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=-14.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 48FAECA9ECB for ; Thu, 31 Oct 2019 17:11:47 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 8F3B72053B for ; Thu, 31 Oct 2019 17:11:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="Jy/SacxJ" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8F3B72053B Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17203-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 26182 invoked by uid 550); 31 Oct 2019 17:11:40 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 26160 invoked from network); 31 Oct 2019 17:11:39 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=b0X5YfN75r7PDdNJxvGQlnZAXFwdwuMLiQ3l0U13bDg=; b=Jy/SacxJhf/Nbsx+JKEbMsxTmi9nTvRx9QrYmlIIdjaRaYWNvdZdUveUzeL7wIBsMZ yB8Nz5UMhco8wy0o9k2IWrgIZlOKbDsMBdp3atJjR2eE50+zYjEZBM7mTKuaEMqSUi91 ueCuaeZ6gpnfO9SKoIhfR/pmAwffakughLyHWB5/OC9EGvGmL4MkTswLiMaKPF11fEWK w0yeyTRVppcLDoCs0H8aL/rz2ddY3Gr0oQA89wXCPpwffH+YyILuj3R30CX+hlyoHfZ7 WFIUgANql15NGTPB5eu58+Vz5mden9xZ/hmIuvN0j6C6tSpO51yEvLSx5eUFDkhOQhtj fI9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=b0X5YfN75r7PDdNJxvGQlnZAXFwdwuMLiQ3l0U13bDg=; b=pFmN+vLyY/bZ8VIAu/4WuEE3K5wpuJt9NvPhm8B1DxQFhvac2k+0oHf27sn+bx8MAq S6dolYrV2AsGCMpPMf3GyO3+iaEBGIFSgLWsdwXGUiNP7i0SQM46dqUcxY3ko+xvZZOI YrCkHEFJWVrsEsRtsg01x1s2iyYk1Ku0IAgrDFowhcEaL50SdUMGU3gN5fvopwoHsU2P jHrY5uN1T91ZBrbI17xfNTUShouSrW7CTP8WqfyppzHAJxVryHT4q4/wLS3eb5srrvU7 DeOgTuXa/YVAz4ZGj9cf/xh7LQZ/VtSnW8LFgKT79flnj6+PAY7OrNKCiaHKPxMq2Rjy xXEg== X-Gm-Message-State: APjAAAUwBlK1N1QdlW5/9qXhDkcf2ioDHLrgAWBevDULsn3vUQGjK3Y1 EolWcoFg2FE+VAyuoka4Cw9GYigrOQY34W3gwVx3QA== X-Google-Smtp-Source: APXvYqyggyEISFvRqnEZ0+/A7Iby9Fs7Q+2KDnPlM3xak8otQQ4zH05zLjAp9ajmSpT131omcbyYgDm2ydz5aTw6/As= X-Received: by 2002:a17:902:b40f:: with SMTP id x15mr3965837plr.119.1572541887443; Thu, 31 Oct 2019 10:11:27 -0700 (PDT) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191031164637.48901-1-samitolvanen@google.com> <20191031164637.48901-13-samitolvanen@google.com> In-Reply-To: <20191031164637.48901-13-samitolvanen@google.com> From: Nick Desaulniers Date: Thu, 31 Oct 2019 10:11:16 -0700 Message-ID: Subject: Re: [PATCH v3 12/17] arm64: reserve x18 from general allocation with SCS To: Sami Tolvanen Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux , Kernel Hardening , Linux ARM , LKML Content-Type: text/plain; charset="UTF-8" On Thu, Oct 31, 2019 at 9:47 AM wrote: > > Reserve the x18 register from general allocation when SCS is enabled, > because the compiler uses the register to store the current task's > shadow stack pointer. Note that all external kernel modules must also be > compiled with -ffixed-x18 if the kernel has SCS enabled. Inline/out-of-line assembly will also need to be careful not to accidentally overwrite the current task's shadow stack pointer. Without automated checking for that, we'll have to rely on a "gentlemen's promise" for code reviewers, though we'd likely hit such a regression with Android+mainline. Reviewed-by: Nick Desaulniers > > Signed-off-by: Sami Tolvanen > --- > arch/arm64/Makefile | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile > index 2c0238ce0551..ef76101201b2 100644 > --- a/arch/arm64/Makefile > +++ b/arch/arm64/Makefile > @@ -72,6 +72,10 @@ stack_protector_prepare: prepare0 > include/generated/asm-offsets.h)) > endif > > +ifeq ($(CONFIG_SHADOW_CALL_STACK), y) > +KBUILD_CFLAGS += -ffixed-x18 > +endif > + > ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) > KBUILD_CPPFLAGS += -mbig-endian > CHECKFLAGS += -D__AARCH64EB__ > -- > 2.24.0.rc0.303.g954a862665-goog > -- Thanks, ~Nick Desaulniers