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")
dump_task_stack(struct bpf_iter__task * ctx)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 SEC("iter/task")
get_task_user_stacks(struct bpf_iter__task * ctx)39 int get_task_user_stacks(struct bpf_iter__task *ctx)
40 {
41 struct seq_file *seq = ctx->meta->seq;
42 struct task_struct *task = ctx->task;
43 uint64_t buf_sz = 0;
44 int64_t res;
45
46 if (task == (void *)0)
47 return 0;
48
49 res = bpf_get_task_stack(task, entries,
50 MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, BPF_F_USER_STACK);
51 if (res <= 0)
52 return 0;
53
54 buf_sz += res;
55
56 /* If the verifier doesn't refine bpf_get_task_stack res, and instead
57 * assumes res is entirely unknown, this program will fail to load as
58 * the verifier will believe that max buf_sz value allows reading
59 * past the end of entries in bpf_seq_write call
60 */
61 bpf_seq_write(seq, &entries, buf_sz);
62 return 0;
63 }
64
