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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2021 Facebook */
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
/* weak and shared between both files */
const volatile int my_tid __weak;
long syscall_id __weak;
int output_val2;
int output_ctx2;
int output_weak2; /* should stay zero */
/* same "subprog" name in all files, but it's ok because they all are static */
static __noinline int subprog(int x)
{
/* but different formula */
return x * 2;
}
/* Global functions can't be void */
int set_output_val2(int x)
{
output_val2 = 2 * x + 2 * subprog(x);
return 2 * x;
}
/* This function can't be verified as global, as it assumes raw_tp/sys_enter
* context and accesses syscall id (second argument). So we mark it as
* __hidden, so that libbpf will mark it as static in the final object file,
* right before verifying it in the kernel.
*
* But we don't mark it as __hidden here, rather at extern site. __hidden is
* "contaminating" visibility, so it will get propagated from either extern or
* actual definition (including from the losing __weak definition).
*/
void set_output_ctx2(__u64 *ctx)
{
output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
}
/* this weak instance should lose, because it will be processed second */
__weak int set_output_weak(int x)
{
output_weak2 = x;
return 2 * x;
}
extern int set_output_val1(int x);
/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
__hidden extern void set_output_ctx1(__u64 *ctx);
SEC("raw_tp/sys_enter")
int BPF_PROG(handler2, struct pt_regs *regs, long id)
{
if (my_tid != (u32)bpf_get_current_pid_tgid() || id != syscall_id)
return 0;
set_output_val1(2000);
set_output_ctx1(ctx); /* ctx definition is hidden in BPF_PROG macro */
/* keep input value the same across both files to avoid dependency on
* handler call order; differentiate by output_weak1 vs output_weak2.
*/
set_output_weak(42);
return 0;
}
char LICENSE[] SEC("license") = "GPL";
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