1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <vmlinux.h>
4 #include <bpf/bpf_tracing.h>
5 #include <bpf/bpf_helpers.h>
6 
7 struct map_elem {
8 	struct bpf_timer timer;
9 	struct bpf_spin_lock lock;
10 };
11 
12 struct {
13 	__uint(type, BPF_MAP_TYPE_ARRAY);
14 	__uint(max_entries, 1);
15 	__type(key, int);
16 	__type(value, struct map_elem);
17 } amap SEC(".maps");
18 
19 struct {
20 	__uint(type, BPF_MAP_TYPE_HASH);
21 	__uint(max_entries, 1);
22 	__type(key, int);
23 	__type(value, struct map_elem);
24 } hmap SEC(".maps");
25 
26 int pid = 0;
27 int crash_map = 0; /* 0 for amap, 1 for hmap */
28 
29 SEC("fentry/do_nanosleep")
30 int sys_enter(void *ctx)
31 {
32 	struct map_elem *e, value = {};
33 	void *map = crash_map ? (void *)&hmap : (void *)&amap;
34 
35 	if (bpf_get_current_task_btf()->tgid != pid)
36 		return 0;
37 
38 	*(void **)&value = (void *)0xdeadcaf3;
39 
40 	bpf_map_update_elem(map, &(int){0}, &value, 0);
41 	/* For array map, doing bpf_map_update_elem will do a
42 	 * check_and_free_timer_in_array, which will trigger the crash if timer
43 	 * pointer was overwritten, for hmap we need to use bpf_timer_cancel.
44 	 */
45 	if (crash_map == 1) {
46 		e = bpf_map_lookup_elem(map, &(int){0});
47 		if (!e)
48 			return 0;
49 		bpf_timer_cancel(&e->timer);
50 	}
51 	return 0;
52 }
53 
54 char _license[] SEC("license") = "GPL";
55