From owner-freebsd-current@FreeBSD.ORG Tue Oct 18 16:26:37 2011 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C7F14106564A for ; Tue, 18 Oct 2011 16:26:37 +0000 (UTC) (envelope-from lacombar@gmail.com) Received: from mail-wy0-f182.google.com (mail-wy0-f182.google.com [74.125.82.182]) by mx1.freebsd.org (Postfix) with ESMTP id 599948FC19 for ; Tue, 18 Oct 2011 16:26:37 +0000 (UTC) Received: by wyi40 with SMTP id 40so998466wyi.13 for ; Tue, 18 Oct 2011 09:26:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=TTZiFGGP+PRfw92IXHX+BQtjG7A45XfLW1XN5X7bScs=; b=IBEeskxznMK50NgCO8QyPjLX+/fWTsJgAoC+IO9uqvQw5KkTRGCLcOlxgzioZeerKP wSFVUMWITfJ8FkFuevcx8V77qPL0xZDGNTAOL9ANUo2e6oGNT2B57LDGO3hg54BMlw9n 8w4X0cI1iNQ7SX3xzT5sd027GivDcgqmXRomk= MIME-Version: 1.0 Received: by 10.227.166.69 with SMTP id l5mr1081030wby.34.1318955196379; Tue, 18 Oct 2011 09:26:36 -0700 (PDT) Received: by 10.180.103.198 with HTTP; Tue, 18 Oct 2011 09:26:36 -0700 (PDT) In-Reply-To: References: <20111018090750.GG50300@deviant.kiev.zoral.com.ua> Date: Tue, 18 Oct 2011 12:26:36 -0400 Message-ID: From: Arnaud Lacombe To: Garrett Cooper Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: Kostik Belousov , current@freebsd.org, Oliver Pinter Subject: Re: [RFC] Enable nxstack by default X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 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: Tue, 18 Oct 2011 16:26:37 -0000 Hi, On Tue, Oct 18, 2011 at 11:44 AM, Garrett Cooper wrote= : > On Tue, 18 Oct 2011, Arnaud Lacombe wrote: > >> Hi, >> >> On Tue, Oct 18, 2011 at 5:07 AM, Kostik Belousov >> wrote: >>> >>> On Mon, Oct 17, 2011 at 09:30:56PM +0200, Oliver Pinter wrote: >>>> >>>> Hi all! >>>> >>>> I think, it's the time to enable the nxstack feature. Any comments, >>>> pros, cons? >>> >>> I dragged the change long enough for it to miss the 9.0. >>> After the 9.0 is released, I will flip the switch with the following >>> change. >>> >>> diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c >>> index 8455f48..926fe64 100644 >>> --- a/sys/kern/imgact_elf.c >>> +++ b/sys/kern/imgact_elf.c >>> @@ -118,7 +118,12 @@ static int elf_legacy_coredump =3D 0; >>> =A0SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, >>> =A0 =A0 &elf_legacy_coredump, 0, ""); >>> >>> -static int __elfN(nxstack) =3D 0; >>> +int __elfN(nxstack) =3D >>> +#if defined(__amd64__) || defined(__powerpc64__) /* both 64 and 32 bit >>> */ >>> >> Why leaving 32bits x86 CPU supporting the NX feature behind ? > > Most likely because it was assumed that i386 doesn't fully support it. > According to ye great Wikipedia, NX support didn't roll into i386 until > Prescott, which was pretty late in the non-64-bit capable family of CPUs,= as > its successor -- Conroe -- was 64-bit. Intel detuned some of the early Du= al > Core Pentiums, e.g. the Yonahs to not talk 64-bit. Not sure about AMD. > > There are probably more details in binutils, gcc, etc, that I'm missing a= nd > Kostik can expound on. > NX support is advertised in the cpuid flags, just add the logic to handle this interface. Kostik's patch is just incomplete, but he's got a commit bit so he can commit it as-is, as he will. If nonexec_stack becomes the default, it should be on every CPU supporting the feature, not just the low-hanging one. - Arnaud