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=-18.9 required=3.0 tests=BAYES_00,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, URIBL_BLOCKED,USER_AGENT_SANE_1,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 6B010C43464 for ; Fri, 18 Sep 2020 12:33:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2B2F20874 for ; Fri, 18 Sep 2020 12:32:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="qL4mSxuD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726612AbgIRMc5 (ORCPT ); Fri, 18 Sep 2020 08:32:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726591AbgIRMc5 (ORCPT ); Fri, 18 Sep 2020 08:32:57 -0400 Received: from mail-wm1-x341.google.com (mail-wm1-x341.google.com [IPv6:2a00:1450:4864:20::341]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 389F4C06174A for ; Fri, 18 Sep 2020 05:32:57 -0700 (PDT) Received: by mail-wm1-x341.google.com with SMTP id x23so5157372wmi.3 for ; Fri, 18 Sep 2020 05:32:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=RW3V/7rc9G+S8I7/pZacY9c5WPGbtuzmcvpRc7I+JUM=; b=qL4mSxuDrjxuRYOar00dO1llfZRNDUcbTJ+/hSLVke3o6xiH7pVYcSfkiPPz/iDCQj l12QmAeXWvomNGmyC3CHANnT6m9SElltT62xCfL4suFvVzeV3cUcQj1M+T2/NaQWS7ZR /JaufTMWmgCfVgZoGx95s2ud/f4/+U9kn3GjJqPWKaH9wkmZEeTiGEB0RI6xjrn/EsE+ Yj2qNtIBoCjtMhG6ttNdV9JvO0xRSG51NU3/BfNsydJZD5WiEGfFB1KSiynHytnIJ1aB ZohPnzKOsUnnel3D+zfJAaSHxfxFNLe3B6DuOyRrbRy8UD1BPC684QynexNY8tSqwzjP TOtw== 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:user-agent; bh=RW3V/7rc9G+S8I7/pZacY9c5WPGbtuzmcvpRc7I+JUM=; b=Ab0XRAMiEmXjtHvYvDZVsPZiu9M0CbUZkNJvw0U30BlrxRov8lsA3W4cA2tp1kbxk/ 2+wXymbClYrbA7O+gN9B1tPeVY+3QR36qeXqXJmxD8DLwD/Sx+Ocib/KS5rd88AvpX/z BoOD+E34gdbAxkWirXVs0VxdHaM4FN+5fblw6QueISLzB5EMyg7/ffP9cn6KhcBloVoB 18B8qSADQpftKqWpBU6T1SpNYLz/gfLgcWc74hJXuL2IaJ+HQZdL5zOQmnyGEHSnYZJy 2VeMXEXWsHr+U6N4Q9grk8SJWRE7St38ONLKlqnBmFK/ABArJR7b5LBaDG176i8ztujg hxeQ== X-Gm-Message-State: AOAM533ipz/EgOaeaWf5+HQgWKNxfV6PGcJQqhIlq1S4HzqEuAg5d9V/ CQlj/15jXCtCKTszvYuwPj9gaQ== X-Google-Smtp-Source: ABdhPJwA5eQZZD6nEWS4rNGk9gnrwEW+ecPPQhkI9OE6L5VW71FW34+0vWngW8ufMpLjmVkcOjollw== X-Received: by 2002:a1c:7e15:: with SMTP id z21mr15195514wmc.21.1600432375666; Fri, 18 Sep 2020 05:32:55 -0700 (PDT) Received: from elver.google.com ([100.105.32.75]) by smtp.gmail.com with ESMTPSA id y6sm4995614wrt.80.2020.09.18.05.32.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Sep 2020 05:32:54 -0700 (PDT) Date: Fri, 18 Sep 2020 14:32:49 +0200 From: Marco Elver To: Andrey Konovalov Cc: Dmitry Vyukov , Vincenzo Frascino , Catalin Marinas , kasan-dev@googlegroups.com, Andrey Ryabinin , Alexander Potapenko , Evgenii Stepanov , Elena Petrova , Branislav Rankov , Kevin Brodsky , Will Deacon , Andrew Morton , linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 21/37] kasan: introduce CONFIG_KASAN_HW_TAGS Message-ID: <20200918123249.GC2384246@elver.google.com> References: <329ece34759c5208ae32a126dc5c978695ab1776.1600204505.git.andreyknvl@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <329ece34759c5208ae32a126dc5c978695ab1776.1600204505.git.andreyknvl@google.com> User-Agent: Mutt/1.14.4 (2020-06-18) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 15, 2020 at 11:16PM +0200, Andrey Konovalov wrote: > This patch adds a configuration option for a new KASAN mode called > hardware tag-based KASAN. This mode uses the memory tagging approach > like the software tag-based mode, but relies on arm64 Memory Tagging > Extension feature for tag management and access checking. > > Signed-off-by: Andrey Konovalov > Signed-off-by: Vincenzo Frascino > --- > Change-Id: I246c2def9fffa6563278db1bddfbe742ca7bdefe > --- > lib/Kconfig.kasan | 56 +++++++++++++++++++++++++++++++++-------------- > 1 file changed, 39 insertions(+), 17 deletions(-) > > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index b4cf6c519d71..17c9ecfaecb9 100644 > --- a/lib/Kconfig.kasan > +++ b/lib/Kconfig.kasan > @@ -6,7 +6,10 @@ config HAVE_ARCH_KASAN > config HAVE_ARCH_KASAN_SW_TAGS > bool > > -config HAVE_ARCH_KASAN_VMALLOC > +config HAVE_ARCH_KASAN_HW_TAGS > + bool > + > +config HAVE_ARCH_KASAN_VMALLOC > bool > > config CC_HAS_KASAN_GENERIC > @@ -20,10 +23,11 @@ config CC_HAS_WORKING_NOSANITIZE_ADDRESS > > menuconfig KASAN > bool "KASAN: runtime memory debugger" > - depends on (HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ > - (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS) > + depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \ > + (HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \ > + CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \ > + HAVE_ARCH_KASAN_HW_TAGS > depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB) > - depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS > select SLUB_DEBUG if SLUB Is SLUB_DEBUG necessary with HW_TAGS? > select CONSTRUCTORS > select STACKDEPOT > @@ -38,13 +42,18 @@ choice > prompt "KASAN mode" > default KASAN_GENERIC > help > - KASAN has two modes: generic KASAN (similar to userspace ASan, > - x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC) and > - software tag-based KASAN (a version based on software memory > - tagging, arm64 only, similar to userspace HWASan, enabled with > - CONFIG_KASAN_SW_TAGS). > + KASAN has three modes: > + 1. generic KASAN (similar to userspace ASan, > + x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC), > + 2. software tag-based KASAN (arm64 only, based on software > + memory tagging (similar to userspace HWASan), enabled with > + CONFIG_KASAN_SW_TAGS), and > + 3. hardware tag-based KASAN (arm64 only, based on hardware > + memory tagging, enabled with CONFIG_KASAN_HW_TAGS). > > - Both generic and tag-based KASAN are strictly debugging features. > + All KASAN modes are strictly debugging features. > + > + For better error detection enable CONFIG_STACKTRACE. I don't think CONFIG_STACKTRACE improves error detection, right? It only makes the reports more readable > > config KASAN_GENERIC > bool "Generic mode" > @@ -61,8 +70,6 @@ config KASAN_GENERIC > and introduces an overhead of ~x1.5 for the rest of the allocations. > The performance slowdown is ~x3. > > - For better error detection enable CONFIG_STACKTRACE. > - > Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB > (the resulting kernel does not boot). > > @@ -72,9 +79,11 @@ config KASAN_SW_TAGS > help > Enables software tag-based KASAN mode. > > - This mode requires Top Byte Ignore support by the CPU and therefore > - is only supported for arm64. This mode requires Clang version 7.0.0 > - or later. > + This mode require software memory tagging support in the form of > + HWASan-like compiler instrumentation. > + > + Currently this mode is only implemented for arm64 CPUs and relies on > + Top Byte Ignore. This mode requires Clang version 7.0.0 or later. > > This mode consumes about 1/16th of available memory at kernel start > and introduces an overhead of ~20% for the rest of the allocations. > @@ -82,15 +91,27 @@ config KASAN_SW_TAGS > casting and comparison, as it embeds tags into the top byte of each > pointer. > > - For better error detection enable CONFIG_STACKTRACE. > - > Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB > (the resulting kernel does not boot). > > +config KASAN_HW_TAGS > + bool "Hardware tag-based mode" > + depends on HAVE_ARCH_KASAN_HW_TAGS > + depends on SLUB > + help > + Enables hardware tag-based KASAN mode. > + > + This mode requires hardware memory tagging support, and can be used > + by any architecture that provides it. > + > + Currently this mode is only implemented for arm64 CPUs starting from > + ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore. > + > endchoice > > choice > prompt "Instrumentation type" > + depends on KASAN_GENERIC || KASAN_SW_TAGS > default KASAN_OUTLINE > > config KASAN_OUTLINE > @@ -114,6 +135,7 @@ endchoice > > config KASAN_STACK_ENABLE > bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST > + depends on KASAN_GENERIC || KASAN_SW_TAGS > help > The LLVM stack address sanitizer has a know problem that > causes excessive stack usage in a lot of functions, see How about something like the below change (introduce KASAN_INSTRUMENTED Kconfig var) to avoid the repeated "KASAN_GENERIC || KASAN_SW_TAGS". This could then also be used in the various .c/.h files (and make some of the code more readable hopefully). +config KASAN_INSTRUMENTED + def_bool KASAN_GENERIC || KASAN_SW_TAGS + choice prompt "Instrumentation type" - depends on KASAN_GENERIC || KASAN_SW_TAGS + depends on KASAN_INSTRUMENTED default KASAN_OUTLINE config KASAN_OUTLINE @@ -135,7 +141,7 @@ endchoice config KASAN_STACK_ENABLE bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST - depends on KASAN_GENERIC || KASAN_SW_TAGS + depends on KASAN_INSTRUMENTED help The LLVM stack address sanitizer has a know problem that causes excessive stack usage in a lot of functions, see Thanks, -- Marco