From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933507AbeBLKRm (ORCPT ); Mon, 12 Feb 2018 05:17:42 -0500 Received: from [198.137.202.136] ([198.137.202.136]:37081 "EHLO terminus.zytor.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S932756AbeBLKRj (ORCPT ); Mon, 12 Feb 2018 05:17:39 -0500 Date: Mon, 12 Feb 2018 02:16:57 -0800 From: tip-bot for Dominik Brodowski Message-ID: Cc: bp@alien8.de, tglx@linutronix.de, hpa@zytor.com, torvalds@linux-foundation.org, jpoimboe@redhat.com, luto@kernel.org, dvlasenk@redhat.com, brgerst@gmail.com, linux@dominikbrodowski.net, mingo@kernel.org, linux-kernel@vger.kernel.org, peterz@infradead.org Reply-To: luto@kernel.org, dvlasenk@redhat.com, mingo@kernel.org, brgerst@gmail.com, linux@dominikbrodowski.net, linux-kernel@vger.kernel.org, peterz@infradead.org, bp@alien8.de, tglx@linutronix.de, hpa@zytor.com, torvalds@linux-foundation.org, jpoimboe@redhat.com In-Reply-To: <20180211104949.12992-4-linux@dominikbrodowski.net> References: <20180211104949.12992-4-linux@dominikbrodowski.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/pti] x86/entry/64: Interleave XOR register clearing with PUSH instructions Git-Commit-ID: e922c091d34db9dec1eeb6e7b923043ae4d366e3 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: e922c091d34db9dec1eeb6e7b923043ae4d366e3 Gitweb: https://git.kernel.org/tip/e922c091d34db9dec1eeb6e7b923043ae4d366e3 Author: Dominik Brodowski AuthorDate: Sun, 11 Feb 2018 11:49:44 +0100 Committer: Ingo Molnar CommitDate: Mon, 12 Feb 2018 08:06:35 +0100 x86/entry/64: Interleave XOR register clearing with PUSH instructions Same as is done for syscalls, interleave XOR with PUSH instructions for exceptions/interrupts, in order to minimize the cost of the additional instructions required for register clearing. Signed-off-by: Dominik Brodowski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dan.j.williams@intel.com Link: http://lkml.kernel.org/r/20180211104949.12992-4-linux@dominikbrodowski.net Signed-off-by: Ingo Molnar --- arch/x86/entry/calling.h | 40 +++++++++++++++++++--------------------- arch/x86/entry/entry_64.S | 30 +++++++++++++++++++++--------- 2 files changed, 40 insertions(+), 30 deletions(-) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 3bda317..a05cbb8 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -101,44 +101,42 @@ For 32-bit we have the following conventions - kernel is built with addq $-(15*8), %rsp .endm - .macro SAVE_REGS offset=0 + .macro SAVE_AND_CLEAR_REGS offset=0 + /* + * Save registers and sanitize registers of values that a + * speculation attack might otherwise want to exploit. The + * lower registers are likely clobbered well before they + * could be put to use in a speculative execution gadget. + * Interleave XOR with PUSH for better uop scheduling: + */ movq %rdi, 14*8+\offset(%rsp) movq %rsi, 13*8+\offset(%rsp) movq %rdx, 12*8+\offset(%rsp) movq %rcx, 11*8+\offset(%rsp) movq %rax, 10*8+\offset(%rsp) movq %r8, 9*8+\offset(%rsp) + xorq %r8, %r8 /* nospec r8 */ movq %r9, 8*8+\offset(%rsp) + xorq %r9, %r9 /* nospec r9 */ movq %r10, 7*8+\offset(%rsp) + xorq %r10, %r10 /* nospec r10 */ movq %r11, 6*8+\offset(%rsp) + xorq %r11, %r11 /* nospec r11 */ movq %rbx, 5*8+\offset(%rsp) + xorl %ebx, %ebx /* nospec rbx */ movq %rbp, 4*8+\offset(%rsp) + xorl %ebp, %ebp /* nospec rbp */ movq %r12, 3*8+\offset(%rsp) + xorq %r12, %r12 /* nospec r12 */ movq %r13, 2*8+\offset(%rsp) + xorq %r13, %r13 /* nospec r13 */ movq %r14, 1*8+\offset(%rsp) + xorq %r14, %r14 /* nospec r14 */ movq %r15, 0*8+\offset(%rsp) + xorq %r15, %r15 /* nospec r15 */ UNWIND_HINT_REGS offset=\offset .endm - /* - * Sanitize registers of values that a speculation attack - * might otherwise want to exploit. The lower registers are - * likely clobbered well before they could be put to use in - * a speculative execution gadget: - */ - .macro CLEAR_REGS_NOSPEC - xorl %ebp, %ebp - xorl %ebx, %ebx - xorq %r8, %r8 - xorq %r9, %r9 - xorq %r10, %r10 - xorq %r11, %r11 - xorq %r12, %r12 - xorq %r13, %r13 - xorq %r14, %r14 - xorq %r15, %r15 - .endm - .macro POP_REGS pop_rdi=1 skip_r11rcx=0 popq %r15 popq %r14 @@ -177,7 +175,7 @@ For 32-bit we have the following conventions - kernel is built with * is just setting the LSB, which makes it an invalid stack address and is also * a signal to the unwinder that it's a pt_regs pointer in disguise. * - * NOTE: This macro must be used *after* SAVE_REGS because it corrupts + * NOTE: This macro must be used *after* SAVE_AND_CLEAR_REGS because it corrupts * the original rbp. */ .macro ENCODE_FRAME_POINTER ptregs_offset=0 diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 7351c91..07692b4 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -565,8 +565,7 @@ END(irq_entries_start) 1: ALLOC_PT_GPREGS_ON_STACK - SAVE_REGS - CLEAR_REGS_NOSPEC + SAVE_AND_CLEAR_REGS ENCODE_FRAME_POINTER testb $3, CS(%rsp) @@ -1114,8 +1113,7 @@ ENTRY(xen_failsafe_callback) UNWIND_HINT_IRET_REGS pushq $-1 /* orig_ax = -1 => not a system call */ ALLOC_PT_GPREGS_ON_STACK - SAVE_REGS - CLEAR_REGS_NOSPEC + SAVE_AND_CLEAR_REGS ENCODE_FRAME_POINTER jmp error_exit END(xen_failsafe_callback) @@ -1159,8 +1157,7 @@ idtentry machine_check do_mce has_error_code=0 paranoid=1 ENTRY(paranoid_entry) UNWIND_HINT_FUNC cld - SAVE_REGS 8 - CLEAR_REGS_NOSPEC + SAVE_AND_CLEAR_REGS 8 ENCODE_FRAME_POINTER 8 movl $1, %ebx movl $MSR_GS_BASE, %ecx @@ -1211,8 +1208,7 @@ END(paranoid_exit) ENTRY(error_entry) UNWIND_HINT_FUNC cld - SAVE_REGS 8 - CLEAR_REGS_NOSPEC + SAVE_AND_CLEAR_REGS 8 ENCODE_FRAME_POINTER 8 testb $3, CS+8(%rsp) jz .Lerror_kernelspace @@ -1399,18 +1395,34 @@ ENTRY(nmi) pushq (%rdx) /* pt_regs->dx */ pushq %rcx /* pt_regs->cx */ pushq %rax /* pt_regs->ax */ + /* + * Sanitize registers of values that a speculation attack + * might otherwise want to exploit. The lower registers are + * likely clobbered well before they could be put to use in + * a speculative execution gadget. Interleave XOR with PUSH + * for better uop scheduling: + */ pushq %r8 /* pt_regs->r8 */ + xorq %r8, %r8 /* nospec r8 */ pushq %r9 /* pt_regs->r9 */ + xorq %r9, %r9 /* nospec r9 */ pushq %r10 /* pt_regs->r10 */ + xorq %r10, %r10 /* nospec r10 */ pushq %r11 /* pt_regs->r11 */ + xorq %r11, %r11 /* nospec r11*/ pushq %rbx /* pt_regs->rbx */ + xorl %ebx, %ebx /* nospec rbx*/ pushq %rbp /* pt_regs->rbp */ + xorl %ebp, %ebp /* nospec rbp*/ pushq %r12 /* pt_regs->r12 */ + xorq %r12, %r12 /* nospec r12*/ pushq %r13 /* pt_regs->r13 */ + xorq %r13, %r13 /* nospec r13*/ pushq %r14 /* pt_regs->r14 */ + xorq %r14, %r14 /* nospec r14*/ pushq %r15 /* pt_regs->r15 */ + xorq %r15, %r15 /* nospec r15*/ UNWIND_HINT_REGS - CLEAR_REGS_NOSPEC ENCODE_FRAME_POINTER /*