samples/bpf/task_fd_query_user.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0

 #include <stdio.h>
 #include <stdlib.h>
 #include <signal.h>
 #include <unistd.h>
 #include <stdbool.h>
 #include <string.h>
 #include <stdint.h>
 #include <fcntl.h>
 #include <linux/bpf.h>
 #include <sys/ioctl.h>
 #include <sys/resource.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <linux/perf_event.h>

 #include <bpf/bpf.h>
 #include <bpf/libbpf.h>
 #include "bpf_util.h"
 #include "perf-sys.h"
 #include "trace_helpers.h"

 static struct bpf_program *progs[2];
 static struct bpf_link *links[2];

 #define CHECK_PERROR_RET(condition) ({			\
 	int __ret = !!(condition);			\
 	if (__ret) {					\
 		printf("FAIL: %s:\n", __func__);	\
 		perror("    ");			\
 		return -1;				\
 	}						\
 })

 #define CHECK_AND_RET(condition) ({			\
 	int __ret = !!(condition);			\
 	if (__ret)					\
 		return -1;				\
 })

 static __u64 ptr_to_u64(void *ptr)
 {
 	return (__u64) (unsigned long) ptr;
 }

 #define PMU_TYPE_FILE "/sys/bus/event_source/devices/%s/type"
 static int bpf_find_probe_type(const char *event_type)
 {
 	char buf[256];
 	int fd, ret;

 	ret = snprintf(buf, sizeof(buf), PMU_TYPE_FILE, event_type);
 	CHECK_PERROR_RET(ret < 0 || ret >= sizeof(buf));

 	fd = open(buf, O_RDONLY);
 	CHECK_PERROR_RET(fd < 0);

 	ret = read(fd, buf, sizeof(buf));
 	close(fd);
 	CHECK_PERROR_RET(ret < 0 || ret >= sizeof(buf));

 	errno = 0;
 	ret = (int)strtol(buf, NULL, 10);
 	CHECK_PERROR_RET(errno);
 	return ret;
 }

 #define PMU_RETPROBE_FILE "/sys/bus/event_source/devices/%s/format/retprobe"
 static int bpf_get_retprobe_bit(const char *event_type)
 {
 	char buf[256];
 	int fd, ret;

 	ret = snprintf(buf, sizeof(buf), PMU_RETPROBE_FILE, event_type);
 	CHECK_PERROR_RET(ret < 0 || ret >= sizeof(buf));

 	fd = open(buf, O_RDONLY);
 	CHECK_PERROR_RET(fd < 0);

 	ret = read(fd, buf, sizeof(buf));
 	close(fd);
 	CHECK_PERROR_RET(ret < 0 || ret >= sizeof(buf));
 	CHECK_PERROR_RET(strlen(buf) < strlen("config:"));

 	errno = 0;
 	ret = (int)strtol(buf + strlen("config:"), NULL, 10);
 	CHECK_PERROR_RET(errno);
 	return ret;
 }

 static int test_debug_fs_kprobe(int link_idx, const char *fn_name,
 				__u32 expected_fd_type)
 {
 	__u64 probe_offset, probe_addr;
 	__u32 len, prog_id, fd_type;
 	int err, event_fd;
 	char buf[256];

 	len = sizeof(buf);
 	event_fd = bpf_link__fd(links[link_idx]);
 	err = bpf_task_fd_query(getpid(), event_fd, 0, buf, &len,
 				&prog_id, &fd_type, &probe_offset,
 				&probe_addr);
 	if (err < 0) {
 		printf("FAIL: %s, for event_fd idx %d, fn_name %s\n",
 		       __func__, link_idx, fn_name);
 		perror("    :");
 		return -1;
 	}
 	if (strcmp(buf, fn_name) != 0 ||
 	    fd_type != expected_fd_type ||
 	    probe_offset != 0x0 || probe_addr != 0x0) {
 		printf("FAIL: bpf_trace_event_query(event_fd[%d]):\n",
 		       link_idx);
 		printf("buf: %s, fd_type: %u, probe_offset: 0x%llx,"
 		       " probe_addr: 0x%llx\n",
 		       buf, fd_type, probe_offset, probe_addr);
 		return -1;
 	}
 	return 0;
 }

 static int test_nondebug_fs_kuprobe_common(const char *event_type,
 	const char *name, __u64 offset, __u64 addr, bool is_return,
 	char *buf, __u32 *buf_len, __u32 *prog_id, __u32 *fd_type,
 	__u64 *probe_offset, __u64 *probe_addr)
 {
 	int is_return_bit = bpf_get_retprobe_bit(event_type);
 	int type = bpf_find_probe_type(event_type);
 	struct perf_event_attr attr = {};
 	struct bpf_link *link;
 	int fd, err = -1;

 	if (type < 0 || is_return_bit < 0) {
 		printf("FAIL: %s incorrect type (%d) or is_return_bit (%d)\n",
 			__func__, type, is_return_bit);
 		return err;
 	}

 	attr.sample_period = 1;
 	attr.wakeup_events = 1;
 	if (is_return)
 		attr.config |= 1 << is_return_bit;

 	if (name) {
 		attr.config1 = ptr_to_u64((void *)name);
 		attr.config2 = offset;
 	} else {
 		attr.config1 = 0;
 		attr.config2 = addr;
 	}
 	attr.size = sizeof(attr);
 	attr.type = type;

 	fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
 	link = bpf_program__attach_perf_event(progs[0], fd);
 	if (libbpf_get_error(link)) {
 		printf("ERROR: bpf_program__attach_perf_event failed\n");
 		link = NULL;
 		close(fd);
 		goto cleanup;
 	}

 	CHECK_PERROR_RET(bpf_task_fd_query(getpid(), fd, 0, buf, buf_len,
 			 prog_id, fd_type, probe_offset, probe_addr) < 0);
 	err = 0;

 cleanup:
 	bpf_link__destroy(link);
 	return err;
 }

 static int test_nondebug_fs_probe(const char *event_type, const char *name,
 				  __u64 offset, __u64 addr, bool is_return,
 				  __u32 expected_fd_type,
 				  __u32 expected_ret_fd_type,
 				  char *buf, __u32 buf_len)
 {
 	__u64 probe_offset, probe_addr;
 	__u32 prog_id, fd_type;
 	int err;

 	err = test_nondebug_fs_kuprobe_common(event_type, name,
 					      offset, addr, is_return,
 					      buf, &buf_len, &prog_id,
 					      &fd_type, &probe_offset,
 					      &probe_addr);
 	if (err < 0) {
 		printf("FAIL: %s, "
 		       "for name %s, offset 0x%llx, addr 0x%llx, is_return %d\n",
 		       __func__, name ? name : "", offset, addr, is_return);
 		perror("    :");
 		return -1;
 	}
 	if ((is_return && fd_type != expected_ret_fd_type) ||
 	    (!is_return && fd_type != expected_fd_type)) {
 		printf("FAIL: %s, incorrect fd_type %u\n",
 		       __func__, fd_type);
 		return -1;
 	}
 	if (name) {
 		if (strcmp(name, buf) != 0) {
 			printf("FAIL: %s, incorrect buf %s\n", __func__, buf);
 			return -1;
 		}
 		if (probe_offset != offset) {
 			printf("FAIL: %s, incorrect probe_offset 0x%llx\n",
 			       __func__, probe_offset);
 			return -1;
 		}
 	} else {
 		if (buf_len != 0) {
 			printf("FAIL: %s, incorrect buf %p\n",
 			       __func__, buf);
 			return -1;
 		}

 		if (probe_addr != addr) {
 			printf("FAIL: %s, incorrect probe_addr 0x%llx\n",
 			       __func__, probe_addr);
 			return -1;
 		}
 	}
 	return 0;
 }

 static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
 {
 	char buf[256], event_alias[sizeof("test_1234567890")];
 	const char *event_type = "uprobe";
 	struct perf_event_attr attr = {};
 	__u64 probe_offset, probe_addr;
 	__u32 len, prog_id, fd_type;
 	int err = -1, res, kfd, efd;
 	struct bpf_link *link;
 	ssize_t bytes;

 	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events",
 		 event_type);
 	kfd = open(buf, O_WRONLY | O_TRUNC, 0);
 	CHECK_PERROR_RET(kfd < 0);

 	res = snprintf(event_alias, sizeof(event_alias), "test_%d", getpid());
 	CHECK_PERROR_RET(res < 0 || res >= sizeof(event_alias));

 	res = snprintf(buf, sizeof(buf), "%c:%ss/%s %s:0x%lx",
 		       is_return ? 'r' : 'p', event_type, event_alias,
 		       binary_path, offset);
 	CHECK_PERROR_RET(res < 0 || res >= sizeof(buf));
 	CHECK_PERROR_RET(write(kfd, buf, strlen(buf)) < 0);

 	close(kfd);
 	kfd = -1;

 	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s/id",
 		 event_type, event_alias);
 	efd = open(buf, O_RDONLY, 0);
 	CHECK_PERROR_RET(efd < 0);

 	bytes = read(efd, buf, sizeof(buf));
 	CHECK_PERROR_RET(bytes <= 0 || bytes >= sizeof(buf));
 	close(efd);
 	buf[bytes] = '\0';

 	attr.config = strtol(buf, NULL, 0);
 	attr.type = PERF_TYPE_TRACEPOINT;
 	attr.sample_period = 1;
 	attr.wakeup_events = 1;

 	kfd = sys_perf_event_open(&attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 	link = bpf_program__attach_perf_event(progs[0], kfd);
 	if (libbpf_get_error(link)) {
 		printf("ERROR: bpf_program__attach_perf_event failed\n");
 		link = NULL;
 		close(kfd);
 		goto cleanup;
 	}

 	len = sizeof(buf);
 	err = bpf_task_fd_query(getpid(), kfd, 0, buf, &len,
 				&prog_id, &fd_type, &probe_offset,
 				&probe_addr);
 	if (err < 0) {
 		printf("FAIL: %s, binary_path %s\n", __func__, binary_path);
 		perror("    :");
 		return -1;
 	}
 	if ((is_return && fd_type != BPF_FD_TYPE_URETPROBE) ||
 	    (!is_return && fd_type != BPF_FD_TYPE_UPROBE)) {
 		printf("FAIL: %s, incorrect fd_type %u\n", __func__,
 		       fd_type);
 		return -1;
 	}
 	if (strcmp(binary_path, buf) != 0) {
 		printf("FAIL: %s, incorrect buf %s\n", __func__, buf);
 		return -1;
 	}
 	if (probe_offset != offset) {
 		printf("FAIL: %s, incorrect probe_offset 0x%llx\n", __func__,
 		       probe_offset);
 		return -1;
 	}
 	err = 0;

 cleanup:
 	bpf_link__destroy(link);
 	return err;
 }

 int main(int argc, char **argv)
 {
 	extern char __executable_start;
 	char filename[256], buf[256];
 	__u64 uprobe_file_offset;
 	struct bpf_program *prog;
 	struct bpf_object *obj;
 	int i = 0, err = -1;

 	if (load_kallsyms()) {
 		printf("failed to process /proc/kallsyms\n");
 		return err;
 	}

 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 	obj = bpf_object__open_file(filename, NULL);
 	if (libbpf_get_error(obj)) {
 		fprintf(stderr, "ERROR: opening BPF object file failed\n");
 		return err;
 	}

 	/* load BPF program */
 	if (bpf_object__load(obj)) {
 		fprintf(stderr, "ERROR: loading BPF object file failed\n");
 		goto cleanup;
 	}

 	bpf_object__for_each_program(prog, obj) {
 		progs[i] = prog;
 		links[i] = bpf_program__attach(progs[i]);
 		if (libbpf_get_error(links[i])) {
 			fprintf(stderr, "ERROR: bpf_program__attach failed\n");
 			links[i] = NULL;
 			goto cleanup;
 		}
 		i++;
 	}

 	/* test two functions in the corresponding *_kern.c file */
 	CHECK_AND_RET(test_debug_fs_kprobe(0, "blk_mq_start_request",
 					   BPF_FD_TYPE_KPROBE));
 	CHECK_AND_RET(test_debug_fs_kprobe(1, "blk_account_io_done",
 					   BPF_FD_TYPE_KRETPROBE));

 	/* test nondebug fs kprobe */
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x0, 0x0,
 					     false, BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     buf, sizeof(buf)));
 #ifdef __x86_64__
 	/* set a kprobe on "bpf_check + 0x5", which is x64 specific */
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x5, 0x0,
 					     false, BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     buf, sizeof(buf)));
 #endif
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x0, 0x0,
 					     true, BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     buf, sizeof(buf)));
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
 					     ksym_get_addr("bpf_check"), false,
 					     BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     buf, sizeof(buf)));
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
 					     ksym_get_addr("bpf_check"), false,
 					     BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     NULL, 0));
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
 					     ksym_get_addr("bpf_check"), true,
 					     BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     buf, sizeof(buf)));
 	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
 					     ksym_get_addr("bpf_check"), true,
 					     BPF_FD_TYPE_KPROBE,
 					     BPF_FD_TYPE_KRETPROBE,
 					     0, 0));

 	/* test nondebug fs uprobe */
 	/* the calculation of uprobe file offset is based on gcc 7.3.1 on x64
 	 * and the default linker script, which defines __executable_start as
 	 * the start of the .text section. The calculation could be different
 	 * on different systems with different compilers. The right way is
 	 * to parse the ELF file. We took a shortcut here.
 	 */
 	uprobe_file_offset = (unsigned long)main - (unsigned long)&__executable_start;
 	CHECK_AND_RET(test_nondebug_fs_probe("uprobe", (char *)argv[0],
 					     uprobe_file_offset, 0x0, false,
 					     BPF_FD_TYPE_UPROBE,
 					     BPF_FD_TYPE_URETPROBE,
 					     buf, sizeof(buf)));
 	CHECK_AND_RET(test_nondebug_fs_probe("uprobe", (char *)argv[0],
 					     uprobe_file_offset, 0x0, true,
 					     BPF_FD_TYPE_UPROBE,
 					     BPF_FD_TYPE_URETPROBE,
 					     buf, sizeof(buf)));

 	/* test debug fs uprobe */
 	CHECK_AND_RET(test_debug_fs_uprobe((char *)argv[0], uprobe_file_offset,
 					   false));
 	CHECK_AND_RET(test_debug_fs_uprobe((char *)argv[0], uprobe_file_offset,
 					   true));
 	err = 0;

 cleanup:
 	for (i--; i >= 0; i--)
 		bpf_link__destroy(links[i]);

 	bpf_object__close(obj);
 	return err;
 }
	// SPDX-License-Identifier: GPL-2.0

	#include <stdio.h>
	#include <stdlib.h>
	#include <signal.h>
	#include <unistd.h>
	#include <stdbool.h>
	#include <string.h>
	#include <stdint.h>
	#include <fcntl.h>
	#include <linux/bpf.h>
	#include <sys/ioctl.h>
	#include <sys/resource.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <linux/perf_event.h>

	#include <bpf/bpf.h>
	#include <bpf/libbpf.h>
	#include "bpf_util.h"
	#include "perf-sys.h"
	#include "trace_helpers.h"

	static struct bpf_program *progs[2];
	static struct bpf_link *links[2];

	#define CHECK_PERROR_RET(condition) ({ \
	int __ret = !!(condition); \
	if (__ret) { \
	printf("FAIL: %s:\n", __func__); \
	perror(" "); \
	return -1; \
	} \
	})

	#define CHECK_AND_RET(condition) ({ \
	int __ret = !!(condition); \
	if (__ret) \
	return -1; \
	})

	static __u64 ptr_to_u64(void *ptr)
	{
	return (__u64) (unsigned long) ptr;
	}

	#define PMU_TYPE_FILE "/sys/bus/event_source/devices/%s/type"
	static int bpf_find_probe_type(const char *event_type)
	{
	char buf[256];
	int fd, ret;

	ret = snprintf(buf, sizeof(buf), PMU_TYPE_FILE, event_type);
	CHECK_PERROR_RET(ret < 0 \|\| ret >= sizeof(buf));

	fd = open(buf, O_RDONLY);
	CHECK_PERROR_RET(fd < 0);

	ret = read(fd, buf, sizeof(buf));
	close(fd);
	CHECK_PERROR_RET(ret < 0 \|\| ret >= sizeof(buf));

	errno = 0;
	ret = (int)strtol(buf, NULL, 10);
	CHECK_PERROR_RET(errno);
	return ret;
	}

	#define PMU_RETPROBE_FILE "/sys/bus/event_source/devices/%s/format/retprobe"
	static int bpf_get_retprobe_bit(const char *event_type)
	{
	char buf[256];
	int fd, ret;

	ret = snprintf(buf, sizeof(buf), PMU_RETPROBE_FILE, event_type);
	CHECK_PERROR_RET(ret < 0 \|\| ret >= sizeof(buf));

	fd = open(buf, O_RDONLY);
	CHECK_PERROR_RET(fd < 0);

	ret = read(fd, buf, sizeof(buf));
	close(fd);
	CHECK_PERROR_RET(ret < 0 \|\| ret >= sizeof(buf));
	CHECK_PERROR_RET(strlen(buf) < strlen("config:"));

	errno = 0;
	ret = (int)strtol(buf + strlen("config:"), NULL, 10);
	CHECK_PERROR_RET(errno);
	return ret;
	}

	static int test_debug_fs_kprobe(int link_idx, const char *fn_name,
	__u32 expected_fd_type)
	{
	__u64 probe_offset, probe_addr;
	__u32 len, prog_id, fd_type;
	int err, event_fd;
	char buf[256];

	len = sizeof(buf);
	event_fd = bpf_link__fd(links[link_idx]);
	err = bpf_task_fd_query(getpid(), event_fd, 0, buf, &len,
	&prog_id, &fd_type, &probe_offset,
	&probe_addr);
	if (err < 0) {
	printf("FAIL: %s, for event_fd idx %d, fn_name %s\n",
	__func__, link_idx, fn_name);
	perror(" :");
	return -1;
	}
	if (strcmp(buf, fn_name) != 0 \|\|
	fd_type != expected_fd_type \|\|
	probe_offset != 0x0 \|\| probe_addr != 0x0) {
	printf("FAIL: bpf_trace_event_query(event_fd[%d]):\n",
	link_idx);
	printf("buf: %s, fd_type: %u, probe_offset: 0x%llx,"
	" probe_addr: 0x%llx\n",
	buf, fd_type, probe_offset, probe_addr);
	return -1;
	}
	return 0;
	}

	static int test_nondebug_fs_kuprobe_common(const char *event_type,
	const char *name, __u64 offset, __u64 addr, bool is_return,
	char buf, __u32 buf_len, __u32 prog_id, __u32 fd_type,
	__u64 probe_offset, __u64 probe_addr)
	{
	int is_return_bit = bpf_get_retprobe_bit(event_type);
	int type = bpf_find_probe_type(event_type);
	struct perf_event_attr attr = {};
	struct bpf_link *link;
	int fd, err = -1;

	if (type < 0 \|\| is_return_bit < 0) {
	printf("FAIL: %s incorrect type (%d) or is_return_bit (%d)\n",
	__func__, type, is_return_bit);
	return err;
	}

	attr.sample_period = 1;
	attr.wakeup_events = 1;
	if (is_return)
	attr.config \|= 1 << is_return_bit;

	if (name) {
	attr.config1 = ptr_to_u64((void *)name);
	attr.config2 = offset;
	} else {
	attr.config1 = 0;
	attr.config2 = addr;
	}
	attr.size = sizeof(attr);
	attr.type = type;

	fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
	link = bpf_program__attach_perf_event(progs[0], fd);
	if (libbpf_get_error(link)) {
	printf("ERROR: bpf_program__attach_perf_event failed\n");
	link = NULL;
	close(fd);
	goto cleanup;
	}

	CHECK_PERROR_RET(bpf_task_fd_query(getpid(), fd, 0, buf, buf_len,
	prog_id, fd_type, probe_offset, probe_addr) < 0);
	err = 0;

	cleanup:
	bpf_link__destroy(link);
	return err;
	}

	static int test_nondebug_fs_probe(const char event_type, const char name,
	__u64 offset, __u64 addr, bool is_return,
	__u32 expected_fd_type,
	__u32 expected_ret_fd_type,
	char *buf, __u32 buf_len)
	{
	__u64 probe_offset, probe_addr;
	__u32 prog_id, fd_type;
	int err;

	err = test_nondebug_fs_kuprobe_common(event_type, name,
	offset, addr, is_return,
	buf, &buf_len, &prog_id,
	&fd_type, &probe_offset,
	&probe_addr);
	if (err < 0) {
	printf("FAIL: %s, "
	"for name %s, offset 0x%llx, addr 0x%llx, is_return %d\n",
	__func__, name ? name : "", offset, addr, is_return);
	perror(" :");
	return -1;
	}
	if ((is_return && fd_type != expected_ret_fd_type) \|\|
	(!is_return && fd_type != expected_fd_type)) {
	printf("FAIL: %s, incorrect fd_type %u\n",
	__func__, fd_type);
	return -1;
	}
	if (name) {
	if (strcmp(name, buf) != 0) {
	printf("FAIL: %s, incorrect buf %s\n", __func__, buf);
	return -1;
	}
	if (probe_offset != offset) {
	printf("FAIL: %s, incorrect probe_offset 0x%llx\n",
	__func__, probe_offset);
	return -1;
	}
	} else {
	if (buf_len != 0) {
	printf("FAIL: %s, incorrect buf %p\n",
	__func__, buf);
	return -1;
	}

	if (probe_addr != addr) {
	printf("FAIL: %s, incorrect probe_addr 0x%llx\n",
	__func__, probe_addr);
	return -1;
	}
	}
	return 0;
	}

	static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
	{
	char buf[256], event_alias[sizeof("test_1234567890")];
	const char *event_type = "uprobe";
	struct perf_event_attr attr = {};
	__u64 probe_offset, probe_addr;
	__u32 len, prog_id, fd_type;
	int err = -1, res, kfd, efd;
	struct bpf_link *link;
	ssize_t bytes;

	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/%s_events",
	event_type);
	kfd = open(buf, O_WRONLY \| O_TRUNC, 0);
	CHECK_PERROR_RET(kfd < 0);

	res = snprintf(event_alias, sizeof(event_alias), "test_%d", getpid());
	CHECK_PERROR_RET(res < 0 \|\| res >= sizeof(event_alias));

	res = snprintf(buf, sizeof(buf), "%c:%ss/%s %s:0x%lx",
	is_return ? 'r' : 'p', event_type, event_alias,
	binary_path, offset);
	CHECK_PERROR_RET(res < 0 \|\| res >= sizeof(buf));
	CHECK_PERROR_RET(write(kfd, buf, strlen(buf)) < 0);

	close(kfd);
	kfd = -1;

	snprintf(buf, sizeof(buf), "/sys/kernel/debug/tracing/events/%ss/%s/id",
	event_type, event_alias);
	efd = open(buf, O_RDONLY, 0);
	CHECK_PERROR_RET(efd < 0);

	bytes = read(efd, buf, sizeof(buf));
	CHECK_PERROR_RET(bytes <= 0 \|\| bytes >= sizeof(buf));
	close(efd);
	buf[bytes] = '\0';

	attr.config = strtol(buf, NULL, 0);
	attr.type = PERF_TYPE_TRACEPOINT;
	attr.sample_period = 1;
	attr.wakeup_events = 1;

	kfd = sys_perf_event_open(&attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
	link = bpf_program__attach_perf_event(progs[0], kfd);
	if (libbpf_get_error(link)) {
	printf("ERROR: bpf_program__attach_perf_event failed\n");
	link = NULL;
	close(kfd);
	goto cleanup;
	}

	len = sizeof(buf);
	err = bpf_task_fd_query(getpid(), kfd, 0, buf, &len,
	&prog_id, &fd_type, &probe_offset,
	&probe_addr);
	if (err < 0) {
	printf("FAIL: %s, binary_path %s\n", __func__, binary_path);
	perror(" :");
	return -1;
	}
	if ((is_return && fd_type != BPF_FD_TYPE_URETPROBE) \|\|
	(!is_return && fd_type != BPF_FD_TYPE_UPROBE)) {
	printf("FAIL: %s, incorrect fd_type %u\n", __func__,
	fd_type);
	return -1;
	}
	if (strcmp(binary_path, buf) != 0) {
	printf("FAIL: %s, incorrect buf %s\n", __func__, buf);
	return -1;
	}
	if (probe_offset != offset) {
	printf("FAIL: %s, incorrect probe_offset 0x%llx\n", __func__,
	probe_offset);
	return -1;
	}
	err = 0;

	cleanup:
	bpf_link__destroy(link);
	return err;
	}

	int main(int argc, char **argv)
	{
	extern char __executable_start;
	char filename[256], buf[256];
	__u64 uprobe_file_offset;
	struct bpf_program *prog;
	struct bpf_object *obj;
	int i = 0, err = -1;

	if (load_kallsyms()) {
	printf("failed to process /proc/kallsyms\n");
	return err;
	}

	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
	obj = bpf_object__open_file(filename, NULL);
	if (libbpf_get_error(obj)) {
	fprintf(stderr, "ERROR: opening BPF object file failed\n");
	return err;
	}

	/* load BPF program */
	if (bpf_object__load(obj)) {
	fprintf(stderr, "ERROR: loading BPF object file failed\n");
	goto cleanup;
	}

	bpf_object__for_each_program(prog, obj) {
	progs[i] = prog;
	links[i] = bpf_program__attach(progs[i]);
	if (libbpf_get_error(links[i])) {
	fprintf(stderr, "ERROR: bpf_program__attach failed\n");
	links[i] = NULL;
	goto cleanup;
	}
	i++;
	}

	/* test two functions in the corresponding _kern.c file /
	CHECK_AND_RET(test_debug_fs_kprobe(0, "blk_mq_start_request",
	BPF_FD_TYPE_KPROBE));
	CHECK_AND_RET(test_debug_fs_kprobe(1, "blk_account_io_done",
	BPF_FD_TYPE_KRETPROBE));

	/* test nondebug fs kprobe */
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x0, 0x0,
	false, BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	buf, sizeof(buf)));
	#ifdef __x86_64__
	/* set a kprobe on "bpf_check + 0x5", which is x64 specific */
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x5, 0x0,
	false, BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	buf, sizeof(buf)));
	#endif
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", "bpf_check", 0x0, 0x0,
	true, BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	buf, sizeof(buf)));
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
	ksym_get_addr("bpf_check"), false,
	BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	buf, sizeof(buf)));
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
	ksym_get_addr("bpf_check"), false,
	BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	NULL, 0));
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
	ksym_get_addr("bpf_check"), true,
	BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	buf, sizeof(buf)));
	CHECK_AND_RET(test_nondebug_fs_probe("kprobe", NULL, 0x0,
	ksym_get_addr("bpf_check"), true,
	BPF_FD_TYPE_KPROBE,
	BPF_FD_TYPE_KRETPROBE,
	0, 0));

	/* test nondebug fs uprobe */
	/* the calculation of uprobe file offset is based on gcc 7.3.1 on x64
	* and the default linker script, which defines __executable_start as
	* the start of the .text section. The calculation could be different
	* on different systems with different compilers. The right way is
	* to parse the ELF file. We took a shortcut here.
	*/
	uprobe_file_offset = (unsigned long)main - (unsigned long)&__executable_start;
	CHECK_AND_RET(test_nondebug_fs_probe("uprobe", (char *)argv[0],
	uprobe_file_offset, 0x0, false,
	BPF_FD_TYPE_UPROBE,
	BPF_FD_TYPE_URETPROBE,
	buf, sizeof(buf)));
	CHECK_AND_RET(test_nondebug_fs_probe("uprobe", (char *)argv[0],
	uprobe_file_offset, 0x0, true,
	BPF_FD_TYPE_UPROBE,
	BPF_FD_TYPE_URETPROBE,
	buf, sizeof(buf)));

	/* test debug fs uprobe */
	CHECK_AND_RET(test_debug_fs_uprobe((char *)argv[0], uprobe_file_offset,
	false));
	CHECK_AND_RET(test_debug_fs_uprobe((char *)argv[0], uprobe_file_offset,
	true));
	err = 0;

	cleanup:
	for (i--; i >= 0; i--)
	bpf_link__destroy(links[i]);

	bpf_object__close(obj);
	return err;
	}