From: Denys Vlasenko <dvlasenk@redhat.com>
To: hpa@zytor.com, torvalds@linux-foundation.org, luto@kernel.org,
mingo@kernel.org, bp@alien8.de, linux-kernel@vger.kernel.org,
linux@dominikbrodowski.net, brgerst@gmail.com,
peterz@infradead.org, tglx@linutronix.de, jpoimboe@redhat.com,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/pti] x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro
Date: Mon, 12 Feb 2018 14:29:27 +0100 [thread overview]
Message-ID: <22559e63-5b78-21a7-27cd-a985957d5879@redhat.com> (raw)
In-Reply-To: <tip-7b7b09f110f06f3c006e9b3f4590f7d9ba91345b@git.kernel.org>
On 02/12/2018 11:17 AM, tip-bot for Dominik Brodowski wrote:
> Commit-ID: 7b7b09f110f06f3c006e9b3f4590f7d9ba91345b
> Gitweb: https://git.kernel.org/tip/7b7b09f110f06f3c006e9b3f4590f7d9ba91345b
> Author: Dominik Brodowski <linux@dominikbrodowski.net>
> AuthorDate: Sun, 11 Feb 2018 11:49:45 +0100
> Committer: Ingo Molnar <mingo@kernel.org>
> CommitDate: Mon, 12 Feb 2018 08:06:36 +0100
>
> x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro
>
> Those instances where ALLOC_PT_GPREGS_ON_STACK is called just before
> SAVE_AND_CLEAR_REGS can trivially be replaced by PUSH_AND_CLEAN_REGS.
> This macro uses PUSH instead of MOV and should therefore be faster, at
> least on newer CPUs.
>
> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Brian Gerst <brgerst@gmail.com>
> Cc: Denys Vlasenko <dvlasenk@redhat.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: dan.j.williams@intel.com
> Link: http://lkml.kernel.org/r/20180211104949.12992-5-linux@dominikbrodowski.net
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> ---
> arch/x86/entry/calling.h | 36 ++++++++++++++++++++++++++++++++++++
> arch/x86/entry/entry_64.S | 6 ++----
> 2 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
> index a05cbb8..57b1b87 100644
> --- a/arch/x86/entry/calling.h
> +++ b/arch/x86/entry/calling.h
> @@ -137,6 +137,42 @@ For 32-bit we have the following conventions - kernel is built with
> UNWIND_HINT_REGS offset=\offset
> .endm
>
> + .macro PUSH_AND_CLEAR_REGS
> + /*
> + * Push 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:
> + */
> + pushq %rdi /* pt_regs->di */
> + pushq %rsi /* pt_regs->si */
> + pushq %rdx /* pt_regs->dx */
> + pushq %rcx /* pt_regs->cx */
> + pushq %rax /* pt_regs->ax */
> + pushq %r8 /* pt_regs->r8 */
> + xorq %r8, %r8 /* nospec r8 */
xorq's are slower than xorl's on Silvermont/Knights Landing.
I propose using xorl instead.
> + 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*/
next prev parent reply other threads:[~2018-02-12 13:29 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-11 10:49 [PATCH v3 0/7] x86/entry: simplify and unify SAVE/POP_REGS Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 1/7] x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions Dominik Brodowski
2018-02-12 10:15 ` [tip:x86/pti] x86/entry/64: Merge " tip-bot for Dominik Brodowski
2018-02-13 9:00 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 2/7] x86/entry: merge POP_C_REGS and POP_EXTRA_REGS Dominik Brodowski
2018-02-12 10:16 ` [tip:x86/pti] x86/entry/64: Merge the POP_C_REGS and POP_EXTRA_REGS macros into a single POP_REGS macro tip-bot for Dominik Brodowski
2018-02-13 9:01 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 3/7] x86/entry: interleave XOR register clearing with PUSH instructions Dominik Brodowski
2018-02-12 10:16 ` [tip:x86/pti] x86/entry/64: Interleave " tip-bot for Dominik Brodowski
2018-02-13 9:01 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 4/7] x86/entry: introduce PUSH_AND_CLEAN_REGS Dominik Brodowski
2018-02-12 10:17 ` [tip:x86/pti] x86/entry/64: Introduce the PUSH_AND_CLEAN_REGS macro tip-bot for Dominik Brodowski
2018-02-12 13:29 ` Denys Vlasenko [this message]
2018-02-12 13:36 ` David Laight
2018-02-12 13:43 ` Denys Vlasenko
2018-02-12 16:51 ` Linus Torvalds
2018-02-13 9:01 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 5/7] x86/entry: use PUSH_AND_CLEAN_REGS in more cases Dominik Brodowski
2018-02-12 10:17 ` [tip:x86/pti] x86/entry/64: Use " tip-bot for Dominik Brodowski
2018-02-13 9:02 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 6/7] x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS Dominik Brodowski
2018-02-12 10:18 ` [tip:x86/pti] x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros tip-bot for Dominik Brodowski
2018-02-13 9:02 ` tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 7/7] x86/entry: indent PUSH_AND_CLEAR_REGS and POP_REGS properly Dominik Brodowski
2018-02-12 10:18 ` [tip:x86/pti] x86/entry/64: Indent " tip-bot for Dominik Brodowski
2018-02-12 20:13 ` [PATCH] x86/entry/64: Remove unused icebp macro Borislav Petkov
2018-02-13 7:36 ` Ingo Molnar
2018-02-13 9:04 ` [tip:x86/pti] x86/entry/64: Remove the unused 'icebp' macro tip-bot for Borislav Petkov
2018-02-13 9:03 ` [tip:x86/pti] x86/entry/64: Indent PUSH_AND_CLEAR_REGS and POP_REGS properly tip-bot for Dominik Brodowski
2018-02-11 10:49 ` [PATCH v3 8/7] TESTING_ONLY x86/entry: reduce static footprint of idtentry Dominik Brodowski
2018-02-12 9:37 ` Ingo Molnar
2018-02-12 19:17 ` Linus Torvalds
2018-02-13 12:41 ` Ingo Molnar
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