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
8 struct 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
18 struct {
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
25 struct {
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 */
50 struct {
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
57 SEC("raw_tracepoint/sys_enter")
bpf_prog1(void * ctx)58 int 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
102 char _license[] SEC("license") = "GPL";
103
