1 /* SPDX-License-Identifier: GPL-2.0 */
2 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
3 
4 #ifndef _TASK_KFUNC_COMMON_H
5 #define _TASK_KFUNC_COMMON_H
6 
7 #include <errno.h>
8 #include <vmlinux.h>
9 #include <bpf/bpf_helpers.h>
10 #include <bpf/bpf_tracing.h>
11 
12 struct __tasks_kfunc_map_value {
13 	struct task_struct __kptr * task;
14 };
15 
16 struct hash_map {
17 	__uint(type, BPF_MAP_TYPE_HASH);
18 	__type(key, int);
19 	__type(value, struct __tasks_kfunc_map_value);
20 	__uint(max_entries, 1);
21 } __tasks_kfunc_map SEC(".maps");
22 
23 struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
24 void bpf_task_release(struct task_struct *p) __ksym;
25 struct task_struct *bpf_task_from_pid(s32 pid) __ksym;
26 void bpf_rcu_read_lock(void) __ksym;
27 void bpf_rcu_read_unlock(void) __ksym;
28 
29 static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
30 {
31 	s32 pid;
32 	long status;
33 
34 	status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
35 	if (status)
36 		return NULL;
37 
38 	return bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
39 }
40 
41 static inline int tasks_kfunc_map_insert(struct task_struct *p)
42 {
43 	struct __tasks_kfunc_map_value local, *v;
44 	long status;
45 	struct task_struct *acquired, *old;
46 	s32 pid;
47 
48 	status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
49 	if (status)
50 		return status;
51 
52 	local.task = NULL;
53 	status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
54 	if (status)
55 		return status;
56 
57 	v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
58 	if (!v) {
59 		bpf_map_delete_elem(&__tasks_kfunc_map, &pid);
60 		return -ENOENT;
61 	}
62 
63 	acquired = bpf_task_acquire(p);
64 	if (!acquired)
65 		return -ENOENT;
66 
67 	old = bpf_kptr_xchg(&v->task, acquired);
68 	if (old) {
69 		bpf_task_release(old);
70 		return -EEXIST;
71 	}
72 
73 	return 0;
74 }
75 
76 #endif /* _TASK_KFUNC_COMMON_H */
77