Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752074AbbHRAHM (ORCPT ); Mon, 17 Aug 2015 20:07:12 -0400 Received: from terminus.zytor.com ([198.137.202.10]:56874 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751050AbbHRAHL (ORCPT ); Mon, 17 Aug 2015 20:07:11 -0400 User-Agent: K-9 Mail for Android In-Reply-To: References: <20150814071500.GA2678@gmail.com> <20150817080143.GA16928@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Subject: Re: [GIT PULL] x86 fixes From: "H. Peter Anvin" Date: Mon, 17 Aug 2015 17:06:46 -0700 To: Andy Lutomirski , Ingo Molnar CC: Linus Torvalds , Juergen Gross , Andy Lutomirski , Linux Kernel Mailing List , Thomas Gleixner , Peter Zijlstra , Brian Gerst , Denys Vlasenko , Andrew Morton Message-ID: <3019C0BF-A7B4-4058-8F92-A6104FE41E1D@zytor.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1283 Lines: 31 User space does not need to treat for FPU instructions, except for performance reasons, because the kernel emulates the full x87 FPU. So it is localized to the kernel. On August 17, 2015 4:59:18 PM PDT, Andy Lutomirski wrote: >On Mon, Aug 17, 2015 at 1:01 AM, Ingo Molnar wrote: >> So when I re-introduced static allocations math-emu started working >again, to a >> limited degree: on a modern distro, trying to boot /bin/bash I got a >prompt, but >> various programs would segfault. I did not investigate it any deeper, >I suppose >> the FPU emulation does not go far enough for modern user-space, or >maybe it has >> more bugs. >> > >Were you testing with just no387 or did you run a VM with SSE2 and >such turned off? > >There's a *lot* of userspace that incorrectly checks for instructions >without checking for the state support. I've filed bugs against >libgcc for this and they're still not fixed IIRC. > >--Andy -- Sent from my Android device with K-9 Mail. Please excuse my brevity. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/