On 5/12/20 7:43 AM, Daniel T. Lee wrote:
Currently, the kprobe BPF program attachment method for bpf_load is
quite old. The implementation of bpf_load "directly" controls and
manages(create, delete) the kprobe events of DEBUGFS. On the other hand,
using using the libbpf automatically manages the kprobe event.
(under bpf_link interface)
By calling bpf_program__attach(_kprobe) in libbpf, the corresponding
kprobe is created and the BPF program will be attached to this kprobe.
To remove this, by simply invoking bpf_link__destroy will clean up the
event.
This commit refactors kprobe tracing programs (tracex{1~7}_user.c) with
libbpf using bpf_link interface and bpf_program__attach.
tracex2_kern.c, which tracks system calls (sys_*), has been modified to
append prefix depending on architecture.
Signed-off-by: Daniel T. Lee <danieltimlee@xxxxxxxxx>
---
samples/bpf/Makefile | 12 +++----
samples/bpf/tracex1_user.c | 41 ++++++++++++++++++++----
samples/bpf/tracex2_kern.c | 8 ++++-
samples/bpf/tracex2_user.c | 55 ++++++++++++++++++++++++++------
samples/bpf/tracex3_user.c | 65 ++++++++++++++++++++++++++++----------
samples/bpf/tracex4_user.c | 55 +++++++++++++++++++++++++-------
samples/bpf/tracex6_user.c | 53 +++++++++++++++++++++++++++----
samples/bpf/tracex7_user.c | 43 ++++++++++++++++++++-----
8 files changed, 268 insertions(+), 64 deletions(-)
diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 424f6fe7ce38..4c91e5914329 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -64,13 +64,13 @@ fds_example-objs := fds_example.o
sockex1-objs := sockex1_user.o
sockex2-objs := sockex2_user.o
sockex3-objs := bpf_load.o sockex3_user.o
-tracex1-objs := bpf_load.o tracex1_user.o $(TRACE_HELPERS)
-tracex2-objs := bpf_load.o tracex2_user.o
-tracex3-objs := bpf_load.o tracex3_user.o
-tracex4-objs := bpf_load.o tracex4_user.o
+tracex1-objs := tracex1_user.o $(TRACE_HELPERS)
+tracex2-objs := tracex2_user.o
+tracex3-objs := tracex3_user.o
+tracex4-objs := tracex4_user.o
tracex5-objs := bpf_load.o tracex5_user.o $(TRACE_HELPERS)
-tracex6-objs := bpf_load.o tracex6_user.o
-tracex7-objs := bpf_load.o tracex7_user.o
+tracex6-objs := tracex6_user.o
+tracex7-objs := tracex7_user.o
test_probe_write_user-objs := bpf_load.o test_probe_write_user_user.o
trace_output-objs := bpf_load.o trace_output_user.o $(TRACE_HELPERS)
lathist-objs := bpf_load.o lathist_user.o
diff --git a/samples/bpf/tracex1_user.c b/samples/bpf/tracex1_user.c
index 55fddbd08702..1b15ab98f7d3 100644
--- a/samples/bpf/tracex1_user.c
+++ b/samples/bpf/tracex1_user.c
@@ -1,21 +1,45 @@
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
-#include <linux/bpf.h>
#include <unistd.h>
-#include <bpf/bpf.h>
-#include "bpf_load.h"
+#include <bpf/libbpf.h>
#include "trace_helpers.h"
+#define __must_check
This is not very user friendly.
Maybe not including linux/err.h and
use libbpf API libbpf_get_error() instead?
+#include <linux/err.h>
+
int main(int ac, char **argv)
{
- FILE *f;
+ struct bpf_link *link = NULL;
+ struct bpf_program *prog;
+ struct bpf_object *obj;
char filename[256];
+ FILE *f;
snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
+ obj = bpf_object__open_file(filename, NULL);
+ if (IS_ERR(obj)) {
+ fprintf(stderr, "ERROR: opening BPF object file failed\n");
+ obj = NULL;
+ goto cleanup;
You do not need to goto cleanup, directly return 0 is okay here.
The same for other files in this patch.
+ }
+
+ prog = bpf_object__find_program_by_name(obj, "bpf_prog1");
+ if (!prog) {
+ fprintf(stderr, "ERROR: finding a prog in obj file failed\n");
+ goto cleanup;
+ }
+
+ /* load BPF program */
+ if (bpf_object__load(obj)) {
+ fprintf(stderr, "ERROR: loading BPF object file failed\n");
+ goto cleanup;
+ }
- if (load_bpf_file(filename)) {
- printf("%s", bpf_log_buf);
- return 1;
+ link = bpf_program__attach(prog);
+ if (IS_ERR(link)) {
+ fprintf(stderr, "ERROR: bpf_program__attach failed\n");
+ link = NULL;
+ goto cleanup;
}
f = popen("taskset 1 ping -c5 localhost", "r");
@@ -23,5 +47,8 @@ int main(int ac, char **argv)
read_trace_pipe();
+cleanup:
+ bpf_link__destroy(link);
+ bpf_object__close(obj);
Typically in kernel, we do multiple labels for such cases
like
destroy_link:
bpf_link__destroy(link);
close_object:
bpf_object__close(obj);
The error path in the main() function jumps to proper label.
This is more clean and less confusion.
The same for other cases in this file.
return 0;
}
diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
index d865bb309bcb..ff5d00916733 100644
--- a/samples/bpf/tracex2_kern.c
+++ b/samples/bpf/tracex2_kern.c
@@ -11,6 +11,12 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
+#ifdef __x86_64__
+#define SYSCALL "__x64_"
+#else
+#define SYSCALL
+#endif
See test_progs.h, one more case to handle:
#ifdef __x86_64__
#define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"
#elif defined(__s390x__)
#define SYS_NANOSLEEP_KPROBE_NAME "__s390x_sys_nanosleep"
#else
#define SYS_NANOSLEEP_KPROBE_NAME "sys_nanosleep"
#endif
+
struct bpf_map_def SEC("maps") my_map = {
.type = BPF_MAP_TYPE_HASH,
.key_size = sizeof(long),
@@ -77,7 +83,7 @@ struct bpf_map_def SEC("maps") my_hist_map = {
.max_entries = 1024,
};
-SEC("kprobe/sys_write")
+SEC("kprobe/" SYSCALL "sys_write")
int bpf_prog3(struct pt_regs *ctx)
{
long write_size = PT_REGS_PARM3(ctx);
[...]
