tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1// SPDX-License-Identifier: GPL-2.0-only
2
3#include "vmlinux.h"
4#include <bpf/bpf_tracing.h>
5#include <bpf/bpf_helpers.h>
6
7char _license[] SEC("license") = "GPL";
8
9#define EPERM 1 /* Operation not permitted */
10
11/* From include/linux/mm.h. */
12#define FMODE_WRITE 0x2
13
14struct map;
15
16struct {
17 __uint(type, BPF_MAP_TYPE_ARRAY);
18 __type(key, __u32);
19 __type(value, __u32);
20 __uint(max_entries, 1);
21} prot_status_map SEC(".maps");
22
23struct {
24 __uint(type, BPF_MAP_TYPE_HASH);
25 __type(key, __u32);
26 __type(value, __u32);
27 __uint(max_entries, 3);
28} prot_map SEC(".maps");
29
30struct {
31 __uint(type, BPF_MAP_TYPE_HASH);
32 __type(key, __u32);
33 __type(value, __u32);
34 __uint(max_entries, 3);
35} not_prot_map SEC(".maps");
36
37SEC("fmod_ret/security_bpf_map")
38int BPF_PROG(fmod_bpf_map, struct bpf_map *map, int fmode)
39{
40 __u32 key = 0;
41 __u32 *status_ptr = bpf_map_lookup_elem(&prot_status_map, &key);
42
43 if (!status_ptr || !*status_ptr)
44 return 0;
45
46 if (map == &prot_map) {
47 /* Allow read-only access */
48 if (fmode & FMODE_WRITE)
49 return -EPERM;
50 }
51
52 return 0;
53}
54
55/*
56 * This program keeps references to maps. This is needed to prevent
57 * optimizing them out.
58 */
59SEC("fentry/bpf_fentry_test1")
60int BPF_PROG(fentry_dummy1, int a)
61{
62 __u32 key = 0;
63 __u32 val1 = a;
64 __u32 val2 = a + 1;
65
66 bpf_map_update_elem(&prot_map, &key, &val1, BPF_ANY);
67 bpf_map_update_elem(¬_prot_map, &key, &val2, BPF_ANY);
68 return 0;
69}