1// SPDX-License-Identifier: GPL-2.0
2
3#include <linux/bpf.h>
4#include <bpf/bpf_helpers.h>
5
6/* Permit pretty deep stack traces */
7#define MAX_STACK_RAWTP 100
8struct stack_trace_t {
9	int pid;
10	int kern_stack_size;
11	int user_stack_size;
12	int user_stack_buildid_size;
13	__u64 kern_stack[MAX_STACK_RAWTP];
14	__u64 user_stack[MAX_STACK_RAWTP];
15	struct bpf_stack_build_id user_stack_buildid[MAX_STACK_RAWTP];
16};
17
18struct {
19	__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
20	__uint(max_entries, 2);
21	__uint(key_size, sizeof(int));
22	__uint(value_size, sizeof(__u32));
23} perfmap SEC(".maps");
24
25struct {
26	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
27	__uint(max_entries, 1);
28	__type(key, __u32);
29	__type(value, struct stack_trace_t);
30} stackdata_map SEC(".maps");
31
32/* Allocate per-cpu space twice the needed. For the code below
33 *   usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
34 *   if (usize < 0)
35 *     return 0;
36 *   ksize = bpf_get_stack(ctx, raw_data + usize, max_len - usize, 0);
37 *
38 * If we have value_size = MAX_STACK_RAWTP * sizeof(__u64),
39 * verifier will complain that access "raw_data + usize"
40 * with size "max_len - usize" may be out of bound.
41 * The maximum "raw_data + usize" is "raw_data + max_len"
42 * and the maximum "max_len - usize" is "max_len", verifier
43 * concludes that the maximum buffer access range is
44 * "raw_data[0...max_len * 2 - 1]" and hence reject the program.
45 *
46 * Doubling the to-be-used max buffer size can fix this verifier
47 * issue and avoid complicated C programming massaging.
48 * This is an acceptable workaround since there is one entry here.
49 */
50struct {
51	__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
52	__uint(max_entries, 1);
53	__type(key, __u32);
54	__type(value, __u64[2 * MAX_STACK_RAWTP]);
55} rawdata_map SEC(".maps");
56
57SEC("raw_tracepoint/sys_enter")
58int bpf_prog1(void *ctx)
59{
60	int max_len, max_buildid_len, total_size;
61	struct stack_trace_t *data;
62	long usize, ksize;
63	void *raw_data;
64	__u32 key = 0;
65
66	data = bpf_map_lookup_elem(&stackdata_map, &key);
67	if (!data)
68		return 0;
69
70	max_len = MAX_STACK_RAWTP * sizeof(__u64);
71	max_buildid_len = MAX_STACK_RAWTP * sizeof(struct bpf_stack_build_id);
72	data->pid = bpf_get_current_pid_tgid();
73	data->kern_stack_size = bpf_get_stack(ctx, data->kern_stack,
74					      max_len, 0);
75	data->user_stack_size = bpf_get_stack(ctx, data->user_stack, max_len,
76					    BPF_F_USER_STACK);
77	data->user_stack_buildid_size = bpf_get_stack(
78		ctx, data->user_stack_buildid, max_buildid_len,
79		BPF_F_USER_STACK | BPF_F_USER_BUILD_ID);
80	bpf_perf_event_output(ctx, &perfmap, 0, data, sizeof(*data));
81
82	/* write both kernel and user stacks to the same buffer */
83	raw_data = bpf_map_lookup_elem(&rawdata_map, &key);
84	if (!raw_data)
85		return 0;
86
87	usize = bpf_get_stack(ctx, raw_data, max_len, BPF_F_USER_STACK);
88	if (usize < 0)
89		return 0;
90
91	ksize = bpf_get_stack(ctx, raw_data + usize, max_len - usize, 0);
92	if (ksize < 0)
93		return 0;
94
95	total_size = usize + ksize;
96	if (total_size > 0 && total_size <= max_len)
97		bpf_perf_event_output(ctx, &perfmap, 0, raw_data, total_size);
98
99	return 0;
100}
101
102char _license[] SEC("license") = "GPL";
103