From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=OEyd=Y4=lists.openwall.com=kernel-hardening-return-17259-kernel-hardening=archiver.kernel.org@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-6.3 required=3.0
	tests=BUG6152_INVALID_DATE_TZ_ABSURD,INCLUDES_PATCH,INVALID_DATE_TZ_ABSURD,
	MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED
	autolearn=unavailable autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 3D02ECA9EB5
	for <kernel-hardening@archiver.kernel.org>; Mon,  4 Nov 2019 13:21:14 +0000 (UTC)
Received: from mother.openwall.net (mother.openwall.net [195.42.179.200])
	by mail.kernel.org (Postfix) with SMTP id 9523421D7D
	for <kernel-hardening@archiver.kernel.org>; Mon,  4 Nov 2019 13:21:13 +0000 (UTC)
DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9523421D7D
Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org
Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17259-kernel-hardening=archiver.kernel.org@lists.openwall.com
Received: (qmail 3134 invoked by uid 550); 4 Nov 2019 13:21:07 -0000
Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm
Precedence: bulk
List-Post: <mailto:kernel-hardening@lists.openwall.com>
List-Help: <mailto:kernel-hardening-help@lists.openwall.com>
List-Unsubscribe: <mailto:kernel-hardening-unsubscribe@lists.openwall.com>
List-Subscribe: <mailto:kernel-hardening-subscribe@lists.openwall.com>
List-ID: <kernel-hardening.lists.openwall.com>
Received: (qmail 3114 invoked from network); 4 Nov 2019 13:21:07 -0000
To: Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH v4 13/17] arm64: preserve x18 when CPU is suspended
X-PHP-Originating-Script: 0:main.inc
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8;
 format=flowed
Content-Transfer-Encoding: 7bit
Date: Mon, 04 Nov 2019 14:29:59 +0109
From: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>, Catalin Marinas
 <catalin.marinas@arm.com>, Steven Rostedt <rostedt@goodmis.org>, Masami
 Hiramatsu <mhiramat@kernel.org>, Ard Biesheuvel <ard.biesheuvel@linaro.org>,
 Dave Martin <dave.martin@arm.com>, Kees Cook <keescook@chromium.org>, Laura
 Abbott <labbott@redhat.com>, Mark Rutland <mark.rutland@arm.com>, Nick
 Desaulniers <ndesaulniers@google.com>, Jann Horn <jannh@google.com>, Miguel
 Ojeda <miguel.ojeda.sandonis@gmail.com>, Masahiro Yamada
 <yamada.masahiro@socionext.com>, <clang-built-linux@googlegroups.com>,
 <kernel-hardening@lists.openwall.com>,
 <linux-arm-kernel@lists.infradead.org>, <linux-kernel@vger.kernel.org>
In-Reply-To: <20191101221150.116536-14-samitolvanen@google.com>
References: <20191018161033.261971-1-samitolvanen@google.com>
 <20191101221150.116536-1-samitolvanen@google.com>
 <20191101221150.116536-14-samitolvanen@google.com>
Message-ID: <02c56a5273f94e9d832182f1b3cb5097@www.loen.fr>
X-Sender: maz@kernel.org
User-Agent: Roundcube Webmail/0.7.2
X-SA-Exim-Connect-IP: <locally generated>
X-SA-Exim-Rcpt-To: samitolvanen@google.com, will@kernel.org, catalin.marinas@arm.com, rostedt@goodmis.org, mhiramat@kernel.org, ard.biesheuvel@linaro.org, dave.martin@arm.com, keescook@chromium.org, labbott@redhat.com, mark.rutland@arm.com, ndesaulniers@google.com, jannh@google.com, miguel.ojeda.sandonis@gmail.com, yamada.masahiro@socionext.com, clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
X-SA-Exim-Mail-From: maz@kernel.org
X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false

On 2019-11-01 23:21, Sami Tolvanen wrote:
> Don't lose the current task's shadow stack when the CPU is suspended.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
>  arch/arm64/include/asm/suspend.h |  2 +-
>  arch/arm64/mm/proc.S             | 10 ++++++++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/suspend.h
> b/arch/arm64/include/asm/suspend.h
> index 8939c87c4dce..0cde2f473971 100644
> --- a/arch/arm64/include/asm/suspend.h
> +++ b/arch/arm64/include/asm/suspend.h
> @@ -2,7 +2,7 @@
>  #ifndef __ASM_SUSPEND_H
>  #define __ASM_SUSPEND_H
>
> -#define NR_CTX_REGS 12
> +#define NR_CTX_REGS 13
>  #define NR_CALLEE_SAVED_REGS 12
>
>  /*
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index fdabf40a83c8..5616dc52a033 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -49,6 +49,8 @@
>   * cpu_do_suspend - save CPU registers context
>   *
>   * x0: virtual address of context pointer
> + *
> + * This must be kept in sync with struct cpu_suspend_ctx in 
> <asm/suspend.h>.
>   */
>  ENTRY(cpu_do_suspend)
>  	mrs	x2, tpidr_el0
> @@ -73,6 +75,9 @@ alternative_endif
>  	stp	x8, x9, [x0, #48]
>  	stp	x10, x11, [x0, #64]
>  	stp	x12, x13, [x0, #80]
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +	str	x18, [x0, #96]
> +#endif

Do we need the #ifdefery here? We didn't add that to the KVM path,
and I'd feel better having a single behaviour, specially when
NR_CTX_REGS is unconditionally sized to hold 13 regs.

>  	ret
>  ENDPROC(cpu_do_suspend)
>
> @@ -89,6 +94,11 @@ ENTRY(cpu_do_resume)
>  	ldp	x9, x10, [x0, #48]
>  	ldp	x11, x12, [x0, #64]
>  	ldp	x13, x14, [x0, #80]
> +#ifdef CONFIG_SHADOW_CALL_STACK
> +	ldr	x18, [x0, #96]
> +	/* Clear the SCS pointer from the state buffer */
> +	str	xzr, [x0, #96]
> +#endif
>  	msr	tpidr_el0, x2
>  	msr	tpidrro_el0, x3
>  	msr	contextidr_el1, x4

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...