1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */ 3 4 #include <vmlinux.h> 5 #include <bpf/bpf_helpers.h> 6 #include <bpf/bpf_tracing.h> 7 #include <errno.h> 8 9 extern int bpf_kfunc_implicit_arg(int a) __weak __ksym; 10 11 char _license[] SEC("license") = "GPL"; 12 13 /* Shared arg checks; reports arg count and aux, returns 1 on success. */ 14 static __always_inline __u64 15 check_implicit_args(void *ctx, __u64 *arg_cnt, __u64 *aux_arg) 16 { 17 __u64 a = 0, aux = 0, z = 0; 18 __u64 result; 19 __s64 err; 20 21 *arg_cnt = bpf_get_func_arg_cnt(ctx); 22 result = *arg_cnt == 2; 23 24 err = bpf_get_func_arg(ctx, 0, &a); 25 result &= err == 0 && (int)a == 5; 26 27 err = bpf_get_func_arg(ctx, 1, &aux); 28 *aux_arg = aux; 29 result &= err == 0 && aux != 0; 30 31 err = bpf_get_func_arg(ctx, 2, &z); 32 result &= err == -EINVAL; 33 34 return result; 35 } 36 37 __u64 fentry_result; 38 __u64 fentry_arg_cnt; 39 __u64 fentry_aux_arg; 40 41 SEC("fentry/bpf_kfunc_implicit_arg") 42 int BPF_PROG(trace_implicit_arg_fentry) 43 { 44 __u64 ret = 0; 45 __s64 err; 46 47 fentry_result = check_implicit_args(ctx, &fentry_arg_cnt, &fentry_aux_arg); 48 49 err = bpf_get_func_ret(ctx, &ret); 50 fentry_result &= err == -EOPNOTSUPP; 51 52 return 0; 53 } 54 55 __u64 fexit_result; 56 __u64 fexit_arg_cnt; 57 __u64 fexit_aux_arg; 58 59 SEC("fexit/bpf_kfunc_implicit_arg") 60 int BPF_PROG(trace_implicit_arg_fexit) 61 { 62 __u64 ret = 0; 63 __s64 err; 64 65 fexit_result = check_implicit_args(ctx, &fexit_arg_cnt, &fexit_aux_arg); 66 67 err = bpf_get_func_ret(ctx, &ret); 68 fexit_result &= err == 0 && ret == 5; 69 70 return 0; 71 } 72 73 SEC("syscall") 74 int trigger_implicit_arg(void *ctx) 75 { 76 return bpf_kfunc_implicit_arg(5); 77 } 78