task_work.c

  1// SPDX-License-Identifier: GPL-2.0
  2/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
  3
  4#include <vmlinux.h>
  5#include <string.h>
  6#include <stdbool.h>
  7#include <bpf/bpf_helpers.h>
  8#include <bpf/bpf_tracing.h>
  9#include "bpf_misc.h"
 10#include "errno.h"
 11
 12char _license[] SEC("license") = "GPL";
 13
 14const void *user_ptr = NULL;
 15
 16struct elem {
 17	char data[128];
 18	struct bpf_task_work tw;
 19};
 20
 21struct {
 22	__uint(type, BPF_MAP_TYPE_HASH);
 23	__uint(map_flags, BPF_F_NO_PREALLOC);
 24	__uint(max_entries, 1);
 25	__type(key, int);
 26	__type(value, struct elem);
 27} hmap SEC(".maps");
 28
 29struct {
 30	__uint(type, BPF_MAP_TYPE_ARRAY);
 31	__uint(max_entries, 1);
 32	__type(key, int);
 33	__type(value, struct elem);
 34} arrmap SEC(".maps");
 35
 36struct {
 37	__uint(type, BPF_MAP_TYPE_LRU_HASH);
 38	__uint(max_entries, 1);
 39	__type(key, int);
 40	__type(value, struct elem);
 41} lrumap SEC(".maps");
 42
 43static int process_work(struct bpf_map *map, void *key, void *value)
 44{
 45	struct elem *work = value;
 46
 47	bpf_copy_from_user_str(work->data, sizeof(work->data), (const void *)user_ptr, 0);
 48	return 0;
 49}
 50
 51int key = 0;
 52
 53SEC("perf_event")
 54int oncpu_hash_map(struct pt_regs *args)
 55{
 56	struct elem empty_work = { .data = { 0 } };
 57	struct elem *work;
 58	struct task_struct *task;
 59	int err;
 60
 61	task = bpf_get_current_task_btf();
 62	err = bpf_map_update_elem(&hmap, &key, &empty_work, BPF_NOEXIST);
 63	if (err)
 64		return 0;
 65	work = bpf_map_lookup_elem(&hmap, &key);
 66	if (!work)
 67		return 0;
 68
 69	bpf_task_work_schedule_resume_impl(task, &work->tw, &hmap, process_work, NULL);
 70	return 0;
 71}
 72
 73SEC("perf_event")
 74int oncpu_array_map(struct pt_regs *args)
 75{
 76	struct elem *work;
 77	struct task_struct *task;
 78
 79	task = bpf_get_current_task_btf();
 80	work = bpf_map_lookup_elem(&arrmap, &key);
 81	if (!work)
 82		return 0;
 83	bpf_task_work_schedule_signal_impl(task, &work->tw, &arrmap, process_work, NULL);
 84	return 0;
 85}
 86
 87SEC("perf_event")
 88int oncpu_lru_map(struct pt_regs *args)
 89{
 90	struct elem empty_work = { .data = { 0 } };
 91	struct elem *work;
 92	struct task_struct *task;
 93	int err;
 94
 95	task = bpf_get_current_task_btf();
 96	work = bpf_map_lookup_elem(&lrumap, &key);
 97	if (work)
 98		return 0;
 99	err = bpf_map_update_elem(&lrumap, &key, &empty_work, BPF_NOEXIST);
100	if (err)
101		return 0;
102	work = bpf_map_lookup_elem(&lrumap, &key);
103	if (!work || work->data[0])
104		return 0;
105	bpf_task_work_schedule_resume_impl(task, &work->tw, &lrumap, process_work, NULL);
106	return 0;
107}