1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (C) 2021. Huawei Technologies Co., Ltd */
3#include <linux/types.h>
4#include <linux/bpf.h>
5#include <bpf/bpf_helpers.h>
6#include <bpf/bpf_tracing.h>
7
8#define STRNCMP_STR_SZ 4096
9
10/* Will be updated by benchmark before program loading */
11const volatile unsigned int cmp_str_len = 1;
12const char target[STRNCMP_STR_SZ];
13
14long hits = 0;
15char str[STRNCMP_STR_SZ];
16
17char _license[] SEC("license") = "GPL";
18
19static __always_inline int local_strncmp(const char *s1, unsigned int sz,
20 const char *s2)
21{
22 int ret = 0;
23 unsigned int i;
24
25 for (i = 0; i < sz; i++) {
26 /* E.g. 0xff > 0x31 */
27 ret = (unsigned char)s1[i] - (unsigned char)s2[i];
28 if (ret || !s1[i])
29 break;
30 }
31
32 return ret;
33}
34
35SEC("tp/syscalls/sys_enter_getpgid")
36int strncmp_no_helper(void *ctx)
37{
38 if (local_strncmp(s1: str, sz: cmp_str_len + 1, s2: target) < 0)
39 __sync_add_and_fetch(&hits, 1);
40 return 0;
41}
42
43SEC("tp/syscalls/sys_enter_getpgid")
44int strncmp_helper(void *ctx)
45{
46 if (bpf_strncmp(str, cmp_str_len + 1, target) < 0)
47 __sync_add_and_fetch(&hits, 1);
48 return 0;
49}
50
51

source code of linux/tools/testing/selftests/bpf/progs/strncmp_bench.c