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 5C857C38A2D for ; Mon, 24 Oct 2022 12:21:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233392AbiJXMVa (ORCPT ); Mon, 24 Oct 2022 08:21:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233471AbiJXMTk (ORCPT ); Mon, 24 Oct 2022 08:19:40 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 009D97B5AD; Mon, 24 Oct 2022 04:58:11 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9EA95D6E; Mon, 24 Oct 2022 04:56:16 -0700 (PDT) Received: from FVFF77S0Q05N (unknown [10.57.7.186]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6A90F3F7B4; Mon, 24 Oct 2022 04:56:06 -0700 (PDT) Date: Mon, 24 Oct 2022 12:56:03 +0100 From: Mark Rutland To: Guo Ren , peterz@infradead.org Cc: Lai Jiangshan , arnd@arndb.de, palmer@rivosinc.com, tglx@linutronix.de, luto@kernel.org, conor.dooley@microchip.com, heiko@sntech.de, jszhang@kernel.org, lazyparser@gmail.com, falcon@tinylab.org, chenhuacai@kernel.org, apatel@ventanamicro.com, atishp@atishpatra.org, palmer@dabbelt.com, paul.walmsley@sifive.com, zouyipeng@huawei.com, bigeasy@linutronix.de, David.Laight@aculab.com, chenzhongjin@huawei.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, Borislav Petkov , Miguel Ojeda , Kees Cook , Nick Desaulniers Subject: Re: [PATCH V6 04/11] compiler_types.h: Add __noinstr_section() for noinstr Message-ID: References: <20221002012451.2351127-1-guoren@kernel.org> <20221002012451.2351127-5-guoren@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 20, 2022 at 08:29:28PM +0800, Guo Ren wrote: > Hi Mark and Lai, > > On Thu, Oct 20, 2022 at 5:15 PM Mark Rutland wrote: > > > > On Sat, Oct 08, 2022 at 09:54:39AM +0800, Guo Ren wrote: > > > On Mon, Oct 3, 2022 at 7:39 PM Mark Rutland wrote: > > > > > > > > On Sat, Oct 01, 2022 at 09:24:44PM -0400, guoren@kernel.org wrote: > > > > > From: Lai Jiangshan > > > > > > > > > > And it will be extended for C entry code. > > > > > > > > > > Cc: Borislav Petkov > > > > > Reviewed-by: Miguel Ojeda > > > > > Reviewed-by: Kees Cook > > > > > Suggested-by: Nick Desaulniers > > > > > Suggested-by: Peter Zijlstra > > > > > Signed-off-by: Lai Jiangshan > > > > > --- > > > > > include/linux/compiler_types.h | 8 +++++--- > > > > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > > > > > > > diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h > > > > > index 4f2a819fd60a..e9ce11ea4d8b 100644 > > > > > --- a/include/linux/compiler_types.h > > > > > +++ b/include/linux/compiler_types.h > > > > > @@ -227,9 +227,11 @@ struct ftrace_likely_data { > > > > > #endif > > > > > > > > > > /* Section for code which can't be instrumented at all */ > > > > > -#define noinstr \ > > > > > - noinline notrace __attribute((__section__(".noinstr.text"))) \ > > > > > - __no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage > > > > > +#define __noinstr_section(section) \ > > > > > + noinline notrace __section(section) __no_profile \ > > > > > + __no_kcsan __no_sanitize_address __no_sanitize_coverage > > > > > + > > > > > +#define noinstr __noinstr_section(".noinstr.text") > > > > > > > > One thing proably worth noting here is that while KPROBES will avoid > > > > instrumenting `.noinstr.text`, that won't happen automatically for other > > > > __noinstr_section() sections, and that will need to be inhibited through other > > > > means (e.g. the kprobes blacklist, explicit NOKPROBE_SYMBOL() annotation, or > > > > otherwise). > > > > > > In riscv, "we select HAVE_KPROBES if !XIP_KERNEL", so don't worry > > > about that. I don't think we could enable kprobe for XIP_KERNEL in the > > > future. > > > > Sure; but someone else might use __noinstr_section() elsewhere where this could > > matter, and I was suggesting that we could add a comment as above. > Okay, how about: > > /* Be care KPROBES will avoid instrumenting .noinstr.text, not > __noinstr_section(). */ > #define __noinstr_section(section) \ > noinline notrace __section(section) __no_profile \ > __no_kcsan __no_sanitize_address __no_sanitize_coverage How about we split this like: | /* | * Prevent the compiler from instrumenting this code in any way | * This does not prevent instrumentation via KPROBES, which must be | * prevented through other means if necessary. | */ | #define __no_compiler_instrument \ | noinline notrace noinline notrace __no_kcsan \ | __no_sanitize_address __no_sanitize_coverage | | /* | * Section for code which can't be instrumented at all. | * Any code in this section cannot be instrumented with KPROBES. | */ | #define noinstr __no_compiler_instrument section(".noinstr.text") ... then we don't need __noinstr_section(), and IMO the split is clearer. Peter? Thanks, Mark.