LXR linux/tools/testing/selftests/x86/syscall

   1/*
   2 * syscall_nt.c - checks syscalls with NT set
   3 * Copyright (c) 2014-2015 Andrew Lutomirski
   4 *
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms and conditions of the GNU General Public License,
   7 * version 2, as published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope it will be useful, but
  10 * WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 * General Public License for more details.
  13 *
  14 * Some obscure user-space code requires the ability to make system calls
  15 * with FLAGS.NT set.  Make sure it works.
  16 */
  17
  18#include <stdio.h>
  19#include <unistd.h>
  20#include <string.h>
  21#include <signal.h>
  22#include <err.h>
  23#include <sys/syscall.h>
  24#include <asm/processor-flags.h>
  25
  26#ifdef __x86_64__
  27# define WIDTH "q"
  28#else
  29# define WIDTH "l"
  30#endif
  31
  32static unsigned int nerrs;
  33
  34static unsigned long get_eflags(void)
  35{
  36        unsigned long eflags;
  37        asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags));
  38        return eflags;
  39}
  40
  41static void set_eflags(unsigned long eflags)
  42{
  43        asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH
  44                      : : "rm" (eflags) : "flags");
  45}
  46
  47static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *),
  48                       int flags)
  49{
  50        struct sigaction sa;
  51        memset(&sa, 0, sizeof(sa));
  52        sa.sa_sigaction = handler;
  53        sa.sa_flags = SA_SIGINFO | flags;
  54        sigemptyset(&sa.sa_mask);
  55        if (sigaction(sig, &sa, 0))
  56                err(1, "sigaction");
  57}
  58
  59static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
  60{
  61}
  62
  63static void do_it(unsigned long extraflags)
  64{
  65        unsigned long flags;
  66
  67        set_eflags(get_eflags() | extraflags);
  68        syscall(SYS_getpid);
  69        flags = get_eflags();
  70        if ((flags & extraflags) == extraflags) {
  71                printf("[OK]\tThe syscall worked and flags are still set\n");
  72        } else {
  73                printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n",
  74                       flags, extraflags);
  75                nerrs++;
  76        }
  77}
  78
  79int main(void)
  80{
  81        printf("[RUN]\tSet NT and issue a syscall\n");
  82        do_it(X86_EFLAGS_NT);
  83
  84        /*
  85         * Now try it again with TF set -- TF forces returns via IRET in all
  86         * cases except non-ptregs-using 64-bit full fast path syscalls.
  87         */
  88
  89        sethandler(SIGTRAP, sigtrap, 0);
  90
  91        printf("[RUN]\tSet NT|TF and issue a syscall\n");
  92        do_it(X86_EFLAGS_NT | X86_EFLAGS_TF);
  93
  94        return nerrs == 0 ? 0 : 1;
  95}
  96