1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2021 Facebook */
 3
 4#include "vmlinux.h"
 5#include <bpf/bpf_helpers.h>
 6#include <bpf/bpf_tracing.h>
 7
 8/* weak and shared between both files */
 9const volatile int my_tid __weak;
10long syscall_id __weak;
11
12int output_val2;
13int output_ctx2;
14int output_weak2; /* should stay zero */
15
16/* same "subprog" name in all files, but it's ok because they all are static */
17static __noinline int subprog(int x)
18{
19	/* but different formula */
20	return x * 2;
21}
22
23/* Global functions can't be void */
24int set_output_val2(int x)
25{
26	output_val2 = 2 * x + 2 * subprog(x);
27	return 2 * x;
28}
29
30/* This function can't be verified as global, as it assumes raw_tp/sys_enter
31 * context and accesses syscall id (second argument). So we mark it as
32 * __hidden, so that libbpf will mark it as static in the final object file,
33 * right before verifying it in the kernel.
34 *
35 * But we don't mark it as __hidden here, rather at extern site. __hidden is
36 * "contaminating" visibility, so it will get propagated from either extern or
37 * actual definition (including from the losing __weak definition).
38 */
39void set_output_ctx2(__u64 *ctx)
40{
41	output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
42}
43
44/* this weak instance should lose, because it will be processed second */
45__weak int set_output_weak(int x)
46{
47	output_weak2 = x;
48	return 2 * x;
49}
50
51extern int set_output_val1(int x);
52
53/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
54__hidden extern void set_output_ctx1(__u64 *ctx);
55
56SEC("raw_tp/sys_enter")
57int BPF_PROG(handler2, struct pt_regs *regs, long id)
58{
59	if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
60		return 0;
61
62	set_output_val1(2000);
63	set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */
64
65	/* keep input value the same across both files to avoid dependency on
66	 * handler call order; differentiate by output_weak1 vs output_weak2.
67	 */
68	set_output_weak(42);
69
70	return 0;
71}
72
73char LICENSE[] SEC("license") = "GPL";