// SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2021 Facebook */ #include <linux/bpf.h> #define BPF_NO_GLOBAL_DATA #include <bpf/bpf_helpers.h> char LICENSE[] SEC("license") = "GPL"; struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(key, int); __type(value, int); __uint(max_entries, 1); } my_pid_map SEC(".maps"); struct { __uint(type, BPF_MAP_TYPE_ARRAY); __type(key, int); __type(value, int); __uint(max_entries, 1); } res_map SEC(".maps"); volatile int my_pid_var = 0; volatile int res_var = 0; SEC("tp/raw_syscalls/sys_enter") int handle_legacy(void *ctx) { int zero = 0, *my_pid, cur_pid, *my_res; my_pid = bpf_map_lookup_elem(&my_pid_map, &zero); if (!my_pid) return 1; cur_pid = bpf_get_current_pid_tgid() >> 32; if (cur_pid != *my_pid) return 1; my_res = bpf_map_lookup_elem(&res_map, &zero); if (!my_res) return 1; if (*my_res == 0) /* use bpf_printk() in combination with BPF_NO_GLOBAL_DATA to * force .rodata.str1.1 section that previously caused * problems on old kernels due to libbpf always tried to * create a global data map for it */ bpf_printk("Legacy-case bpf_printk test, pid %d\n", cur_pid); *my_res = 1; return *my_res; } SEC("tp/raw_syscalls/sys_enter") int handle_modern(void *ctx) { int cur_pid; cur_pid = bpf_get_current_pid_tgid() >> 32; if (cur_pid != my_pid_var) return 1; if (res_var == 0) /* we need bpf_printk() to validate libbpf logic around unused * global maps and legacy kernels; see comment in handle_legacy() */ bpf_printk("Modern-case bpf_printk test, pid %d\n", cur_pid); res_var = 1; return res_var; }