From: Borislav Petkov <bp@alien8.de>
To: dwmw@amazon.co.uk
Cc: tim.c.chen@linux.intel.com, pjt@google.com, jikos@kernel.org,
gregkh@linux-foundation.org, dave.hansen@intel.com,
mingo@kernel.org, riel@redhat.com, luto@amacapital.net,
torvalds@linux-foundation.org, ak@linux.intel.com,
keescook@google.com, jpoimboe@redhat.com, peterz@infradead.org,
tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/pti] x86/retpoline: Fill return stack buffer on vmexit
Date: Sun, 14 Jan 2018 16:35:48 +0100 [thread overview]
Message-ID: <20180114153547.5lq6xermghzbp43t@pd.tnic> (raw)
In-Reply-To: <tip-117cc7a908c83697b0b737d15ae1eb5943afe35b@git.kernel.org>
On Fri, Jan 12, 2018 at 03:37:49AM -0800, tip-bot for David Woodhouse wrote:
> Commit-ID: 117cc7a908c83697b0b737d15ae1eb5943afe35b
> Gitweb: https://git.kernel.org/tip/117cc7a908c83697b0b737d15ae1eb5943afe35b
> Author: David Woodhouse <dwmw@amazon.co.uk>
> AuthorDate: Fri, 12 Jan 2018 11:11:27 +0000
> Committer: Thomas Gleixner <tglx@linutronix.de>
> CommitDate: Fri, 12 Jan 2018 12:33:37 +0100
>
> x86/retpoline: Fill return stack buffer on vmexit
...
> +/*
> + * Google experimented with loop-unrolling and this turned out to be
> + * the optimal version — two calls, each with their own speculation
> + * trap should their return address end up getting used, in a loop.
> + */
> +#define __FILL_RETURN_BUFFER(reg, nr, sp) \
> + mov $(nr/2), reg; \
> +771: \
> + call 772f; \
> +773: /* speculation trap */ \
> + pause; \
> + jmp 773b; \
> +772: \
> + call 774f; \
> +775: /* speculation trap */ \
> + pause; \
> + jmp 775b; \
> +774: \
> + dec reg; \
> + jnz 771b; \
> + add $(BITS_PER_LONG/8) * nr, sp;
> +
Btw, just a minor nit: one could finish the lines with \n\t - the lines
preceding labels only with \n - so that the asm output looks readable.
Right now it is a single line of instructions. But I can fix that later.
---
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -33,23 +33,23 @@
* trap should their return address end up getting used, in a loop.
*/
#define __FILL_RETURN_BUFFER(reg, nr, sp) \
- mov $(nr/2), reg; \
-771: \
- call 772f; \
-773: /* speculation trap */ \
- pause; \
- lfence; \
- jmp 773b; \
-772: \
- call 774f; \
-775: /* speculation trap */ \
- pause; \
- lfence; \
- jmp 775b; \
-774: \
- dec reg; \
- jnz 771b; \
- add $(BITS_PER_LONG/8) * nr, sp;
+ mov $(nr/2), reg\n \
+771:\n\t \
+ call 772f\n \
+773:/* speculation trap */\n\t \
+ pause\n\t \
+ lfence\n\t \
+ jmp 773b\n \
+772:\n\t \
+ call 774f\n \
+775: /* speculation trap */\n\t \
+ pause\n\t \
+ lfence\n\t \
+ jmp 775b\n \
+774:\n\t \
+ dec reg\n\t \
+ jnz 771b\n\t \
+ add $(BITS_PER_LONG/8) * nr, sp\n
#ifdef __ASSEMBLY__
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2018-01-14 15:36 UTC|newest]
Thread overview: 85+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-11 21:46 [PATCH v8 00/12] Retpoline: Avoid speculative indirect calls in kernel David Woodhouse
2018-01-11 21:46 ` [PATCH v8 01/12] objtool: Detect jumps to retpoline thunks David Woodhouse
2018-01-11 23:22 ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-11 21:46 ` [PATCH v8 02/12] objtool: Allow alternatives to be ignored David Woodhouse
2018-01-11 23:22 ` [tip:x86/pti] " tip-bot for Josh Poimboeuf
2018-01-18 19:09 ` [v8,02/12] " Guenter Roeck
2018-01-18 19:33 ` Josh Poimboeuf
2018-01-18 19:41 ` Guenter Roeck
2018-01-22 19:34 ` David Woodhouse
2018-01-22 20:25 ` Guenter Roeck
2018-01-22 20:27 ` David Woodhouse
2018-01-28 21:06 ` Josh Poimboeuf
2018-01-29 1:26 ` Guenter Roeck
2018-01-29 17:15 ` Guenter Roeck
2018-01-29 17:30 ` Josh Poimboeuf
2018-01-22 19:27 ` Guenter Roeck
2018-01-11 21:46 ` [PATCH v8 03/12] x86/retpoline: Add initial retpoline support David Woodhouse
2018-01-11 23:23 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 23:58 ` [PATCH v8 03/12] " Tom Lendacky
2018-01-12 10:28 ` David Woodhouse
2018-01-12 14:02 ` Tom Lendacky
2018-01-14 15:02 ` Borislav Petkov
2018-01-14 15:53 ` Josh Poimboeuf
2018-01-14 15:59 ` Borislav Petkov
2018-01-11 21:46 ` [PATCH v8 04/12] x86/spectre: Add boot time option to select Spectre v2 mitigation David Woodhouse
2018-01-11 23:23 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-23 22:40 ` [PATCH v8 04/12] " Borislav Petkov
2018-01-23 22:53 ` David Woodhouse
2018-01-23 23:05 ` Andi Kleen
2018-01-23 22:55 ` Jiri Kosina
2018-01-23 23:05 ` Borislav Petkov
2018-01-24 0:32 ` Kees Cook
2018-01-24 9:58 ` Borislav Petkov
2018-01-23 23:06 ` Jiri Kosina
2018-01-23 23:21 ` Andi Kleen
2018-01-23 23:24 ` Jiri Kosina
2018-01-23 23:45 ` Andi Kleen
2018-01-23 23:49 ` Jiri Kosina
2018-01-24 4:26 ` Greg Kroah-Hartman
2018-01-24 9:56 ` Jiri Kosina
2018-01-24 13:58 ` Greg Kroah-Hartman
2018-01-24 14:03 ` Jiri Kosina
2018-01-24 14:22 ` Greg Kroah-Hartman
2018-01-11 21:46 ` [PATCH v8 05/12] x86/retpoline/crypto: Convert crypto assembler indirect jumps David Woodhouse
2018-01-11 23:24 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 06/12] x86/retpoline/entry: Convert entry " David Woodhouse
2018-01-11 23:24 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 07/12] x86/retpoline/ftrace: Convert ftrace " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 08/12] x86/retpoline/hyperv: Convert " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 09/12] x86/retpoline/xen: Convert Xen hypercall " David Woodhouse
2018-01-11 23:25 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 10/12] x86/retpoline/checksum32: Convert assembler " David Woodhouse
2018-01-11 23:26 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 21:46 ` [PATCH v8 11/12] x86/retpoline/irq32: " David Woodhouse
2018-01-11 23:26 ` [tip:x86/pti] " tip-bot for Andi Kleen
2018-01-11 21:46 ` [PATCH v8 12/12] x86/retpoline: Fill return stack buffer on vmexit David Woodhouse
2018-01-11 23:27 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-11 23:51 ` [PATCH v8 12/12] " Andi Kleen
2018-01-12 11:11 ` [PATCH v8.1 " David Woodhouse
2018-01-12 11:15 ` Thomas Gleixner
2018-01-12 11:21 ` Woodhouse, David
2018-01-12 11:37 ` [tip:x86/pti] " tip-bot for David Woodhouse
2018-01-14 14:50 ` Borislav Petkov
2018-01-14 15:28 ` Thomas Gleixner
2018-01-14 15:35 ` Borislav Petkov [this message]
2018-01-25 12:07 ` Borislav Petkov
2018-01-25 12:20 ` David Woodhouse
2018-01-25 12:45 ` Borislav Petkov
2018-01-25 15:10 ` Josh Poimboeuf
2018-01-25 15:51 ` Borislav Petkov
2018-01-25 16:03 ` David Woodhouse
2018-01-25 16:56 ` Josh Poimboeuf
2018-01-25 17:00 ` David Woodhouse
2018-01-25 17:05 ` Andy Lutomirski
2018-01-25 17:44 ` Josh Poimboeuf
2018-01-25 18:41 ` Jiri Kosina
2018-01-25 17:10 ` Thomas Gleixner
2018-01-25 17:32 ` Josh Poimboeuf
2018-01-25 17:53 ` Borislav Petkov
2018-01-25 18:04 ` David Woodhouse
2018-01-25 18:32 ` Josh Poimboeuf
2018-01-25 19:07 ` Borislav Petkov
2018-01-25 19:10 ` Borislav Petkov
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