b)
+{
+	const char **str_a = (const char **) a;
+	const char **str_b = (const char **) b;
+
+	return strcmp(*str_a, *str_b);
+}
+
+static void test_kprobe_multi_fill_link_info(struct test_fill_link_info *skel,
+					     bool retprobe, bool buffer)
+{
+	LIBBPF_OPTS(bpf_kprobe_multi_opts, opts);
+	const char *syms[KMULTI_CNT] = {
+		"schedule_timeout_interruptible",
+		"schedule_timeout_uninterruptible",
+		"schedule_timeout_idle",
+		"schedule_timeout_killable",
+	};
+	__u64 addrs[KMULTI_CNT];
+	int link_fd, i, err = 0;
+
+	qsort(syms, KMULTI_CNT, sizeof(syms[0]), symbols_cmp_r);
+	opts.syms = syms;
+	opts.cnt = KMULTI_CNT;
+	opts.retprobe = retprobe;
+	skel->links.kmulti_run = bpf_program__attach_kprobe_multi_opts(skel->progs.kmulti_run,
+								       NULL, &opts);
+	if (!ASSERT_OK_PTR(skel->links.kmulti_run, "attach_kprobe_multi"))
+		return;
+
+	link_fd = bpf_link__fd(skel->links.kmulti_run);
+	if (!ASSERT_GE(link_fd, 0, "link_fd"))
+		return;
+
+	for (i = 0; i < KMULTI_CNT; i++)
+		addrs[i] = ksym_get_addr(syms[i]);
+
+	if (!buffer)
+		err = verify_kmulti_link_info(link_fd, addrs, retprobe);
+	else
+		verify_kmulti_user_buffer(link_fd, addrs);
+	ASSERT_OK(err, "verify_kmulti_link_info");
+	bpf_link__detach(skel->links.kmulti_run);
+}
+
+void test_fill_link_info(void)
+{
+	struct test_fill_link_info *skel;
+	ssize_t offset;
+
+	skel = test_fill_link_info__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "skel_open"))
+		goto cleanup;
+
+	/* load kallsyms to compare the addr */
+	if (!ASSERT_OK(load_kallsyms_refresh(), "load_kallsyms_refresh"))
+		return;
+	if (test__start_subtest("kprobe_link_info"))
+		test_kprobe_fill_link_info(skel, BPF_PERF_EVENT_KPROBE, false, false);
+	if (test__start_subtest("kretprobe_link_info"))
+		test_kprobe_fill_link_info(skel, BPF_PERF_EVENT_KRETPROBE, true, false);
+	if (test__start_subtest("kprobe_fill_invalid_user_buff"))
+		test_kprobe_fill_link_info(skel, BPF_PERF_EVENT_KPROBE, false, true);
+	if (test__start_subtest("tracepoint_link_info"))
+		test_tp_fill_link_info(skel);
+
+	offset = get_uprobe_offset(&uprobe_func);
+	if (test__start_subtest("uprobe_link_info"))
+		test_uprobe_fill_link_info(skel, BPF_PERF_EVENT_UPROBE, offset, false);
+	if (test__start_subtest("uretprobe_link_info"))
+		test_uprobe_fill_link_info(skel, BPF_PERF_EVENT_URETPROBE, offset, true);
+	if (test__start_subtest("kprobe_multi_link_info"))
+		test_kprobe_multi_fill_link_info(skel, false, false);
+	if (test__start_subtest("kretprobe_multi_link_info"))
+		test_kprobe_multi_fill_link_info(skel, true, false);
+	if (test__start_subtest("kprobe_multi_ubuff"))
+		test_kprobe_multi_fill_link_info(skel, true, true);
+
+cleanup:
+	test_fill_link_info__destroy(skel);
+}