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samples: bpf: Refactor task_fd_query program with libbpf

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This commit refactors the existing kprobe program with libbpf bpf
loader. To attach bpf program, this uses generic bpf_program__attach()
approach rather than using bpf_load's load_bpf_file().

To attach bpf to perf_event, instead of using previous ioctl method,
this commit uses bpf_program__attach_perf_event since it manages the
enable of perf_event and attach of BPF programs to it, which is much
more intuitive way to achieve.

Also, explicit close(fd) has been removed since event will be closed
inside bpf_link__destroy() automatically.

Furthermore, to prevent conflict of same named uprobe events, O_TRUNC
flag has been used to clear 'uprobe_events' interface.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201124090310.24374-4-danieltimlee@gmail.com
This commit is contained in:
Daniel T. Lee 2020-11-24 09:03:06 +00:00 committed by Andrii Nakryiko
parent d89af13c92
commit 4fe6641526
2 changed files with 75 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
samples/bpf/Makefile
View File

@ -107,7 +107,7 @@ xdp_adjust_tail-objs := xdp_adjust_tail_user.o
xdpsock-objs := xdpsock_user.o
xsk_fwd-objs := xsk_fwd.o
xdp_fwd-objs := xdp_fwd_user.o
task_fd_query-objs := bpf_load.o task_fd_query_user.o $(TRACE_HELPERS)
task_fd_query-objs := task_fd_query_user.o $(TRACE_HELPERS)
xdp_sample_pkts-objs := xdp_sample_pkts_user.o $(TRACE_HELPERS)
ibumad-objs := bpf_load.o ibumad_user.o $(TRACE_HELPERS)
hbm-objs := hbm.o $(CGROUP_HELPERS)

101
samples/bpf/task_fd_query_user.c
View File

@ -15,12 +15,15 @@
#include <sys/stat.h>
#include <linux/perf_event.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "bpf_load.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) { \
@ -86,21 +89,22 @@ static int bpf_get_retprobe_bit(const char *event_type)
return ret;
}
static int test_debug_fs_kprobe(int prog_fd_idx, const char *fn_name,
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];
int err;
len = sizeof(buf);
err = bpf_task_fd_query(getpid(), event_fd[prog_fd_idx], 0, buf, &len,
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__, prog_fd_idx, fn_name);
__func__, link_idx, fn_name);
perror(" :");
return -1;
}
@ -108,7 +112,7 @@ static int test_debug_fs_kprobe(int prog_fd_idx, const char *fn_name,
fd_type != expected_fd_type ||
probe_offset != 0x0 || probe_addr != 0x0) {
printf("FAIL: bpf_trace_event_query(event_fd[%d]):\n",
prog_fd_idx);
link_idx);
printf("buf: %s, fd_type: %u, probe_offset: 0x%llx,"
" probe_addr: 0x%llx\n",
buf, fd_type, probe_offset, probe_addr);
@ -125,12 +129,13 @@ static int test_nondebug_fs_kuprobe_common(const char *event_type,
int is_return_bit = bpf_get_retprobe_bit(event_type);
int type = bpf_find_probe_type(event_type);
struct perf_event_attr attr = {};
int fd;
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 -1;
return err;
}
attr.sample_period = 1;
@ -149,14 +154,21 @@ static int test_nondebug_fs_kuprobe_common(const char *event_type,
attr.type = type;
fd = sys_perf_event_open(&attr, -1, 0, -1, 0);
CHECK_PERROR_RET(fd < 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(ioctl(fd, PERF_EVENT_IOC_ENABLE, 0) < 0);
CHECK_PERROR_RET(ioctl(fd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) < 0);
CHECK_PERROR_RET(bpf_task_fd_query(getpid(), fd, 0, buf, buf_len,
prog_id, fd_type, probe_offset, probe_addr) < 0);
err = 0;
return 0;
cleanup:
bpf_link__destroy(link);
return err;
}
static int test_nondebug_fs_probe(const char *event_type, const char *name,
@ -215,17 +227,18 @@ static int test_nondebug_fs_probe(const char *event_type, const char *name,
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 = {};
char buf[256], event_alias[sizeof("test_1234567890")];
__u64 probe_offset, probe_addr;
__u32 len, prog_id, fd_type;
int err, res, kfd, efd;
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_APPEND, 0);
kfd = open(buf, O_WRONLY | O_TRUNC, 0);
CHECK_PERROR_RET(kfd < 0);
res = snprintf(event_alias, sizeof(event_alias), "test_%d", getpid());
@ -254,10 +267,15 @@ static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
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);
CHECK_PERROR_RET(kfd < 0);
CHECK_PERROR_RET(ioctl(kfd, PERF_EVENT_IOC_SET_BPF, prog_fd[0]) < 0);
CHECK_PERROR_RET(ioctl(kfd, PERF_EVENT_IOC_ENABLE, 0) < 0);
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,
@ -283,9 +301,11 @@ static int test_debug_fs_uprobe(char *binary_path, long offset, bool is_return)
probe_offset);
return -1;
}
err = 0;
close(kfd);
return 0;
cleanup:
bpf_link__destroy(link);
return err;
}
int main(int argc, char **argv)
@ -294,21 +314,42 @@ 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;
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
if (setrlimit(RLIMIT_MEMLOCK, &r)) {
perror("setrlimit(RLIMIT_MEMLOCK)");
return 1;
return err;
}
if (load_kallsyms()) {
printf("failed to process /proc/kallsyms\n");
return 1;
return err;
}
if (load_bpf_file(filename)) {
printf("%s", bpf_log_buf);
return 1;
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 */
@ -378,6 +419,12 @@ int main(int argc, char **argv)
false));
CHECK_AND_RET(test_debug_fs_uprobe((char *)argv[0], uprobe_file_offset,
true));
err = 0;
return 0;
cleanup:
for (i--; i >= 0; i--)
bpf_link__destroy(links[i]);
bpf_object__close(obj);
return err;
}