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
check_implicit_args(void * ctx,__u64 * arg_cnt,__u64 * aux_arg)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")
BPF_PROG(trace_implicit_arg_fentry)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")
BPF_PROG(trace_implicit_arg_fexit)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")
trigger_implicit_arg(void * ctx)74 int trigger_implicit_arg(void *ctx)
75 {
76 return bpf_kfunc_implicit_arg(5);
77 }
78