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
 9/* weak and shared between two files */
10const volatile int my_tid __weak;
11long syscall_id __weak;
12
13int output_val1;
14int output_ctx1;
15int output_weak1;
16
17/* same "subprog" name in all files, but it's ok because they all are static */
18static __noinline int subprog(int x)
19{
20	/* but different formula */
21	return x * 1;
22}
23
24/* Global functions can't be void */
25int set_output_val1(int x)
26{
27	output_val1 = x + subprog(x);
28	return x;
29}
30
31/* This function can't be verified as global, as it assumes raw_tp/sys_enter
32 * context and accesses syscall id (second argument). So we mark it as
33 * __hidden, so that libbpf will mark it as static in the final object file,
34 * right before verifying it in the kernel.
35 *
36 * But we don't mark it as __hidden here, rather at extern site. __hidden is
37 * "contaminating" visibility, so it will get propagated from either extern or
38 * actual definition (including from the losing __weak definition).
39 */
40void set_output_ctx1(__u64 *ctx)
41{
42	output_ctx1 = ctx[1]; /* long id, same as in BPF_PROG below */
43}
44
45/* this weak instance should win because it's the first one */
46__weak int set_output_weak(int x)
47{
48	static volatile int whatever;
49
50	/* make sure we use CO-RE relocations in a weak function, this used to
51	 * cause problems for BPF static linker
52	 */
53	whatever = bpf_core_type_size(struct task_struct);
54
55	output_weak1 = x;
56	return x;
57}
58
59extern int set_output_val2(int x);
60
61/* here we'll force set_output_ctx2() to be __hidden in the final obj file */
62__hidden extern void set_output_ctx2(__u64 *ctx);
63
64SEC("?raw_tp/sys_enter")
65int BPF_PROG(handler1, struct pt_regs *regs, long id)
66{
67	static volatile int whatever;
68
69	if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
70		return 0;
71
72	/* make sure we have CO-RE relocations in main program */
73	whatever = bpf_core_type_size(struct task_struct);
74
75	set_output_val2(1000);
76	set_output_ctx2(ctx); /* ctx definition is hidden in BPF_PROG macro */
77
78	/* keep input value the same across both files to avoid dependency on
79	 * handler call order; differentiate by output_weak1 vs output_weak2.
80	 */
81	set_output_weak(42);
82
83	return 0;
84}
85
86char LICENSE[] SEC("license") = "GPL";