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