| /* |
| * syscall_nt.c - checks syscalls with NT set |
| * Copyright (c) 2014-2015 Andrew Lutomirski |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms and conditions of the GNU General Public License, |
| * version 2, as published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| * |
| * Some obscure user-space code requires the ability to make system calls |
| * with FLAGS.NT set. Make sure it works. |
| */ |
| |
| #include <stdio.h> |
| #include <unistd.h> |
| #include <string.h> |
| #include <signal.h> |
| #include <err.h> |
| #include <sys/syscall.h> |
| #include <asm/processor-flags.h> |
| |
| #ifdef __x86_64__ |
| # define WIDTH "q" |
| #else |
| # define WIDTH "l" |
| #endif |
| |
| static unsigned int nerrs; |
| |
| static unsigned long get_eflags(void) |
| { |
| unsigned long eflags; |
| asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags)); |
| return eflags; |
| } |
| |
| static void set_eflags(unsigned long eflags) |
| { |
| asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH |
| : : "rm" (eflags) : "flags"); |
| } |
| |
| static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), |
| int flags) |
| { |
| struct sigaction sa; |
| memset(&sa, 0, sizeof(sa)); |
| sa.sa_sigaction = handler; |
| sa.sa_flags = SA_SIGINFO | flags; |
| sigemptyset(&sa.sa_mask); |
| if (sigaction(sig, &sa, 0)) |
| err(1, "sigaction"); |
| } |
| |
| static void sigtrap(int sig, siginfo_t *si, void *ctx_void) |
| { |
| } |
| |
| static void do_it(unsigned long extraflags) |
| { |
| unsigned long flags; |
| |
| set_eflags(get_eflags() | extraflags); |
| syscall(SYS_getpid); |
| flags = get_eflags(); |
| if ((flags & extraflags) == extraflags) { |
| printf("[OK]\tThe syscall worked and flags are still set\n"); |
| } else { |
| printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n", |
| flags, extraflags); |
| nerrs++; |
| } |
| } |
| |
| int main(void) |
| { |
| printf("[RUN]\tSet NT and issue a syscall\n"); |
| do_it(X86_EFLAGS_NT); |
| |
| /* |
| * Now try it again with TF set -- TF forces returns via IRET in all |
| * cases except non-ptregs-using 64-bit full fast path syscalls. |
| */ |
| |
| sethandler(SIGTRAP, sigtrap, 0); |
| |
| printf("[RUN]\tSet NT|TF and issue a syscall\n"); |
| do_it(X86_EFLAGS_NT | X86_EFLAGS_TF); |
| |
| return nerrs == 0 ? 0 : 1; |
| } |