12025cf9eSThomas Gleixner // SPDX-License-Identifier: GPL-2.0-only 2a9c909ceSAndy Lutomirski /* 3a9c909ceSAndy Lutomirski * syscall_nt.c - checks syscalls with NT set 4a9c909ceSAndy Lutomirski * Copyright (c) 2014-2015 Andrew Lutomirski 5a9c909ceSAndy Lutomirski * 6a9c909ceSAndy Lutomirski * Some obscure user-space code requires the ability to make system calls 7a9c909ceSAndy Lutomirski * with FLAGS.NT set. Make sure it works. 8a9c909ceSAndy Lutomirski */ 9a9c909ceSAndy Lutomirski 10a9c909ceSAndy Lutomirski #include <stdio.h> 11a9c909ceSAndy Lutomirski #include <unistd.h> 12a318beeaSAndy Lutomirski #include <string.h> 13a318beeaSAndy Lutomirski #include <signal.h> 14a318beeaSAndy Lutomirski #include <err.h> 15a9c909ceSAndy Lutomirski #include <sys/syscall.h> 16a9c909ceSAndy Lutomirski #include <asm/processor-flags.h> 17a9c909ceSAndy Lutomirski 18a9c909ceSAndy Lutomirski #ifdef __x86_64__ 19a9c909ceSAndy Lutomirski # define WIDTH "q" 20a9c909ceSAndy Lutomirski #else 21a9c909ceSAndy Lutomirski # define WIDTH "l" 22a9c909ceSAndy Lutomirski #endif 23a9c909ceSAndy Lutomirski 24a318beeaSAndy Lutomirski static unsigned int nerrs; 25a318beeaSAndy Lutomirski 26a9c909ceSAndy Lutomirski static unsigned long get_eflags(void) 27a9c909ceSAndy Lutomirski { 28a9c909ceSAndy Lutomirski unsigned long eflags; 29a9c909ceSAndy Lutomirski asm volatile ("pushf" WIDTH "\n\tpop" WIDTH " %0" : "=rm" (eflags)); 30a9c909ceSAndy Lutomirski return eflags; 31a9c909ceSAndy Lutomirski } 32a9c909ceSAndy Lutomirski 33a9c909ceSAndy Lutomirski static void set_eflags(unsigned long eflags) 34a9c909ceSAndy Lutomirski { 35a9c909ceSAndy Lutomirski asm volatile ("push" WIDTH " %0\n\tpopf" WIDTH 36a9c909ceSAndy Lutomirski : : "rm" (eflags) : "flags"); 37a9c909ceSAndy Lutomirski } 38a9c909ceSAndy Lutomirski 39a318beeaSAndy Lutomirski static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), 40a318beeaSAndy Lutomirski int flags) 41a318beeaSAndy Lutomirski { 42a318beeaSAndy Lutomirski struct sigaction sa; 43a318beeaSAndy Lutomirski memset(&sa, 0, sizeof(sa)); 44a318beeaSAndy Lutomirski sa.sa_sigaction = handler; 45a318beeaSAndy Lutomirski sa.sa_flags = SA_SIGINFO | flags; 46a318beeaSAndy Lutomirski sigemptyset(&sa.sa_mask); 47a318beeaSAndy Lutomirski if (sigaction(sig, &sa, 0)) 48a318beeaSAndy Lutomirski err(1, "sigaction"); 49a318beeaSAndy Lutomirski } 50a318beeaSAndy Lutomirski 51a318beeaSAndy Lutomirski static void sigtrap(int sig, siginfo_t *si, void *ctx_void) 52a318beeaSAndy Lutomirski { 53a318beeaSAndy Lutomirski } 54a318beeaSAndy Lutomirski 55a318beeaSAndy Lutomirski static void do_it(unsigned long extraflags) 56a318beeaSAndy Lutomirski { 57a318beeaSAndy Lutomirski unsigned long flags; 58a318beeaSAndy Lutomirski 59a318beeaSAndy Lutomirski set_eflags(get_eflags() | extraflags); 60a318beeaSAndy Lutomirski syscall(SYS_getpid); 61a318beeaSAndy Lutomirski flags = get_eflags(); 62a318beeaSAndy Lutomirski if ((flags & extraflags) == extraflags) { 63a318beeaSAndy Lutomirski printf("[OK]\tThe syscall worked and flags are still set\n"); 64a318beeaSAndy Lutomirski } else { 65a318beeaSAndy Lutomirski printf("[FAIL]\tThe syscall worked but flags were cleared (flags = 0x%lx but expected 0x%lx set)\n", 66a318beeaSAndy Lutomirski flags, extraflags); 67a318beeaSAndy Lutomirski nerrs++; 68a318beeaSAndy Lutomirski } 69a318beeaSAndy Lutomirski } 70a318beeaSAndy Lutomirski 71a318beeaSAndy Lutomirski int main(void) 72a9c909ceSAndy Lutomirski { 73a9c909ceSAndy Lutomirski printf("[RUN]\tSet NT and issue a syscall\n"); 74a318beeaSAndy Lutomirski do_it(X86_EFLAGS_NT); 75a318beeaSAndy Lutomirski 76e4ef7de1SAndy Lutomirski printf("[RUN]\tSet AC and issue a syscall\n"); 77e4ef7de1SAndy Lutomirski do_it(X86_EFLAGS_AC); 78e4ef7de1SAndy Lutomirski 79e4ef7de1SAndy Lutomirski printf("[RUN]\tSet NT|AC and issue a syscall\n"); 80e4ef7de1SAndy Lutomirski do_it(X86_EFLAGS_NT | X86_EFLAGS_AC); 81e4ef7de1SAndy Lutomirski 82a318beeaSAndy Lutomirski /* 83a318beeaSAndy Lutomirski * Now try it again with TF set -- TF forces returns via IRET in all 84a318beeaSAndy Lutomirski * cases except non-ptregs-using 64-bit full fast path syscalls. 85a318beeaSAndy Lutomirski */ 86a318beeaSAndy Lutomirski 87a318beeaSAndy Lutomirski sethandler(SIGTRAP, sigtrap, 0); 88a318beeaSAndy Lutomirski 89e4ef7de1SAndy Lutomirski printf("[RUN]\tSet TF and issue a syscall\n"); 90e4ef7de1SAndy Lutomirski do_it(X86_EFLAGS_TF); 91e4ef7de1SAndy Lutomirski 92a318beeaSAndy Lutomirski printf("[RUN]\tSet NT|TF and issue a syscall\n"); 93a318beeaSAndy Lutomirski do_it(X86_EFLAGS_NT | X86_EFLAGS_TF); 94a318beeaSAndy Lutomirski 95e4ef7de1SAndy Lutomirski printf("[RUN]\tSet AC|TF and issue a syscall\n"); 96e4ef7de1SAndy Lutomirski do_it(X86_EFLAGS_AC | X86_EFLAGS_TF); 97e4ef7de1SAndy Lutomirski 98e4ef7de1SAndy Lutomirski printf("[RUN]\tSet NT|AC|TF and issue a syscall\n"); 99e4ef7de1SAndy Lutomirski do_it(X86_EFLAGS_NT | X86_EFLAGS_AC | X86_EFLAGS_TF); 100e4ef7de1SAndy Lutomirski 101a318beeaSAndy Lutomirski return nerrs == 0 ? 0 : 1; 102a9c909ceSAndy Lutomirski } 103