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
tasks_kfunc_map_value_lookup(struct task_struct * p)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
tasks_kfunc_map_insert(struct task_struct * p)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