1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* Copyright (c) 2020 Facebook */ |
3 | #include "bpf_iter.h" |
4 | #include <bpf/bpf_helpers.h> |
5 | |
6 | char _license[] SEC("license" ) = "GPL" ; |
7 | |
8 | #define MAX_STACK_TRACE_DEPTH 64 |
9 | unsigned long entries[MAX_STACK_TRACE_DEPTH] = {}; |
10 | #define SIZE_OF_ULONG (sizeof(unsigned long)) |
11 | |
12 | SEC("iter/task" ) |
13 | int dump_task_stack(struct bpf_iter__task *ctx) |
14 | { |
15 | struct seq_file *seq = ctx->meta->seq; |
16 | struct task_struct *task = ctx->task; |
17 | long i, retlen; |
18 | |
19 | if (task == (void *)0) |
20 | return 0; |
21 | |
22 | retlen = bpf_get_task_stack(task, entries, |
23 | MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0); |
24 | if (retlen < 0) |
25 | return 0; |
26 | |
27 | BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n" , task->pid, |
28 | retlen / SIZE_OF_ULONG); |
29 | for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) { |
30 | if (retlen > i * SIZE_OF_ULONG) |
31 | BPF_SEQ_PRINTF(seq, "[<0>] %pB\n" , (void *)entries[i]); |
32 | } |
33 | BPF_SEQ_PRINTF(seq, "\n" ); |
34 | |
35 | return 0; |
36 | } |
37 | |
38 | int num_user_stacks = 0; |
39 | |
40 | SEC("iter/task" ) |
41 | int get_task_user_stacks(struct bpf_iter__task *ctx) |
42 | { |
43 | struct seq_file *seq = ctx->meta->seq; |
44 | struct task_struct *task = ctx->task; |
45 | uint64_t buf_sz = 0; |
46 | int64_t res; |
47 | |
48 | if (task == (void *)0) |
49 | return 0; |
50 | |
51 | res = bpf_get_task_stack(task, entries, |
52 | MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, BPF_F_USER_STACK); |
53 | if (res <= 0) |
54 | return 0; |
55 | |
56 | /* Only one task, the current one, should succeed */ |
57 | ++num_user_stacks; |
58 | |
59 | buf_sz += res; |
60 | |
61 | /* If the verifier doesn't refine bpf_get_task_stack res, and instead |
62 | * assumes res is entirely unknown, this program will fail to load as |
63 | * the verifier will believe that max buf_sz value allows reading |
64 | * past the end of entries in bpf_seq_write call |
65 | */ |
66 | bpf_seq_write(seq, &entries, buf_sz); |
67 | return 0; |
68 | } |
69 | |