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d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=7SvlubfnETv6Lqsqt46/5KWRbZ29odbFQDS36wzk3F4=; b=DxQ0KMxSd7tMeCUfAB/RpdrP8GPJKMFONlbIojmRk9eI6tJo6IIkRIDN7my/46gxB0 vYwanIHHrFV3+bqZRfTdCgnSZJP+nU5TqUTgSAmdRk2h1+Nf1rzV3xOfGyUqGd0IQFEF Ld2wuVVcz1TXfnf1OR5a5ns7kDgZXqG3xCmHJr4qEXhKeZL4dOpA7Yah58yNx3vMq//w CzxywSiECkcYJ5rJOnkb3+dy7M4NW8eNMTdK72hAzqLVirAoHH4pRQYSUSKwCyjvI1WA c1hljxixaoVHc1W3kmJSoAHXORDbk++2UNR4ZBk3RHOfsyijDTgjgHZJdyjLQXU4L3D3 QD0w== X-Gm-Message-State: AJIora9LPHv/a8+rY2imEHHnuAU4Ume+oPPCs2FA9oz3pGHC3/Pz+qE/ sFE7ktWM5/gmtHJ6fdl/ZADIE3WvVpb9B5lxmSmJRQ== X-Google-Smtp-Source: AGRyM1v36Q48RJE6uKdeYmUlVCUbpTuH7bl+Du66lKP9Xu2bhucDK3uya1dq4QjNCJVsfTYFeq75DjLNNWDuh5RjQVw= X-Received: by 2002:a05:600c:4fd0:b0:39c:6565:31a5 with SMTP id o16-20020a05600c4fd000b0039c656531a5mr17123862wmq.60.1656668617649; Fri, 01 Jul 2022 02:43:37 -0700 (PDT) MIME-Version: 1.0 References: <20220630080834.2742777-1-davidgow@google.com> <20220630080834.2742777-2-davidgow@google.com> <20220630125434.GA20153@axis.com> <20220701091653.GA7009@axis.com> In-Reply-To: <20220701091653.GA7009@axis.com> From: David Gow Date: Fri, 1 Jul 2022 17:43:26 +0800 Message-ID: Subject: Re: [PATCH v4 2/2] UML: add support for KASAN under x86_64 To: Vincent Whitchurch Cc: Andrey Konovalov , Dmitry Vyukov , Johannes Berg , Patricia Alfonso , Jeff Dike , Richard Weinberger , "anton.ivanov@cambridgegreys.com" , Brendan Higgins , Andrew Morton , Andrey Ryabinin , kasan-dev , "linux-um@lists.infradead.org" , LKML , Daniel Latypov , "linux-mm@kvack.org" , "kunit-dev@googlegroups.com" Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha-256; boundary="0000000000007b69fc05e2bb3865" ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656668619; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=7SvlubfnETv6Lqsqt46/5KWRbZ29odbFQDS36wzk3F4=; b=thmS7Z9fJ5N/G93FWHpdqzL+LOt+oCyZhfG5TT2612o84xMWHuUlZR5GtC5TXgU2alLGKt z45kHG9WlbYrtg4buam492bQoCmCl7Rnq9Tx/hN0SyZooREvqdrkxkQeCwsPRCIBn04Lh/ OBbH/yDo9Rz0aaAwVbNnkQY2fQhMJLY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656668619; a=rsa-sha256; cv=none; b=3LWrNh4b0r0gj+MZKHvn63KvxJShbym+pDjiO5IWpPU9PVip6FynnBpAXA+eea8ZtDhV96 V5mQt+MPEbCUWqZ2/8Mbo7x9vD2KQBVzGcFqfPjw3gXFs5knlgI472cZHzLoLMvsHpWafl v+HDnH6QYzlpaXJ+rkl0ziRQwlO9he8= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=SbcQ6RCt; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf11.hostedemail.com: domain of davidgow@google.com designates 209.85.128.49 as permitted sender) smtp.mailfrom=davidgow@google.com X-Stat-Signature: khuxjdus4t5htedqmug48wzs6ss5tmoy X-Rspam-User: Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=SbcQ6RCt; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf11.hostedemail.com: domain of davidgow@google.com designates 209.85.128.49 as permitted sender) smtp.mailfrom=davidgow@google.com X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E451A4004C X-HE-Tag: 1656668618-337469 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: --0000000000007b69fc05e2bb3865 Content-Type: text/plain; charset="UTF-8" On Fri, Jul 1, 2022 at 5:16 PM Vincent Whitchurch wrote: > > On Fri, Jul 01, 2022 at 11:08:27AM +0200, David Gow wrote: > > On Thu, Jun 30, 2022 at 9:29 PM Andrey Konovalov wrote: > > > Stack trace collection code might trigger KASAN splats when walking > > > stack frames, but this can be resolved by using unchecked accesses. > > > The main reason to disable instrumentation here is for performance > > > reasons, see the upcoming patch for arm64 [1] for some details. > > > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?id=802b91118d11 > > > > Ah -- that does it! Using READ_ONCE_NOCHECK() in dump_trace() gets rid > > of the nasty recursive KASAN failures we were getting in the tests. > > > > I'll send out v5 with those files instrumented again. > > Hmm, do we really want that? In the patch Andrey linked to above he > removed the READ_ONCE_NOCHECK() and added the KASAN_SANITIZE on the > corresponding files for arm64, just like it's already the case in this > patch for UML. Personally, I'm okay with the performance overhead so far: in my tests with a collection of ~350 KUnit tests, the total difference in runtime was about ~.2 seconds, and was within the margin of error caused by fluctuations in the compilation time. As an example, without the stacktrace code instrumented: [17:36:50] Testing complete. Passed: 364, Failed: 0, Crashed: 0, Skipped: 47, Errors: 0 [17:36:50] Elapsed time: 15.114s total, 0.003s configuring, 8.518s building, 6.433s running versus with it instrumented: [17:35:40] Testing complete. Passed: 364, Failed: 0, Crashed: 0, Skipped: 47, Errors: 0 [17:35:40] Elapsed time: 15.497s total, 0.003s configuring, 8.691s building, 6.640s running That being said, I'm okay with disabling it again and adding a comment if it's slow enough in some other usecase to cause problems (or even just be annoying). That could either be done in a v6 of this patchset, or a follow-up patch, depending on what people would prefer. But I'd not have a problem with leaving it instrumented for now. -- David --0000000000007b69fc05e2bb3865 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIIPnwYJKoZIhvcNAQcCoIIPkDCCD4wCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg ggz5MIIEtjCCA56gAwIBAgIQeAMYYHb81ngUVR0WyMTzqzANBgkqhkiG9w0BAQsFADBMMSAwHgYD VQQLExdHbG9iYWxTaWduIFJvb3QgQ0EgLSBSMzETMBEGA1UEChMKR2xvYmFsU2lnbjETMBEGA1UE AxMKR2xvYmFsU2lnbjAeFw0yMDA3MjgwMDAwMDBaFw0yOTAzMTgwMDAwMDBaMFQxCzAJBgNVBAYT AkJFMRkwFwYDVQQKExBHbG9iYWxTaWduIG52LXNhMSowKAYDVQQDEyFHbG9iYWxTaWduIEF0bGFz IFIzIFNNSU1FIENBIDIwMjAwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQCvLe9xPU9W dpiHLAvX7kFnaFZPuJLey7LYaMO8P/xSngB9IN73mVc7YiLov12Fekdtn5kL8PjmDBEvTYmWsuQS 6VBo3vdlqqXZ0M9eMkjcKqijrmDRleudEoPDzTumwQ18VB/3I+vbN039HIaRQ5x+NHGiPHVfk6Rx c6KAbYceyeqqfuJEcq23vhTdium/Bf5hHqYUhuJwnBQ+dAUcFndUKMJrth6lHeoifkbw2bv81zxJ 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