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 sigtrap(int sig,siginfo_t * si,void * ctx_void)21static void sigtrap(int sig, siginfo_t *si, void *ctx_void) 22 { 23 } 24 do_it(unsigned long extraflags)25static void do_it(unsigned long extraflags) 26 { 27 unsigned long flags; 28 29 set_eflags(get_eflags() | extraflags); 30 syscall(SYS_getpid); 31 flags = get_eflags(); 32 set_eflags(X86_EFLAGS_IF | X86_EFLAGS_FIXED); 33 if ((flags & extraflags) == extraflags) { 34 printf("[OK]\tThe syscall worked and flags are still set\n"); 35 } else { 36 printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n", 37 flags, extraflags); 38 nerrs++; 39 } 40 } 41 main(void)42int main(void) 43 { 44 printf("[RUN]\tSet NT and issue a syscall\n"); 45 do_it(X86_EFLAGS_NT); 46 47 printf("[RUN]\tSet AC and issue a syscall\n"); 48 do_it(X86_EFLAGS_AC); 49 50 printf("[RUN]\tSet NT|AC and issue a syscall\n"); 51 do_it(X86_EFLAGS_NT | X86_EFLAGS_AC); 52 53 /* 54 * Now try it again with TF set -- TF forces returns via IRET in all 55 * cases except non-ptregs-using 64-bit full fast path syscalls. 56 */ 57 58 sethandler(SIGTRAP, sigtrap, 0); 59 60 printf("[RUN]\tSet TF and issue a syscall\n"); 61 do_it(X86_EFLAGS_TF); 62 63 printf("[RUN]\tSet NT|TF and issue a syscall\n"); 64 do_it(X86_EFLAGS_NT | X86_EFLAGS_TF); 65 66 printf("[RUN]\tSet AC|TF and issue a syscall\n"); 67 do_it(X86_EFLAGS_AC | X86_EFLAGS_TF); 68 69 printf("[RUN]\tSet NT|AC|TF and issue a syscall\n"); 70 do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF); 71 72 /* 73 * Now try DF. This is evil and it's plausible that we will crash 74 * glibc, but glibc would have to do something rather surprising 75 * for this to happen. 76 */ 77 printf("[RUN]\tSet DF and issue a syscall\n"); 78 do_it(X86_EFLAGS_DF); 79 80 printf("[RUN]\tSet TF|DF and issue a syscall\n"); 81 do_it(X86_EFLAGS_TF | X86_EFLAGS_DF); 82 83 return nerrs == 0 ? 0 : 1; 84 } 85