1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2020 Facebook */
3#include "bpf_iter.h"
4#include <bpf/bpf_helpers.h>
5
6char _license[] SEC("license") = "GPL";
7
8#define MAX_STACK_TRACE_DEPTH   64
9unsigned long entries[MAX_STACK_TRACE_DEPTH] = {};
10#define SIZE_OF_ULONG (sizeof(unsigned long))
11
12SEC("iter/task")
13int 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
38int num_user_stacks = 0;
39
40SEC("iter/task")
41int 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