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
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