From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 22126C33CB6 for ; Thu, 16 Jan 2020 17:42:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE7EC24695 for ; Thu, 16 Jan 2020 17:42:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579196574; bh=mgprMcwg5geRqmgaKiU1wuHYHMykWSduBoXMRAfD5oU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=uOsuv6vMAXsyB+cUH1rn5BH15mGGFXbr+hGBO+LorCGqeWqbFm4MXNQ1Cgzizfd3C EvbA8GSbF/QIMEpuh7w7SKcLeS2mpByqMTBYTKVZM3LpRzvkDGFRpmH23WIv9BwroG 2Cht/mL5StBh4gvi+hM+MlzLcKKzeBmwVN+OXBEM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405854AbgAPRmx (ORCPT ); Thu, 16 Jan 2020 12:42:53 -0500 Received: from mail.kernel.org ([198.145.29.99]:60506 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393828AbgAPRmc (ORCPT ); Thu, 16 Jan 2020 12:42:32 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DBF40246A4; Thu, 16 Jan 2020 17:42:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579196551; bh=mgprMcwg5geRqmgaKiU1wuHYHMykWSduBoXMRAfD5oU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Mgw6egZbi23SsHpczLIWPA2oAwGPyk1eHd0VM6m9t7cbSHqf6wpmF1ExXLBq+pIoS ao91bTU+o5nHjuJ5t+13jNG0TuB8o3S23+d9VEpLJq1SU98zND0ETuVrwom6LsbauM AfXlJFTytG/yjer33m8X2wJA8Wvp2M4SU906Ij2A= Date: Thu, 16 Jan 2020 17:42:25 +0000 From: Will Deacon To: Sami Tolvanen Cc: Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Mark Rutland , Dave Martin , Kees Cook , Laura Abbott , Marc Zyngier , Nick Desaulniers , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux@googlegroups.com, kernel-hardening@lists.openwall.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 10/15] arm64: preserve x18 when CPU is suspended Message-ID: <20200116174225.GC21396@willie-the-truck> References: <20191018161033.261971-1-samitolvanen@google.com> <20191206221351.38241-1-samitolvanen@google.com> <20191206221351.38241-11-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191206221351.38241-11-samitolvanen@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 06, 2019 at 02:13:46PM -0800, Sami Tolvanen wrote: > Don't lose the current task's shadow stack when the CPU is suspended. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Nick Desaulniers > Reviewed-by: Kees Cook > Reviewed-by: Mark Rutland > --- > arch/arm64/include/asm/suspend.h | 2 +- > arch/arm64/mm/proc.S | 14 ++++++++++++++ > 2 files changed, 15 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..5c8219c55948 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 . > */ > ENTRY(cpu_do_suspend) > mrs x2, tpidr_el0 > @@ -73,6 +75,11 @@ alternative_endif > stp x8, x9, [x0, #48] > stp x10, x11, [x0, #64] > stp x12, x13, [x0, #80] > + /* > + * Save x18 as it may be used as a platform register, e.g. by shadow > + * call stack. > + */ > + str x18, [x0, #96] > ret > ENDPROC(cpu_do_suspend) > > @@ -89,6 +96,13 @@ ENTRY(cpu_do_resume) > ldp x9, x10, [x0, #48] > ldp x11, x12, [x0, #64] > ldp x13, x14, [x0, #80] > + /* > + * Restore x18, as it may be used as a platform register, and clear > + * the buffer to minimize the risk of exposure when used for shadow > + * call stack. > + */ > + ldr x18, [x0, #96] > + str xzr, [x0, #96] Mumble, mumble, spectre-v4. But I think it's fairly hopeless trying to fix that everywhere it crops up, so: Acked-by: Will Deacon Will