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samples, bpf: Refactor perf_event user program with libbpf bpf_link

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The bpf_program__attach of libbpf(using bpf_link) is much more intuitive
than the previous method using ioctl.

bpf_program__attach_perf_event manages the enable of perf_event and
attach of BPF programs to it, so there's no neeed to do this
directly with ioctl.

In addition, bpf_link provides consistency in the use of API because it
allows disable (detach, destroy) for multiple events to be treated as
one bpf_link__destroy. Also, bpf_link__destroy manages the close() of
perf_event fd.

This commit refactors samples that attach the bpf program to perf_event
by using libbbpf instead of ioctl. Also the bpf_load in the samples were
removed and migrated to use libbbpf API.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200321100424.1593964-3-danieltimlee@gmail.com
This commit is contained in:
Daniel T. Lee 2020-03-21 19:04:24 +09:00 • committed by Daniel Borkmann
parent 24a6034acc
commit aa5e2af660
3 changed files with 160 additions and 83 deletions
Download patch file Download diff file Expand all files Collapse all files

141
samples/bpf/trace_event_user.c
View file

@ -6,22 +6,25 @@
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <linux/bpf.h>
#include <signal.h>
#include <assert.h>
#include <errno.h>
#include <sys/resource.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "bpf_load.h"
#include "perf-sys.h"
#include "trace_helpers.h"
#define __must_check
#include <linux/err.h>
#define SAMPLE_FREQ 50
static int pid;
/* counts, stackmap */
static int map_fd[2];
struct bpf_program *prog;
static bool sys_read_seen, sys_write_seen;
static void print_ksym(__u64 addr)
@ -91,10 +94,10 @@ static void print_stack(struct key_t *key, __u64 count)
}
}
static void int_exit(int sig)
static void err_exit(int err)
{
kill(0, SIGKILL);
exit(0);
kill(pid, SIGKILL);
exit(err);
}
static void print_stacks(void)
@ -102,7 +105,7 @@ static void print_stacks(void)
struct key_t key = {}, next_key;
__u64 value;
__u32 stackid = 0, next_id;
int fd = map_fd[0], stack_map = map_fd[1];
int error = 1, fd = map_fd[0], stack_map = map_fd[1];
sys_read_seen = sys_write_seen = false;
while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
@ -114,7 +117,7 @@ static void print_stacks(void)
printf("\n");
if (!sys_read_seen || !sys_write_seen) {
printf("BUG kernel stack doesn't contain sys_read() and sys_write()\n");
int_exit(0);
err_exit(error);
}
/* clear stack map */
@ -136,43 +139,52 @@ static inline int generate_load(void)
static void test_perf_event_all_cpu(struct perf_event_attr *attr)
{
int nr_cpus = sysconf(_SC_NPROCESSORS_CONF);
int *pmu_fd = malloc(nr_cpus * sizeof(int));
int i, error = 0;
int nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
struct bpf_link **links = calloc(nr_cpus, sizeof(struct bpf_link *));
int i, pmu_fd, error = 1;
if (!links) {
printf("malloc of links failed\n");
goto err;
}
/* system wide perf event, no need to inherit */
attr->inherit = 0;
/* open perf_event on all cpus */
for (i = 0; i < nr_cpus; i++) {
pmu_fd[i] = sys_perf_event_open(attr, -1, i, -1, 0);
if (pmu_fd[i] < 0) {
pmu_fd = sys_perf_event_open(attr, -1, i, -1, 0);
if (pmu_fd < 0) {
printf("sys_perf_event_open failed\n");
error = 1;
goto all_cpu_err;
}
assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
assert(ioctl(pmu_fd[i], PERF_EVENT_IOC_ENABLE) == 0);
links[i] = bpf_program__attach_perf_event(prog, pmu_fd);
if (IS_ERR(links[i])) {
printf("bpf_program__attach_perf_event failed\n");
links[i] = NULL;
close(pmu_fd);
goto all_cpu_err;
}
}
if (generate_load() < 0) {
error = 1;
if (generate_load() < 0)
goto all_cpu_err;
}
print_stacks();
error = 0;
all_cpu_err:
for (i--; i >= 0; i--) {
ioctl(pmu_fd[i], PERF_EVENT_IOC_DISABLE);
close(pmu_fd[i]);
}
free(pmu_fd);
for (i--; i >= 0; i--)
bpf_link__destroy(links[i]);
err:
free(links);
if (error)
int_exit(0);
err_exit(error);
}
static void test_perf_event_task(struct perf_event_attr *attr)
{
int pmu_fd, error = 0;
struct bpf_link *link = NULL;
int pmu_fd, error = 1;
/* per task perf event, enable inherit so the "dd ..." command can be traced properly.
* Enabling inherit will cause bpf_perf_prog_read_time helper failure.
@ -183,21 +195,25 @@ static void test_perf_event_task(struct perf_event_attr *attr)
pmu_fd = sys_perf_event_open(attr, 0, -1, -1, 0);
if (pmu_fd < 0) {
printf("sys_perf_event_open failed\n");
int_exit(0);
}
assert(ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) == 0);
assert(ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE) == 0);
if (generate_load() < 0) {
error = 1;
goto err;
}
link = bpf_program__attach_perf_event(prog, pmu_fd);
if (IS_ERR(link)) {
printf("bpf_program__attach_perf_event failed\n");
link = NULL;
close(pmu_fd);
goto err;
}
if (generate_load() < 0)
goto err;
print_stacks();
error = 0;
err:
ioctl(pmu_fd, PERF_EVENT_IOC_DISABLE);
close(pmu_fd);
bpf_link__destroy(link);
if (error)
int_exit(0);
err_exit(error);
}
static void test_bpf_perf_event(void)
@ -282,29 +298,60 @@ static void test_bpf_perf_event(void)
int main(int argc, char **argv)
{
struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
struct bpf_object *obj = NULL;
char filename[256];
int error = 1;
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
setrlimit(RLIMIT_MEMLOCK, &r);
signal(SIGINT, int_exit);
signal(SIGTERM, int_exit);
signal(SIGINT, err_exit);
signal(SIGTERM, err_exit);
if (load_kallsyms()) {
printf("failed to process /proc/kallsyms\n");
return 1;
goto cleanup;
}
if (load_bpf_file(filename)) {
printf("%s", bpf_log_buf);
return 2;
obj = bpf_object__open_file(filename, NULL);
if (IS_ERR(obj)) {
printf("opening BPF object file failed\n");
obj = NULL;
goto cleanup;
}
if (fork() == 0) {
prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
if (!prog) {
printf("finding a prog in obj file failed\n");
goto cleanup;
}
/* load BPF program */
if (bpf_object__load(obj)) {
printf("loading BPF object file failed\n");
goto cleanup;
}
map_fd[0] = bpf_object__find_map_fd_by_name(obj, "counts");
map_fd[1] = bpf_object__find_map_fd_by_name(obj, "stackmap");
if (map_fd[0] < 0 || map_fd[1] < 0) {
printf("finding a counts/stackmap map in obj file failed\n");
goto cleanup;
}
pid = fork();
if (pid == 0) {
read_trace_pipe();
return 0;
} else if (pid == -1) {
printf("couldn't spawn process\n");
goto cleanup;
}
test_bpf_perf_event();
int_exit(0);
return 0;
error = 0;
cleanup:
bpf_object__close(obj);
err_exit(error);
}