From owner-freebsd-current@freebsd.org Thu Jan 4 18:51:16 2018 Return-Path: Delivered-To: freebsd-current@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 533FEEAE018 for ; Thu, 4 Jan 2018 18:51:16 +0000 (UTC) (envelope-from jan.kokemueller@gmail.com) Received: from mail-wr0-x22c.google.com (mail-wr0-x22c.google.com [IPv6:2a00:1450:400c:c0c::22c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id D64A27958E for ; Thu, 4 Jan 2018 18:51:15 +0000 (UTC) (envelope-from jan.kokemueller@gmail.com) Received: by mail-wr0-x22c.google.com with SMTP id p6so2390548wrd.0 for ; Thu, 04 Jan 2018 10:51:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=+sewNVnwHl36GsZl7mLuHIsmaJYzN5Tyz8K6Is9tnnA=; b=WkI4V+iiikNisK3yblKb6ZeAkapQr+/faRepJnFRHGxcjZifhwyGTdcL6PdaqWaUdC mFP3nHd+H5O7dKZFFj1YlslA4YFiqCI6eLpq5RvfEUx0eXgpHuSW84xCKAtviz1y2GOO uFGVcijDaEDudCTF7eWnmK6RTA3UiZpfJ4s4mYkBoMAOSvndwkocgsddFYbL/cLSXuxm nmfgFaD1VvDFpFG5CgbUm3tgXDUpaOO7UC8gHprO0btYZOjoSz0oxK/7ZLV5w8r6irdT 3eDAiaYGmF1dN1pMy2x4iddyeumzQBmE7jFE9qx2ZFQ5csZSG0TZESrbQBF4AxAZKtMF 6f3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+sewNVnwHl36GsZl7mLuHIsmaJYzN5Tyz8K6Is9tnnA=; b=Liq22TJVNQzInHTwp1bk6y4A7tHk4l+nzsAZnzkPk1tH9CK5XmDiHkFacPcRdM+DY2 L3ZtDAtFI+P1r6s64joNuO1nantGoM+jGMlLiQUG9x/0zd3+bNWqraRZFB6u0uK7P3p9 KXdn9MXkBdM8Cz8Df/TmlJoQwnSDkiPpBeaBlsaDJ9gwCN3cdLqjl/IkWsPlEklSTFeS TswT8S0XooE9BV7M58EuVTdErftjt2cV9j18VqHXuJiHDyz922ietPTGnmYilSTx/Ahq T+v1pN4laJ5n6dBbZkZ62uVdjPtQ4Tu5OyoaeLZP426KlwzVS17pSiAqsjGMBGhobLFl dtKw== X-Gm-Message-State: AKGB3mLD0psf9h+D2B55xAnK5OyGFtVm9GJPkWhmSFAbGRY+0rYRnLpQ t5SXgCPB30f86TlrWDhHvGUwzg== X-Google-Smtp-Source: ACJfBosgy5rMzdVPDBeyiJmmKEQzQYomJWzzTqEQffLMcPJbWXLqccQcBE8jTvHUihlatBWzy9kg0Q== X-Received: by 10.223.176.131 with SMTP id i3mr495436wra.120.1515091873932; Thu, 04 Jan 2018 10:51:13 -0800 (PST) Received: from [192.168.178.20] (p5B36C250.dip0.t-ipconnect.de. [91.54.194.80]) by smtp.googlemail.com with ESMTPSA id o18sm3193536wrg.59.2018.01.04.10.51.13 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 04 Jan 2018 10:51:13 -0800 (PST) Subject: Re: Intel CPU design flaw - FreeBSD affected? // disabling LDTSC To: "Klaus P. Ohrhallinger" , freebsd-current@freebsd.org References: <9dda0496-be16-35c6-6c45-63d03b218ccb@protected-networks.net> <18376c97-3c0d-49c8-9483-96b95a84f3f1@7he.at> From: =?UTF-8?Q?Jan_Kokem=c3=bcller?= Message-ID: Date: Thu, 4 Jan 2018 19:51:12 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <18376c97-3c0d-49c8-9483-96b95a84f3f1@7he.at> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Jan 2018 18:51:16 -0000 On 04.01.2018 19:23, Klaus P. Ohrhallinger wrote: > All PoC code I have seen today relies on those instructions. > Is there any other way to measure the memory/cache access times ? It is possible to emulate a high resolution counter with a thread that continuously increments a variable [1]. This is the reason why browser vendors are currently disabling the SharedArrayBuffer feature [2]. [1]: https://gist.github.com/ErikAugust/724d4a969fb2c6ae1bbd7b2a9e3d4bb6#gistcomment-2311156 [2]: https://blog.mozilla.org/security/2018/01/03/mitigations-landing-new-class-timing-attack/