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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 063EAC433F5 for ; Wed, 23 Feb 2022 09:06:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232651AbiBWJGf (ORCPT ); Wed, 23 Feb 2022 04:06:35 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230301AbiBWJGf (ORCPT ); Wed, 23 Feb 2022 04:06:35 -0500 Received: from out30-45.freemail.mail.aliyun.com (out30-45.freemail.mail.aliyun.com [115.124.30.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E39557B35; Wed, 23 Feb 2022 01:06:06 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R931e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04407;MF=ashimida@linux.alibaba.com;NM=1;PH=DS;RN=20;SR=0;TI=SMTPD_---0V5I3avg_1645607161; Received: from 192.168.193.152(mailfrom:ashimida@linux.alibaba.com fp:SMTPD_---0V5I3avg_1645607161) by smtp.aliyun-inc.com(127.0.0.1); Wed, 23 Feb 2022 17:06:02 +0800 Message-ID: Date: Wed, 23 Feb 2022 01:06:01 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.0 Subject: Re: [PATCH] [PATCH] AARCH64: Add gcc Shadow Call Stack support Content-Language: en-US To: Mark Rutland Cc: catalin.marinas@arm.com, will@kernel.org, nathan@kernel.org, ndesaulniers@google.com, keescook@chromium.org, masahiroy@kernel.org, tglx@linutronix.de, akpm@linux-foundation.org, samitolvanen@google.com, npiggin@gmail.com, linux@roeck-us.net, mhiramat@kernel.org, ojeda@kernel.org, luc.vanoostenryck@gmail.com, elver@google.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, llvm@lists.linux.dev, linux-hardening@vger.kernel.org References: <20220222095736.24898-1-ashimida@linux.alibaba.com> From: Dan Li In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On 2/22/22 10:47, Mark Rutland wrote: > Hi, > > On Tue, Feb 22, 2022 at 01:57:36AM -0800, Dan Li wrote: >> Shadow call stack is available in GCC > 11.2.0, this patch makes >> the corresponding kernel configuration available when compiling >> the kernel with gcc. > > Neat! > > My local GCC devs told me that means GCC 12.x.x rather than 11.2.x or > 11.3.x, so as others have said it'd be clearer to say `GCC >= 12.0.0`. > Ah, yes, I just saw this flag in gcc/BASE-VER. > I'd like to try this with a GCC binary before I provide an Ack or R-b; > but in the mean time I have a few comments below. > Thanks for your test, Mark. Please let me know if there is any issues :) >> --- >> FYI: >> This function can be used to test if the shadow call stack works: >> //noinline void __noscs scs_test(void) >> noinline void scs_test(void) >> { >> register unsigned long *sp asm("sp"); >> unsigned long * lr = sp + 1; >> >> asm volatile("":::"x30"); >> *lr = 0; >> } > > It's probably be better to use __builtin_frame_address(0) to get the > address of the frame record rather than assuming that fp==sp in the > middle of the function. > Got it. >> config SHADOW_CALL_STACK >> - bool "Clang Shadow Call Stack" >> - depends on CC_IS_CLANG && ARCH_SUPPORTS_SHADOW_CALL_STACK >> + bool "Shadow Call Stack" >> + depends on ARCH_SUPPORTS_SHADOW_CALL_STACK >> depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER >> help >> - This option enables Clang's Shadow Call Stack, which uses a >> + This option enables Clang/GCC's Shadow Call Stack, which uses a >> shadow stack to protect function return addresses from being >> overwritten by an attacker. More information can be found in >> Clang's documentation: > > Is there any additional GCC documentation that we can refer to? > Currently there is only a brief description of -fsanitize=shadow-call-stack in the user manual. Since the description of the clang documentation is more detailed, should I add this gcc link to the configuration description? Link: https://gcc.gnu.org/onlinedocs/gcc/Instrumentation-Options.html#Instrumentation-Options >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 09b885cc4db5..a48a604301aa 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -1255,7 +1255,7 @@ config HW_PERF_EVENTS >> config ARCH_HAS_FILTER_PGPROT >> def_bool y >> >> -# Supported by clang >= 7.0 >> +# Supported by clang >= 7.0 or GCC > 11.2.0 > > As above, I beleive that should be `GCC >= 12.0.0`. > Yeah. Thanks, Dan.