Date: Mon, 26 Sep 2016 07:09:15 +0000 From: Colin Percival <cperciva@tarsnap.com> To: Bruce Evans <brde@optusnet.com.au> Cc: src-committers@FreeBSD.org, svn-src-all@FreeBSD.org, svn-src-head@FreeBSD.org Subject: Re: svn commit: r306319 - head/sys/i386/i386 Message-ID: <010001576553856d-6d1204e6-9fec-4069-b2ff-96324fea78c6-000000@email.amazonses.com> In-Reply-To: <20160926164406.T806@besplex.bde.org> References: <201609251839.u8PIdO7t050380@repo.freebsd.org> <0100015762ed107c-206ced2e-2389-462f-afe0-cec7d6c34fb8-000000@email.amazonses.com> <20160926164406.T806@besplex.bde.org>
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On 09/25/16 23:53, Bruce Evans wrote: > On Sun, 25 Sep 2016, Colin Percival wrote: >> On 09/25/16 11:39, Bruce Evans wrote: >>> Author: bde >>> Date: Sun Sep 25 18:39:24 2016 >>> New Revision: 306319 >>> URL: https://svnweb.freebsd.org/changeset/base/306319 >>> >>> Log: >>> Minor fixes for 160-bit disassembly: >> >> I thought the x86 architecture was limited to 120-bit instructions? > > Oops. > > Is 120 the exact limit on instruction length is is that just for prefixes? > I think the instruction fetch pipeline was 16 bytes, but it is now often > 32 or 64. Traditionally x86 CPUs would generate an invalid-opcode fault if redundant instruction prefixes resulted in an instruction exceeding 15 bytes. This behaviour might have changed in the past two decades, but I doubt it. -- Colin Percival Security Officer Emeritus, FreeBSD | The power to serve Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid
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