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#include <bpf/bpf_core_read.h>
8#include "bpf_misc.h"
9
10/* weak and shared between both files */
11const volatile int my_tid __weak;
12long syscall_id __weak;
13
14int output_val2;
15int output_ctx2;
16int output_weak2; /* should stay zero */
17
18/* same "subprog" name in all files, but it's ok because they all are static */
19static __noinline int subprog(int x)
20{
21	/* but different formula */
22	return x * 2;
23}
24
25/* Global functions can't be void */
26int set_output_val2(int x)
27{
28	output_val2 = 2 * x + 2 * subprog(x);
29	return 2 * x;
30}
31
32/* This function can't be verified as global, as it assumes raw_tp/sys_enter
33 * context and accesses syscall id (second argument). So we mark it as
34 * __hidden, so that libbpf will mark it as static in the final object file,
35 * right before verifying it in the kernel.
36 *
37 * But we don't mark it as __hidden here, rather at extern site. __hidden is
38 * "contaminating" visibility, so it will get propagated from either extern or
39 * actual definition (including from the losing __weak definition).
40 */
41void set_output_ctx2(__u64 *ctx)
42{
43	output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
44}
45
46/* this weak instance should lose, because it will be processed second */
47__weak int set_output_weak(int x)
48{
49	static volatile int whatever;
50
51	/* make sure we use CO-RE relocations in a weak function, this used to
52	 * cause problems for BPF static linker
53	 */
54	whatever = 2 * bpf_core_type_size(struct task_struct);
55	__sink(whatever);
56
57	output_weak2 = x;
58	return 2 * x;
59}
60
61extern int set_output_val1(int x);
62
63/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
64__hidden extern void set_output_ctx1(__u64 *ctx);
65
66SEC("?raw_tp/sys_enter")
67int BPF_PROG(handler2, struct pt_regs *regs, long id)
68{
69	static volatile int whatever;
70
71	if (my_tid != (s32)bpf_get_current_pid_tgid() || id != syscall_id)
72		return 0;
73
74	/* make sure we have CO-RE relocations in main program */
75	whatever = bpf_core_type_size(struct task_struct);
76	__sink(whatever);
77
78	set_output_val1(2000);
79	set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */
80
81	/* keep input value the same across both files to avoid dependency on
82	 * handler call order; differentiate by output_weak1 vs output_weak2.
83	 */
84	set_output_weak(42);
85
86	return 0;
87}
88
89char LICENSE[] SEC("license") = "GPL";
90