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 {
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 struct task_struct *bpf_task_from_vpid(s32 vpid) __ksym;
27 void bpf_rcu_read_lock(void) __ksym;
28 void bpf_rcu_read_unlock(void) __ksym;
29
tasks_kfunc_map_value_lookup(struct task_struct * p)30 static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
31 {
32 s32 pid;
33 long status;
34
35 status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
36 if (status)
37 return NULL;
38
39 return bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
40 }
41
tasks_kfunc_map_insert(struct task_struct * p)42 static inline int tasks_kfunc_map_insert(struct task_struct *p)
43 {
44 struct __tasks_kfunc_map_value local, *v;
45 long status;
46 struct task_struct *acquired, *old;
47 s32 pid;
48
49 status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
50 if (status)
51 return status;
52
53 local.task = NULL;
54 status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
55 if (status)
56 return status;
57
58 v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
59 if (!v) {
60 bpf_map_delete_elem(&__tasks_kfunc_map, &pid);
61 return -ENOENT;
62 }
63
64 acquired = bpf_task_acquire(p);
65 if (!acquired)
66 return -ENOENT;
67
68 old = bpf_kptr_xchg(&v->task, acquired);
69 if (old) {
70 bpf_task_release(old);
71 return -EEXIST;
72 }
73
74 return 0;
75 }
76
77 #endif /* _TASK_KFUNC_COMMON_H */
78