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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 88D36CA9EC9 for ; Fri, 1 Nov 2019 03:47:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BBD22067D for ; Fri, 1 Nov 2019 03:47:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=chromium.org header.i=@chromium.org header.b="OUr7ArDi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729757AbfKADrH (ORCPT ); Thu, 31 Oct 2019 23:47:07 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:33309 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726600AbfKADrG (ORCPT ); Thu, 31 Oct 2019 23:47:06 -0400 Received: by mail-pl1-f195.google.com with SMTP id y8so3760783plk.0 for ; Thu, 31 Oct 2019 20:47:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=u5Q9VGAIWgqBExeYcYbdu3s9udgqDxFzlJQ7eRueT/Q=; b=OUr7ArDiqHbONLazU8MgPIGz23M1A8vMM7F8b9Md5DVHQ+EZhCFgoZlMZ+G5HTnpZ+ wE2eqONi9hN3i5Bcrge6nsj37dKyheWOwYi04/RxLQQQWFlzKYDXXwSGgtrWINXpoHTa pu2AouoST0OW8JKhXcovsqIH4Xg7eOJ6N8a30= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=u5Q9VGAIWgqBExeYcYbdu3s9udgqDxFzlJQ7eRueT/Q=; b=tPCXj4hLeOmSHlRxVsmVz7I3rB9MWEJFgT4yYR91Wp9t2ZZ0X9XCSy2dwQsLK4iqg0 3Wu4mK8AlhBGrCspWGEhpJnLiSION6LDloQgbOl2bw/cfi2HbgAkbOeWCL84qQCT66Zc jnJYo29nrZ6yDhhljer3Yq8Jqbe1tJxwQwABANvXpR+LWFx6k+q/HL9ygyb4mXnwhmUU c8jc7Z1vRFGGoSUehI646zDS6EM3AW6q62Ymuejgab58GMeYxk0jnFHX/7EchRU1Y7Hf c2Lka+Jy4nfo0yf7pSSFO9WeEzv58N82AsOBfj051PFWQdD00klLrWuFfDc+4Mt6GykR kwNg== X-Gm-Message-State: APjAAAUtNxHaluHmLd3BycPyqejOzwScXAPXTXlUHWssLa9SGdeSYScn JOMGTKUJB2lWmCStsMlpy4l5EQ== X-Google-Smtp-Source: APXvYqzxXwp35RHwMjtICT5o/o5TX+pRdcY4/XDk99r6vm9qvXrxFtMjtkTLjrDyCFVkkuXacPUM+g== X-Received: by 2002:a17:902:9042:: with SMTP id w2mr10476445plz.323.1572580026099; Thu, 31 Oct 2019 20:47:06 -0700 (PDT) Received: from www.outflux.net (smtp.outflux.net. [198.145.64.163]) by smtp.gmail.com with ESMTPSA id z2sm5943741pgo.13.2019.10.31.20.47.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Oct 2019 20:47:05 -0700 (PDT) Date: Thu, 31 Oct 2019 20:47:04 -0700 From: Kees Cook To: samitolvanen@google.com Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Laura Abbott , Mark Rutland , 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 v3 04/17] arm64: kernel: avoid x18 __cpu_soft_restart Message-ID: <201910312046.53A31D394@keescook> References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> <20191031164637.48901-5-samitolvanen@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191031164637.48901-5-samitolvanen@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 31, 2019 at 09:46:24AM -0700, samitolvanen@google.com wrote: > From: Ard Biesheuvel > > The code in __cpu_soft_restart() uses x18 as an arbitrary temp register, > which will shortly be disallowed. So use x8 instead. > > Link: https://patchwork.kernel.org/patch/9836877/ > Signed-off-by: Ard Biesheuvel This one is easy to validate! ;) Reviewed-by: Kees Cook -Kees > Signed-off-by: Sami Tolvanen > Reviewed-by: Mark Rutland > --- > arch/arm64/kernel/cpu-reset.S | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S > index 6ea337d464c4..32c7bf858dd9 100644 > --- a/arch/arm64/kernel/cpu-reset.S > +++ b/arch/arm64/kernel/cpu-reset.S > @@ -42,11 +42,11 @@ ENTRY(__cpu_soft_restart) > mov x0, #HVC_SOFT_RESTART > hvc #0 // no return > > -1: mov x18, x1 // entry > +1: mov x8, x1 // entry > mov x0, x2 // arg0 > mov x1, x3 // arg1 > mov x2, x4 // arg2 > - br x18 > + br x8 > ENDPROC(__cpu_soft_restart) > > .popsection > -- > 2.24.0.rc0.303.g954a862665-goog > -- Kees Cook