1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
3
4 #include "bpf_iter.h"
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_tracing.h>
7 #include "bpf_misc.h"
8
9 char _license[] SEC("license") = "GPL";
10
11 struct {
12 __uint(type, BPF_MAP_TYPE_CGRP_STORAGE);
13 __uint(map_flags, BPF_F_NO_PREALLOC);
14 __type(key, int);
15 __type(value, long);
16 } map_a SEC(".maps");
17
18 __u32 target_pid;
19 __u64 cgroup_id;
20
21 void bpf_rcu_read_lock(void) __ksym;
22 void bpf_rcu_read_unlock(void) __ksym;
23
24 SEC("?iter.s/cgroup")
cgroup_iter(struct bpf_iter__cgroup * ctx)25 int cgroup_iter(struct bpf_iter__cgroup *ctx)
26 {
27 struct seq_file *seq = ctx->meta->seq;
28 struct cgroup *cgrp = ctx->cgroup;
29 long *ptr;
30
31 if (cgrp == NULL)
32 return 0;
33
34 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
35 BPF_LOCAL_STORAGE_GET_F_CREATE);
36 if (ptr)
37 cgroup_id = cgrp->kn->id;
38 return 0;
39 }
40
41 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
no_rcu_lock(void * ctx)42 int no_rcu_lock(void *ctx)
43 {
44 struct task_struct *task;
45 struct cgroup *cgrp;
46 long *ptr;
47
48 task = bpf_get_current_task_btf();
49 if (task->pid != target_pid)
50 return 0;
51
52 /* ptr_to_btf_id semantics. should work. */
53 cgrp = task->cgroups->dfl_cgrp;
54 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0,
55 BPF_LOCAL_STORAGE_GET_F_CREATE);
56 if (ptr)
57 cgroup_id = cgrp->kn->id;
58 return 0;
59 }
60
61 SEC("?fentry.s/" SYS_PREFIX "sys_getpgid")
yes_rcu_lock(void * ctx)62 int yes_rcu_lock(void *ctx)
63 {
64 struct task_struct *task;
65 struct cgroup *cgrp;
66 long *ptr;
67
68 task = bpf_get_current_task_btf();
69 if (task->pid != target_pid)
70 return 0;
71
72 bpf_rcu_read_lock();
73 cgrp = task->cgroups->dfl_cgrp;
74 /* cgrp is untrusted and cannot pass to bpf_cgrp_storage_get() helper. */
75 ptr = bpf_cgrp_storage_get(&map_a, cgrp, 0, BPF_LOCAL_STORAGE_GET_F_CREATE);
76 if (ptr)
77 cgroup_id = cgrp->kn->id;
78 bpf_rcu_read_unlock();
79 return 0;
80 }
81