tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c

   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 SEC("iter/task")
  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 }