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Tue, 8 Sep 2020 14:52:26 +0000 (UTC) IronPort-SDR: beAZRvJp4kXjekyuXZr6JsyYBes+Q3L3YfcoDPJ9Ph1MdMMwQ0f97M6q2i8t4meZY69Nvczczr JUZQVfzsTegQ== X-IronPort-AV: E=McAfee;i="6000,8403,9738"; a="157411457" X-IronPort-AV: E=Sophos;i="5.76,406,1592895600"; d="scan'208";a="157411457" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2020 07:52:24 -0700 IronPort-SDR: cF4qspwrWPTljoE8NCBQQk2v89rOLtcknOBa7JrhGhb9jR0+sbSiSqviGAmBxjGghA5eV08ucx cLguvrY2fPLg== X-IronPort-AV: E=Sophos;i="5.76,406,1592895600"; d="scan'208";a="505096844" Received: from sparasa-mobl1.amr.corp.intel.com (HELO [10.251.10.231]) ([10.251.10.231]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Sep 2020 07:52:22 -0700 Subject: Re: [PATCH RFC 00/10] KFENCE: A low-overhead sampling-based memory safety error detector To: Marco Elver , glider@google.com, akpm@linux-foundation.org, catalin.marinas@arm.com, cl@linux.com, rientjes@google.com, iamjoonsoo.kim@lge.com, mark.rutland@arm.com, penberg@kernel.org Cc: hpa@zytor.com, paulmck@kernel.org, andreyknvl@google.com, aryabinin@virtuozzo.com, luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, dvyukov@google.com, edumazet@google.com, gregkh@linuxfoundation.org, mingo@redhat.com, jannh@google.com, corbet@lwn.net, keescook@chromium.org, peterz@infradead.org, cai@lca.pw, tglx@linutronix.de, will@kernel.org, x86@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org References: <20200907134055.2878499-1-elver@google.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200907134055.2878499-1-elver@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Queue-Id: BE5B618140B72 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam04 Content-Transfer-Encoding: quoted-printable 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 9/7/20 6:40 AM, Marco Elver wrote: > KFENCE is designed to be enabled in production kernels, and has near > zero performance overhead. Compared to KASAN, KFENCE trades performance > for precision.=20 Could you talk a little bit about where you expect folks to continue to use KASAN? How would a developer or a tester choose which one to use? > KFENCE objects each reside on a dedicated page, at either the left or > right page boundaries. The pages to the left and right of the object > page are "guard pages", whose attributes are changed to a protected > state, and cause page faults on any attempted access to them. Such page > faults are then intercepted by KFENCE, which handles the fault > gracefully by reporting a memory access error. How much memory overhead does this end up having? I know it depends on the object size and so forth. But, could you give some real-world examples of memory consumption? Also, what's the worst case? Say I have a ton of worst-case-sized (32b) slab objects. Will I notice?