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

   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}
  97