From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754128AbbDPQRG (ORCPT ); Thu, 16 Apr 2015 12:17:06 -0400 Received: from terminus.zytor.com ([198.137.202.10]:46412 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754024AbbDPQQx (ORCPT ); Thu, 16 Apr 2015 12:16:53 -0400 Date: Thu, 16 Apr 2015 09:16:08 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: shuah.kh@samsung.com, mingo@kernel.org, linux-kernel@vger.kernel.org, oleg@redhat.com, hpa@zytor.com, vda.linux@googlemail.com, tglx@linutronix.de, bp@alien8.de, luto@kernel.org Reply-To: mingo@kernel.org, linux-kernel@vger.kernel.org, shuah.kh@samsung.com, oleg@redhat.com, hpa@zytor.com, vda.linux@googlemail.com, bp@alien8.de, luto@kernel.org, tglx@linutronix.de In-Reply-To: <20e68021155f6ab5c60590dcad81d37c68ea2c4f.1429139075.git.luto@kernel.org> References: <20e68021155f6ab5c60590dcad81d37c68ea2c4f.1429139075.git.luto@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86, selftests: Add single_step_syscall test Git-Commit-ID: 0a15584d72760a3b83d97af85d37ffaa2c42068d X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 0a15584d72760a3b83d97af85d37ffaa2c42068d Gitweb: http://git.kernel.org/tip/0a15584d72760a3b83d97af85d37ffaa2c42068d Author: Andy Lutomirski AuthorDate: Wed, 15 Apr 2015 16:10:07 -0700 Committer: Ingo Molnar CommitDate: Thu, 16 Apr 2015 12:41:49 +0200 x86, selftests: Add single_step_syscall test This is a very simple test that makes system calls with TF set. This test currently fails when running the 32-bit build on a 64-bit kernel on an Intel CPU. This bug will be fixed by the next commit. Signed-off-by: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: Oleg Nesterov Cc: Shuah Khan Link: http://lkml.kernel.org/r/20e68021155f6ab5c60590dcad81d37c68ea2c4f.1429139075.git.luto@kernel.org Signed-off-by: Ingo Molnar --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/run_x86_tests.sh | 2 + tools/testing/selftests/x86/single_step_syscall.c | 181 ++++++++++++++++++++++ 3 files changed, 184 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index f0a7918..ddf6356 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -1,6 +1,6 @@ .PHONY: all all_32 all_64 check_build32 clean run_tests -TARGETS_C_BOTHBITS := sigreturn +TARGETS_C_BOTHBITS := sigreturn single_step_syscall BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32) BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64) diff --git a/tools/testing/selftests/x86/run_x86_tests.sh b/tools/testing/selftests/x86/run_x86_tests.sh index 3d3ec65..3fc19b3 100644 --- a/tools/testing/selftests/x86/run_x86_tests.sh +++ b/tools/testing/selftests/x86/run_x86_tests.sh @@ -3,9 +3,11 @@ # This is deliberately minimal. IMO kselftests should provide a standard # script here. ./sigreturn_32 || exit 1 +./single_step_syscall_32 || exit 1 if [[ "$uname -p" -eq "x86_64" ]]; then ./sigreturn_64 || exit 1 + ./single_step_syscall_64 || exit 1 fi exit 0 diff --git a/tools/testing/selftests/x86/single_step_syscall.c b/tools/testing/selftests/x86/single_step_syscall.c new file mode 100644 index 0000000..50c2635 --- /dev/null +++ b/tools/testing/selftests/x86/single_step_syscall.c @@ -0,0 +1,181 @@ +/* + * single_step_syscall.c - single-steps various x86 syscalls + * 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. + * + * This is a very simple series of tests that makes system calls with + * the TF flag set. This exercises some nasty kernel code in the + * SYSENTER case: SYSENTER does not clear TF, so SYSENTER with TF set + * immediately issues #DB from CPL 0. This requires special handling in + * the kernel. + */ + +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +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 volatile sig_atomic_t sig_traps; + +#ifdef __x86_64__ +# define REG_IP REG_RIP +# define WIDTH "q" +#else +# define REG_IP REG_EIP +# define WIDTH "l" +#endif + +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"); +} + +#define X86_EFLAGS_TF (1UL << 8) + +static void sigtrap(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t*)ctx_void; + + if (get_eflags() & X86_EFLAGS_TF) { + set_eflags(get_eflags() & ~X86_EFLAGS_TF); + printf("[WARN]\tSIGTRAP handler had TF set\n"); + _exit(1); + } + + sig_traps++; + + if (sig_traps == 10000 || sig_traps == 10001) { + printf("[WARN]\tHit %d SIGTRAPs with si_addr 0x%lx, ip 0x%lx\n", + (int)sig_traps, + (unsigned long)info->si_addr, + (unsigned long)ctx->uc_mcontext.gregs[REG_IP]); + } +} + +static void check_result(void) +{ + unsigned long new_eflags = get_eflags(); + set_eflags(new_eflags & ~X86_EFLAGS_TF); + + if (!sig_traps) { + printf("[FAIL]\tNo SIGTRAP\n"); + exit(1); + } + + if (!(new_eflags & X86_EFLAGS_TF)) { + printf("[FAIL]\tTF was cleared\n"); + exit(1); + } + + printf("[OK]\tSurvived with TF set and %d traps\n", (int)sig_traps); + sig_traps = 0; +} + +int main() +{ + int tmp; + + sethandler(SIGTRAP, sigtrap, 0); + + printf("[RUN]\tSet TF and check nop\n"); + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ("nop"); + check_result(); + +#ifdef __x86_64__ + printf("[RUN]\tSet TF and check syscall-less opportunistic sysret\n"); + set_eflags(get_eflags() | X86_EFLAGS_TF); + extern unsigned char post_nop[]; + asm volatile ("pushf" WIDTH "\n\t" + "pop" WIDTH " %%r11\n\t" + "nop\n\t" + "post_nop:" + : : "c" (post_nop) : "r11"); + check_result(); +#endif + + printf("[RUN]\tSet TF and check int80\n"); + set_eflags(get_eflags() | X86_EFLAGS_TF); + asm volatile ("int $0x80" : "=a" (tmp) : "a" (SYS_getpid)); + check_result(); + + /* + * This test is particularly interesting if fast syscalls use + * SYSENTER: it triggers a nasty design flaw in SYSENTER. + * Specifically, SYSENTER does not clear TF, so either SYSENTER + * or the next instruction traps at CPL0. (Of course, Intel + * mostly forgot to document exactly what happens here.) So we + * get a CPL0 fault with usergs (on 64-bit kernels) and possibly + * no stack. The only sane way the kernel can possibly handle + * it is to clear TF on return from the #DB handler, but this + * happens way too early to set TF in the saved pt_regs, so the + * kernel has to do something clever to avoid losing track of + * the TF bit. + * + * Needless to say, we've had bugs in this area. + */ + syscall(SYS_getpid); /* Force symbol binding without TF set. */ + printf("[RUN]\tSet TF and check a fast syscall\n"); + set_eflags(get_eflags() | X86_EFLAGS_TF); + syscall(SYS_getpid); + check_result(); + + /* Now make sure that another fast syscall doesn't set TF again. */ + printf("[RUN]\tFast syscall with TF cleared\n"); + fflush(stdout); /* Force a syscall */ + if (get_eflags() & X86_EFLAGS_TF) { + printf("[FAIL]\tTF is now set\n"); + exit(1); + } + if (sig_traps) { + printf("[FAIL]\tGot SIGTRAP\n"); + exit(1); + } + printf("[OK]\tNothing unexpected happened\n"); + + return 0; +}