1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* Copyright (c) 2021 Hengqi Chen */ 3 4 #include "vmlinux.h" 5 #include <bpf/bpf_helpers.h> 6 #include <bpf/bpf_tracing.h> 7 8 const volatile pid_t my_pid = 0; 9 int value = 0; 10 11 SEC("raw_tp/sys_enter") 12 int tailcall_1(void *ctx) 13 { 14 value = 42; 15 return 0; 16 } 17 18 struct { 19 __uint(type, BPF_MAP_TYPE_PROG_ARRAY); 20 __uint(max_entries, 2); 21 __uint(key_size, sizeof(__u32)); 22 __array(values, int (void *)); 23 } prog_array_init SEC(".maps") = { 24 .values = { 25 [1] = (void *)&tailcall_1, 26 }, 27 }; 28 29 SEC("raw_tp/sys_enter") 30 int entry(void *ctx) 31 { 32 pid_t pid = bpf_get_current_pid_tgid() >> 32; 33 34 if (pid != my_pid) 35 return 0; 36 37 bpf_tail_call(ctx, &prog_array_init, 1); 38 return 0; 39 } 40