test_ringbuf_overwrite.c

 1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (C) 2025. Huawei Technologies Co., Ltd */
 3
 4#include <linux/bpf.h>
 5#include <bpf/bpf_helpers.h>
 6#include "bpf_misc.h"
 7
 8char _license[] SEC("license") = "GPL";
 9
10struct {
11	__uint(type, BPF_MAP_TYPE_RINGBUF);
12	__uint(map_flags, BPF_F_RB_OVERWRITE);
13} ringbuf SEC(".maps");
14
15int pid;
16
17const volatile unsigned long LEN1;
18const volatile unsigned long LEN2;
19const volatile unsigned long LEN3;
20const volatile unsigned long LEN4;
21const volatile unsigned long LEN5;
22
23long reserve1_fail = 0;
24long reserve2_fail = 0;
25long reserve3_fail = 0;
26long reserve4_fail = 0;
27long reserve5_fail = 0;
28
29unsigned long avail_data = 0;
30unsigned long ring_size = 0;
31unsigned long cons_pos = 0;
32unsigned long prod_pos = 0;
33unsigned long over_pos = 0;
34
35SEC("fentry/" SYS_PREFIX "sys_getpgid")
36int test_overwrite_ringbuf(void *ctx)
37{
38	char *rec1, *rec2, *rec3, *rec4, *rec5;
39	int cur_pid = bpf_get_current_pid_tgid() >> 32;
40
41	if (cur_pid != pid)
42		return 0;
43
44	rec1 = bpf_ringbuf_reserve(&ringbuf, LEN1, 0);
45	if (!rec1) {
46		reserve1_fail = 1;
47		return 0;
48	}
49
50	rec2 = bpf_ringbuf_reserve(&ringbuf, LEN2, 0);
51	if (!rec2) {
52		bpf_ringbuf_discard(rec1, 0);
53		reserve2_fail = 1;
54		return 0;
55	}
56
57	rec3 = bpf_ringbuf_reserve(&ringbuf, LEN3, 0);
58	/* expect failure */
59	if (!rec3) {
60		reserve3_fail = 1;
61	} else {
62		bpf_ringbuf_discard(rec1, 0);
63		bpf_ringbuf_discard(rec2, 0);
64		bpf_ringbuf_discard(rec3, 0);
65		return 0;
66	}
67
68	rec4 = bpf_ringbuf_reserve(&ringbuf, LEN4, 0);
69	if (!rec4) {
70		reserve4_fail = 1;
71		bpf_ringbuf_discard(rec1, 0);
72		bpf_ringbuf_discard(rec2, 0);
73		return 0;
74	}
75
76	bpf_ringbuf_submit(rec1, 0);
77	bpf_ringbuf_submit(rec2, 0);
78	bpf_ringbuf_submit(rec4, 0);
79
80	rec5 = bpf_ringbuf_reserve(&ringbuf, LEN5, 0);
81	if (!rec5) {
82		reserve5_fail = 1;
83		return 0;
84	}
85
86	for (int i = 0; i < LEN3; i++)
87		rec5[i] = 0xdd;
88
89	bpf_ringbuf_submit(rec5, 0);
90
91	ring_size = bpf_ringbuf_query(&ringbuf, BPF_RB_RING_SIZE);
92	avail_data = bpf_ringbuf_query(&ringbuf, BPF_RB_AVAIL_DATA);
93	cons_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_CONS_POS);
94	prod_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_PROD_POS);
95	over_pos = bpf_ringbuf_query(&ringbuf, BPF_RB_OVERWRITE_POS);
96
97	return 0;
98}