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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2020 Facebook */
#include "bpf_iter.h"
#include <bpf/bpf_helpers.h>
char _license[] SEC("license") = "GPL";
#define MAX_STACK_TRACE_DEPTH 64
unsigned long entries[MAX_STACK_TRACE_DEPTH] = {};
#define SIZE_OF_ULONG (sizeof(unsigned long))
SEC("iter/task")
int dump_task_stack(struct bpf_iter__task *ctx)
{
struct seq_file *seq = ctx->meta->seq;
struct task_struct *task = ctx->task;
long i, retlen;
if (task == (void *)0)
return 0;
retlen = bpf_get_task_stack(task, entries,
MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0);
if (retlen < 0)
return 0;
BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid,
retlen / SIZE_OF_ULONG);
for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) {
if (retlen > i * SIZE_OF_ULONG)
BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]);
}
BPF_SEQ_PRINTF(seq, "\n");
return 0;
}
SEC("iter/task")
int get_task_user_stacks(struct bpf_iter__task *ctx)
{
struct seq_file *seq = ctx->meta->seq;
struct task_struct *task = ctx->task;
uint64_t buf_sz = 0;
int64_t res;
if (task == (void *)0)
return 0;
res = bpf_get_task_stack(task, entries,
MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, BPF_F_USER_STACK);
if (res <= 0)
return 0;
buf_sz += res;
/* If the verifier doesn't refine bpf_get_task_stack res, and instead
* assumes res is entirely unknown, this program will fail to load as
* the verifier will believe that max buf_sz value allows reading
* past the end of entries in bpf_seq_write call
*/
bpf_seq_write(seq, &entries, buf_sz);
return 0;
}
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