// SPDX-License-Identifier: GPL-2.0/* Copyright (c) 2020 Facebook */#include <vmlinux.h>#include <bpf/bpf_helpers.h> char _license[] SEC("license") = "GPL"; #define MAX_STACK_TRACE_DEPTH   64unsigned 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;} int num_user_stacks = 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; 	/* Only one task, the current one, should succeed */	++num_user_stacks; 	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;}