cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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linked_funcs2.c (2394B)

      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 both files */
     10const volatile int my_tid __weak;
     11long syscall_id __weak;
     12
     13int output_val2;
     14int output_ctx2;
     15int output_weak2; /* should stay zero */
     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 * 2;
     22}
     23
     24/* Global functions can't be void */
     25int set_output_val2(int x)
     26{
     27	output_val2 = 2 * x + 2 * subprog(x);
     28	return 2 * 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_ctx2(__u64 *ctx)
     41{
     42	output_ctx2 = ctx[1]; /* long id, same as in BPF_PROG below */
     43}
     44
     45/* this weak instance should lose, because it will be processed second */
     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 = 2 * bpf_core_type_size(struct task_struct);
     54
     55	output_weak2 = x;
     56	return 2 * x;
     57}
     58
     59extern int set_output_val1(int x);
     60
     61/* here we'll force set_output_ctx1() to be __hidden in the final obj file */
     62__hidden extern void set_output_ctx1(__u64 *ctx);
     63
     64SEC("?raw_tp/sys_enter")
     65int BPF_PROG(handler2, 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_val1(2000);
     76	set_output_ctx1(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";