1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2020 Facebook */
3 #include "bpf_iter.h"
4 #include <bpf/bpf_helpers.h>
5 #include <bpf/bpf_tracing.h>
6
7 char _license[] SEC("license") = "GPL";
8
9 #define MAX_STACK_TRACE_DEPTH 64
10 unsigned long entries[MAX_STACK_TRACE_DEPTH] = {};
11 #define SIZE_OF_ULONG (sizeof(unsigned long))
12
13 SEC("iter/task")
dump_task_stack(struct bpf_iter__task * ctx)14 int dump_task_stack(struct bpf_iter__task *ctx)
15 {
16 struct seq_file *seq = ctx->meta->seq;
17 struct task_struct *task = ctx->task;
18 long i, retlen;
19
20 if (task == (void *)0)
21 return 0;
22
23 retlen = bpf_get_task_stack(task, entries,
24 MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0);
25 if (retlen < 0)
26 return 0;
27
28 BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid,
29 retlen / SIZE_OF_ULONG);
30 for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
31 if (retlen > i * SIZE_OF_ULONG)
32 BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
33 }
34 BPF_SEQ_PRINTF(seq, "\n");
35
36 return 0;
37 }
38
39 SEC("iter/task")
get_task_user_stacks(struct bpf_iter__task * ctx)40 int get_task_user_stacks(struct bpf_iter__task *ctx)
41 {
42 struct seq_file *seq = ctx->meta->seq;
43 struct task_struct *task = ctx->task;
44 uint64_t buf_sz = 0;
45 int64_t res;
46
47 if (task == (void *)0)
48 return 0;
49
50 res = bpf_get_task_stack(task, entries,
51 MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, BPF_F_USER_STACK);
52 if (res <= 0)
53 return 0;
54
55 buf_sz += res;
56
57 /* If the verifier doesn't refine bpf_get_task_stack res, and instead
58 * assumes res is entirely unknown, this program will fail to load as
59 * the verifier will believe that max buf_sz value allows reading
60 * past the end of entries in bpf_seq_write call
61 */
62 bpf_seq_write(seq, &entries, buf_sz);
63 return 0;
64 }
65