tools/testing/selftests/x86/syscall_nt.c

   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
  19 static unsigned int nerrs;
  20
  21 static 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
  33 static void sigtrap(int sig, siginfo_t *si, void *ctx_void)
  34 {
  35 }
  36
  37 static 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
  54 int 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 }