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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syscall_nt.c (2414B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * syscall_nt.c - checks syscalls with NT set
      4 * Copyright (c) 2014-2015 Andrew Lutomirski
      5 *
      6 * Some obscure user-space code requires the ability to make system calls
      7 * with FLAGS.NT set.  Make sure it works.
      8 */
      9
     10#include <stdio.h>
     11#include <unistd.h>
     12#include <string.h>
     13#include <signal.h>
     14#include <err.h>
     15#include <sys/syscall.h>
     16
     17#include "helpers.h"
     18
     19static unsigned int nerrs;
     20
     21static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
     22		       int flags)
     23{
     24	struct sigaction sa;
     25	memset(&sa, 0, sizeof(sa));
     26	sa.sa_sigaction = handler;
     27	sa.sa_flags = SA_SIGINFO | flags;
     28	sigemptyset(&sa.sa_mask);
     29	if (sigaction(sig, &sa, 0))
     30		err(1, "sigaction");
     31}
     32
     33static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
     34{
     35}
     36
     37static void do_it(unsigned long extraflags)
     38{
     39	unsigned long flags;
     40
     41	set_eflags(get_eflags() | extraflags);
     42	syscall(SYS_getpid);
     43	flags = get_eflags();
     44	set_eflags(X86_EFLAGS_IF | X86_EFLAGS_FIXED);
     45	if ((flags & extraflags) == extraflags) {
     46		printf("[OK]\tThe syscall worked and flags are still set\n");
     47	} else {
     48		printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
     49		       flags, extraflags);
     50		nerrs++;
     51	}
     52}
     53
     54int main(void)
     55{
     56	printf("[RUN]\tSet NT and issue a syscall\n");
     57	do_it(X86_EFLAGS_NT);
     58
     59	printf("[RUN]\tSet AC and issue a syscall\n");
     60	do_it(X86_EFLAGS_AC);
     61
     62	printf("[RUN]\tSet NT|AC and issue a syscall\n");
     63	do_it(X86_EFLAGS_NT | X86_EFLAGS_AC);
     64
     65	/*
     66	 * Now try it again with TF set -- TF forces returns via IRET in all
     67	 * cases except non-ptregs-using 64-bit full fast path syscalls.
     68	 */
     69
     70	sethandler(SIGTRAP, sigtrap, 0);
     71
     72	printf("[RUN]\tSet TF and issue a syscall\n");
     73	do_it(X86_EFLAGS_TF);
     74
     75	printf("[RUN]\tSet NT|TF and issue a syscall\n");
     76	do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
     77
     78	printf("[RUN]\tSet AC|TF and issue a syscall\n");
     79	do_it(X86_EFLAGS_AC | X86_EFLAGS_TF);
     80
     81	printf("[RUN]\tSet NT|AC|TF and issue a syscall\n");
     82	do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF);
     83
     84	/*
     85	 * Now try DF.  This is evil and it's plausible that we will crash
     86	 * glibc, but glibc would have to do something rather surprising
     87	 * for this to happen.
     88	 */
     89	printf("[RUN]\tSet DF and issue a syscall\n");
     90	do_it(X86_EFLAGS_DF);
     91
     92	printf("[RUN]\tSet TF|DF and issue a syscall\n");
     93	do_it(X86_EFLAGS_TF | X86_EFLAGS_DF);
     94
     95	return nerrs == 0 ? 0 : 1;
     96}