[bpf-next v2 1/5] samples/bpf: use kyscall instead of kprobe in syscall tracing program

Daniel T. Lee
2022-12-20T11:59:43Z

Syscall tracing using kprobe is quite unstable. Since it uses the exact
name of the kernel function, the program might broke due to the rename
of a function. The problem can also be caused by a changes in the
arguments of the function to which the kprobe connects.

In this commit, ksyscall is used instead of kprobe. By using ksyscall,
libbpf will detect the appropriate kernel function name.
(e.g. sys_write -> __s390_sys_write). This eliminates the need to worry
about which wrapper function to attach in order to parse arguments.

In addition, ksyscall provides more fine method with attaching system
call, the coarse SYSCALL helper at trace_common.h can be removed.

Signed-off-by: Daniel T. Lee <danieltimlee@gmail.com>
---
samples/bpf/map_perf_test_kern.c | 17 ++++++++---------
.../bpf/test_current_task_under_cgroup_kern.c | 3 +--
samples/bpf/test_map_in_map_kern.c | 1 -
samples/bpf/test_probe_write_user_kern.c | 3 +--
samples/bpf/trace_common.h | 13 -------------
samples/bpf/trace_output_kern.c | 3 +--
samples/bpf/tracex2_kern.c | 3 +--
7 files changed, 12 insertions(+), 31 deletions(-)
delete mode 100644 samples/bpf/trace_common.h

diff --git a/samples/bpf/map_perf_test_kern.c b/samples/bpf/map_perf_test_kern.c
index 7342c5b2f278..874e2f7e3d5d 100644
--- a/samples/bpf/map_perf_test_kern.c
+++ b/samples/bpf/map_perf_test_kern.c
@@ -11,7 +11,6 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
-#include "trace_common.h"

#define MAX_ENTRIES 1000
#define MAX_NR_CPUS 1024
@@ -102,7 +101,7 @@ struct {
__uint(max_entries, MAX_ENTRIES);
} lru_hash_lookup_map SEC(".maps");

-SEC("kprobe/" SYSCALL(sys_getuid))
+SEC("ksyscall/getuid")
int stress_hmap(struct pt_regs *ctx)
{
u32 key = bpf_get_current_pid_tgid();
@@ -120,7 +119,7 @@ int stress_hmap(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_geteuid))
+SEC("ksyscall/geteuid")
int stress_percpu_hmap(struct pt_regs *ctx)
{
u32 key = bpf_get_current_pid_tgid();
@@ -137,7 +136,7 @@ int stress_percpu_hmap(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_getgid))
+SEC("ksyscall/getgid")
int stress_hmap_alloc(struct pt_regs *ctx)
{
u32 key = bpf_get_current_pid_tgid();
@@ -154,7 +153,7 @@ int stress_hmap_alloc(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_getegid))
+SEC("ksyscall/getegid")
int stress_percpu_hmap_alloc(struct pt_regs *ctx)
{
u32 key = bpf_get_current_pid_tgid();
@@ -171,7 +170,7 @@ int stress_percpu_hmap_alloc(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_connect))
+SEC("ksyscall/connect")
int stress_lru_hmap_alloc(struct pt_regs *ctx)
{
struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);
@@ -251,7 +250,7 @@ int stress_lru_hmap_alloc(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_gettid))
+SEC("ksyscall/gettid")
int stress_lpm_trie_map_alloc(struct pt_regs *ctx)
{
union {
@@ -273,7 +272,7 @@ int stress_lpm_trie_map_alloc(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_getpgid))
+SEC("ksyscall/getpgid")
int stress_hash_map_lookup(struct pt_regs *ctx)
{
u32 key = 1, i;
@@ -286,7 +285,7 @@ int stress_hash_map_lookup(struct pt_regs *ctx)
return 0;
}

-SEC("kprobe/" SYSCALL(sys_getppid))
+SEC("ksyscall/getppid")
int stress_array_map_lookup(struct pt_regs *ctx)
{
u32 key = 1, i;
diff --git a/samples/bpf/test_current_task_under_cgroup_kern.c b/samples/bpf/test_current_task_under_cgroup_kern.c
index fbd43e2bb4d3..541fc861b984 100644
--- a/samples/bpf/test_current_task_under_cgroup_kern.c
+++ b/samples/bpf/test_current_task_under_cgroup_kern.c
@@ -10,7 +10,6 @@
#include <linux/version.h>
#include <bpf/bpf_helpers.h>
#include <uapi/linux/utsname.h>
-#include "trace_common.h"

struct {
__uint(type, BPF_MAP_TYPE_CGROUP_ARRAY);
@@ -27,7 +26,7 @@ struct {
} perf_map SEC(".maps");

/* Writes the last PID that called sync to a map at index 0 */
-SEC("kprobe/" SYSCALL(sys_sync))
+SEC("ksyscall/sync")
int bpf_prog1(struct pt_regs *ctx)
{
u64 pid = bpf_get_current_pid_tgid();
diff --git a/samples/bpf/test_map_in_map_kern.c b/samples/bpf/test_map_in_map_kern.c
index b0200c8eac09..0e17f9ade5c5 100644
--- a/samples/bpf/test_map_in_map_kern.c
+++ b/samples/bpf/test_map_in_map_kern.c
@@ -13,7 +13,6 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
-#include "trace_common.h"

#define MAX_NR_PORTS 65536

diff --git a/samples/bpf/test_probe_write_user_kern.c b/samples/bpf/test_probe_write_user_kern.c
index 220a96438d75..d60cabaaf753 100644
--- a/samples/bpf/test_probe_write_user_kern.c
+++ b/samples/bpf/test_probe_write_user_kern.c
@@ -11,7 +11,6 @@
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
#include <bpf/bpf_core_read.h>
-#include "trace_common.h"

struct {
__uint(type, BPF_MAP_TYPE_HASH);
@@ -28,7 +27,7 @@ struct {
* This example sits on a syscall, and the syscall ABI is relatively stable
* of course, across platforms, and over time, the ABI may change.
*/
-SEC("kprobe/" SYSCALL(sys_connect))
+SEC("ksyscall/connect")
int bpf_prog1(struct pt_regs *ctx)
{
struct pt_regs *real_regs = (struct pt_regs *)PT_REGS_PARM1_CORE(ctx);
diff --git a/samples/bpf/trace_common.h b/samples/bpf/trace_common.h
deleted file mode 100644
index 8cb5400aed1f..000000000000
--- a/samples/bpf/trace_common.h
+++ /dev/null
@@ -1,13 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#ifndef __TRACE_COMMON_H
-#define __TRACE_COMMON_H
-
-#ifdef __x86_64__
-#define SYSCALL(SYS) "__x64_" __stringify(SYS)
-#elif defined(__s390x__)
-#define SYSCALL(SYS) "__s390x_" __stringify(SYS)
-#else
-#define SYSCALL(SYS) __stringify(SYS)
-#endif
-
-#endif
diff --git a/samples/bpf/trace_output_kern.c b/samples/bpf/trace_output_kern.c
index b64815af0943..a481abf8c4c5 100644
--- a/samples/bpf/trace_output_kern.c
+++ b/samples/bpf/trace_output_kern.c
@@ -2,7 +2,6 @@
#include <linux/version.h>
#include <uapi/linux/bpf.h>
#include <bpf/bpf_helpers.h>
-#include "trace_common.h"

struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
@@ -11,7 +10,7 @@ struct {
__uint(max_entries, 2);
} my_map SEC(".maps");

-SEC("kprobe/" SYSCALL(sys_write))
+SEC("ksyscall/write")
int bpf_prog1(struct pt_regs *ctx)
{
struct S {
diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
index 93e0b7680b4f..82091facb83c 100644
--- a/samples/bpf/tracex2_kern.c
+++ b/samples/bpf/tracex2_kern.c
@@ -10,7 +10,6 @@
#include <uapi/linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
-#include "trace_common.h"

struct {
__uint(type, BPF_MAP_TYPE_HASH);
@@ -78,7 +77,7 @@ struct {
__uint(max_entries, 1024);
} my_hist_map SEC(".maps");

-SEC("kprobe/" SYSCALL(sys_write))
+SEC("ksyscall/write")
int bpf_prog3(struct pt_regs *ctx)
{
long write_size = PT_REGS_PARM3(ctx);
--
2.34.1