1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3
4 #include <linux/bpf.h>
5 #define BPF_NO_GLOBAL_DATA
6 #include <bpf/bpf_helpers.h>
7
8 char LICENSE[] SEC("license") = "GPL";
9
10 struct {
11 __uint(type, BPF_MAP_TYPE_ARRAY);
12 __type(key, int);
13 __type(value, int);
14 __uint(max_entries, 1);
15 } my_pid_map SEC(".maps");
16
17 struct {
18 __uint(type, BPF_MAP_TYPE_ARRAY);
19 __type(key, int);
20 __type(value, int);
21 __uint(max_entries, 1);
22 } res_map SEC(".maps");
23
24 volatile int my_pid_var = 0;
25 volatile int res_var = 0;
26
27 SEC("tp/raw_syscalls/sys_enter")
handle_legacy(void * ctx)28 int handle_legacy(void *ctx)
29 {
30 int zero = 0, *my_pid, cur_pid, *my_res;
31
32 my_pid = bpf_map_lookup_elem(&my_pid_map, &zero);
33 if (!my_pid)
34 return 1;
35
36 cur_pid = bpf_get_current_pid_tgid() >> 32;
37 if (cur_pid != *my_pid)
38 return 1;
39
40 my_res = bpf_map_lookup_elem(&res_map, &zero);
41 if (!my_res)
42 return 1;
43
44 if (*my_res == 0)
45 /* use bpf_printk() in combination with BPF_NO_GLOBAL_DATA to
46 * force .rodata.str1.1 section that previously caused
47 * problems on old kernels due to libbpf always tried to
48 * create a global data map for it
49 */
50 bpf_printk("Legacy-case bpf_printk test, pid %d\n", cur_pid);
51 *my_res = 1;
52
53 return *my_res;
54 }
55
56 SEC("tp/raw_syscalls/sys_enter")
handle_modern(void * ctx)57 int handle_modern(void *ctx)
58 {
59 int cur_pid;
60
61 cur_pid = bpf_get_current_pid_tgid() >> 32;
62 if (cur_pid != my_pid_var)
63 return 1;
64
65 if (res_var == 0)
66 /* we need bpf_printk() to validate libbpf logic around unused
67 * global maps and legacy kernels; see comment in handle_legacy()
68 */
69 bpf_printk("Modern-case bpf_printk test, pid %d\n", cur_pid);
70 res_var = 1;
71
72 return res_var;
73 }
74
