1c7568114SSong Liu // SPDX-License-Identifier: GPL-2.0
2c7568114SSong Liu /* Copyright (c) 2020 Facebook */
3c7568114SSong Liu #include "bpf_iter.h"
4c7568114SSong Liu #include <bpf/bpf_helpers.h>
5c7568114SSong Liu
6c7568114SSong Liu char _license[] SEC("license") = "GPL";
7c7568114SSong Liu
8c7568114SSong Liu #define MAX_STACK_TRACE_DEPTH 64
99ff79af3SSong Liu unsigned long entries[MAX_STACK_TRACE_DEPTH] = {};
10c7568114SSong Liu #define SIZE_OF_ULONG (sizeof(unsigned long))
11c7568114SSong Liu
12c7568114SSong Liu SEC("iter/task")
dump_task_stack(struct bpf_iter__task * ctx)13c7568114SSong Liu int dump_task_stack(struct bpf_iter__task *ctx)
14c7568114SSong Liu {
15c7568114SSong Liu struct seq_file *seq = ctx->meta->seq;
16c7568114SSong Liu struct task_struct *task = ctx->task;
17c7568114SSong Liu long i, retlen;
18c7568114SSong Liu
19c7568114SSong Liu if (task == (void *)0)
20c7568114SSong Liu return 0;
21c7568114SSong Liu
22c7568114SSong Liu retlen = bpf_get_task_stack(task, entries,
23c7568114SSong Liu MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0);
24c7568114SSong Liu if (retlen < 0)
25c7568114SSong Liu return 0;
26c7568114SSong Liu
27c7568114SSong Liu BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid,
28c7568114SSong Liu retlen / SIZE_OF_ULONG);
29c7568114SSong Liu for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
30c7568114SSong Liu if (retlen > i * SIZE_OF_ULONG)
31c7568114SSong Liu BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
32c7568114SSong Liu }
33c7568114SSong Liu BPF_SEQ_PRINTF(seq, "\n");
34c7568114SSong Liu
35c7568114SSong Liu return 0;
36c7568114SSong Liu }
37c77cec5cSDave Marchevsky
38*3db79d21SJordan Rome int num_user_stacks = 0;
39*3db79d21SJordan Rome
40c77cec5cSDave Marchevsky SEC("iter/task")
get_task_user_stacks(struct bpf_iter__task * ctx)41c77cec5cSDave Marchevsky int get_task_user_stacks(struct bpf_iter__task *ctx)
42c77cec5cSDave Marchevsky {
43c77cec5cSDave Marchevsky struct seq_file *seq = ctx->meta->seq;
44c77cec5cSDave Marchevsky struct task_struct *task = ctx->task;
45c77cec5cSDave Marchevsky uint64_t buf_sz = 0;
46c77cec5cSDave Marchevsky int64_t res;
47c77cec5cSDave Marchevsky
48c77cec5cSDave Marchevsky if (task == (void *)0)
49c77cec5cSDave Marchevsky return 0;
50c77cec5cSDave Marchevsky
51c77cec5cSDave Marchevsky res = bpf_get_task_stack(task, entries,
52c77cec5cSDave Marchevsky MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, BPF_F_USER_STACK);
53c77cec5cSDave Marchevsky if (res <= 0)
54c77cec5cSDave Marchevsky return 0;
55c77cec5cSDave Marchevsky
56*3db79d21SJordan Rome /* Only one task, the current one, should succeed */
57*3db79d21SJordan Rome ++num_user_stacks;
58*3db79d21SJordan Rome
59c77cec5cSDave Marchevsky buf_sz += res;
60c77cec5cSDave Marchevsky
61c77cec5cSDave Marchevsky /* If the verifier doesn't refine bpf_get_task_stack res, and instead
62c77cec5cSDave Marchevsky * assumes res is entirely unknown, this program will fail to load as
63c77cec5cSDave Marchevsky * the verifier will believe that max buf_sz value allows reading
64c77cec5cSDave Marchevsky * past the end of entries in bpf_seq_write call
65c77cec5cSDave Marchevsky */
66c77cec5cSDave Marchevsky bpf_seq_write(seq, &entries, buf_sz);
67c77cec5cSDave Marchevsky return 0;
68c77cec5cSDave Marchevsky }
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