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=-23.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL 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 4DC25C433E0 for ; Mon, 8 Feb 2021 18:46:45 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id CE31F64E73 for ; Mon, 8 Feb 2021 18:46:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE31F64E73 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 25D026B0006; Mon, 8 Feb 2021 13:46:44 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 20D436B006C; Mon, 8 Feb 2021 13:46:44 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1264F6B006E; Mon, 8 Feb 2021 13:46:44 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0046.hostedemail.com [216.40.44.46]) by kanga.kvack.org (Postfix) with ESMTP id F15726B0006 for ; Mon, 8 Feb 2021 13:46:43 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id B33D9824999B for ; Mon, 8 Feb 2021 18:46:43 +0000 (UTC) X-FDA: 77795981886.07.pail10_050fc7a27601 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin07.hostedemail.com (Postfix) with ESMTP id 99772181B9DC3 for ; Mon, 8 Feb 2021 18:46:43 +0000 (UTC) X-HE-Tag: pail10_050fc7a27601 X-Filterd-Recvd-Size: 6317 Received: from mail-oo1-f49.google.com (mail-oo1-f49.google.com [209.85.161.49]) by imf20.hostedemail.com (Postfix) with ESMTP for ; Mon, 8 Feb 2021 18:46:43 +0000 (UTC) Received: by mail-oo1-f49.google.com with SMTP id e17so2148737oow.4 for ; Mon, 08 Feb 2021 10:46:43 -0800 (PST) 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=uiy4+L1TKc0lecuM77Q8fHlOhBTJ6Asny2DXxHTJcDo=; b=sCxbX8R2f2bvawMHT3qjLo0h0zjmMVkbthbZc/FGNTuQlti07fDdGZt78TBsutbnQI oCY8HQ3wAvVEQ/T6y7QOVvt9XsrFxDi+cORohR5IvXM3swUFWfH3phMxyt5+CbiaUvsI LkuDmSHFecb/k/x2VI2Rr67mElyyCB5aXzgHmXNJP9OtdxIfTYYz5joOSs3l2FPRuq0T WTwVwprmUQAm8MXf0VOshOtXu1zPaQxD9xAGWlw9P3KPrHroqJ8XfHmCRnvxa71ezi4D vRlTwa/QJDt0uzrC4S0S0HDQkT9SmEO+4kT2ANyC46ddq6KLtrj3VIna4XwyLenGInz8 w+cw== 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=uiy4+L1TKc0lecuM77Q8fHlOhBTJ6Asny2DXxHTJcDo=; b=VJGbkSpClSYm4UGuYWZYvKPzo9PMwCPTzG2pFAi971GkmJQIZNoi9wunyJ5LlMs3zA uY2hbvRHp3M4v3xQFctoTKaAghOzkTLhYOsTGaLJ1Sn/6iA9RmBiJFm+ymYafaGLzUMT pCOi8uqj+wt9xehkRay63PGsNqSP68VYnUVBZDMeiEGWMBRw9MuV9U2H5fhqdfXCACX+ usJMwAiMA3+CcLU8/Ki9dNIKmfHWN0MrgrmTcyVsDhaN/FSivu1zDGllgeDDwCkzCcTP d/CnZ03BLhAYb9tUL9TM3dW2rSDj/KoDNxr1oYX4cfrPRtCdFb8oJ6f/YrFMWagtIWEe kQSA== X-Gm-Message-State: AOAM530/egS8VfESUacgCvvdTF2xW3F6o29EVQ8a+yDapdX3XPpLrPtU qFSBdeYz8IvPVuFTJ3sHo5glmeT3pIjG+hmJ/msSCg== X-Google-Smtp-Source: ABdhPJzKG3qMZs4qHobju9rjHTgVd7yAMQ7y0XNCIsRGy6N0KqdU8kcdVfEX5R+R8I47cBrzDrUM+oTLxEp2nmYQ1K8= X-Received: by 2002:a4a:aa8b:: with SMTP id d11mr10012285oon.36.1612810002329; Mon, 08 Feb 2021 10:46:42 -0800 (PST) MIME-Version: 1.0 References: <6678d77ceffb71f1cff2cf61560e2ffe7bb6bfe9.1612808820.git.andreyknvl@google.com> In-Reply-To: <6678d77ceffb71f1cff2cf61560e2ffe7bb6bfe9.1612808820.git.andreyknvl@google.com> From: Marco Elver Date: Mon, 8 Feb 2021 19:46:30 +0100 Message-ID: Subject: Re: [PATCH] kasan: fix stack traces dependency for HW_TAGS To: Andrey Konovalov Cc: Andrew Morton , Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev , Linux ARM , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 8 Feb 2021 at 19:40, Andrey Konovalov wrote: > > Currently, whether the alloc/free stack traces collection is enabled by > default for hardware tag-based KASAN depends on CONFIG_DEBUG_KERNEL. > The intention for this dependency was to only enable collection on slow > debug kernels due to a significant perf and memory impact. > > As it turns out, CONFIG_DEBUG_KERNEL is not considered a debug option > and is enabled on many productions kernels including Android and Ubuntu. > As the result, this dependency is pointless and only complicates the code > and documentation. > > Having stack traces collection disabled by default would make the hardware > mode work differently to to the software ones, which is confusing. > > This change removes the dependency and enables stack traces collection > by default. > > Looking into the future, this default might makes sense for production > kernels, assuming we implement a fast stack trace collection approach. > > Signed-off-by: Andrey Konovalov Reviewed-by: Marco Elver I'm in favor of this simplification. The fact that CONFIG_DEBUG_KERNEL cannot be relied upon to determine if we're running a debug kernel or not is a bit unfortunate though. Thanks! > --- > Documentation/dev-tools/kasan.rst | 3 +-- > mm/kasan/hw_tags.c | 8 ++------ > 2 files changed, 3 insertions(+), 8 deletions(-) > > diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst > index 1651d961f06a..a248ac3941be 100644 > --- a/Documentation/dev-tools/kasan.rst > +++ b/Documentation/dev-tools/kasan.rst > @@ -163,8 +163,7 @@ particular KASAN features. > - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``). > > - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack > - traces collection (default: ``on`` for ``CONFIG_DEBUG_KERNEL=y``, otherwise > - ``off``). > + traces collection (default: ``on``). > > - ``kasan.fault=report`` or ``=panic`` controls whether to only print a KASAN > report or also panic the kernel (default: ``report``). > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > index e529428e7a11..d558799b25b3 100644 > --- a/mm/kasan/hw_tags.c > +++ b/mm/kasan/hw_tags.c > @@ -134,12 +134,8 @@ void __init kasan_init_hw_tags(void) > > switch (kasan_arg_stacktrace) { > case KASAN_ARG_STACKTRACE_DEFAULT: > - /* > - * Default to enabling stack trace collection for > - * debug kernels. > - */ > - if (IS_ENABLED(CONFIG_DEBUG_KERNEL)) > - static_branch_enable(&kasan_flag_stacktrace); > + /* Default to enabling stack trace collection. */ > + static_branch_enable(&kasan_flag_stacktrace); > break; > case KASAN_ARG_STACKTRACE_OFF: > /* Do nothing, kasan_flag_stacktrace keeps its default value. */ > -- > 2.30.0.478.g8a0d178c01-goog >