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") 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") 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