1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* Copyright (c) 2021 Google */ |
3 | |
4 | #include "vmlinux.h" |
5 | |
6 | #include <bpf/bpf_helpers.h> |
7 | |
8 | extern const int bpf_prog_active __ksym; /* int type global var. */ |
9 | |
10 | SEC("raw_tp/sys_enter" ) |
11 | int handler1(const void *ctx) |
12 | { |
13 | int *active; |
14 | __u32 cpu; |
15 | |
16 | cpu = bpf_get_smp_processor_id(); |
17 | active = (int *)bpf_per_cpu_ptr(&bpf_prog_active, cpu); |
18 | if (active) { |
19 | /* Kernel memory obtained from bpf_{per,this}_cpu_ptr |
20 | * is read-only, should _not_ pass verification. |
21 | */ |
22 | /* WRITE_ONCE */ |
23 | *(volatile int *)active = -1; |
24 | } |
25 | |
26 | return 0; |
27 | } |
28 | |
29 | __noinline int write_active(int *p) |
30 | { |
31 | return p ? (*p = 42) : 0; |
32 | } |
33 | |
34 | SEC("raw_tp/sys_enter" ) |
35 | int handler2(const void *ctx) |
36 | { |
37 | int *active; |
38 | |
39 | active = bpf_this_cpu_ptr(&bpf_prog_active); |
40 | write_active(active); |
41 | return 0; |
42 | } |
43 | |
44 | char _license[] SEC("license" ) = "GPL" ; |
45 | |