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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * syscall_nt.c - checks syscalls with NT set4 * Copyright (c) 2014-2015 Andrew Lutomirski5 *6 * Some obscure user-space code requires the ability to make system calls7 * 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 all67 * 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 crash86 * glibc, but glibc would have to do something rather surprising87 * 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