From owner-freebsd-hackers Thu Apr 25 10:26:57 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mailhub.yumyumyum.org (dsl092-171-091.wdc1.dsl.speakeasy.net [66.92.171.91]) by hub.freebsd.org (Postfix) with SMTP id F24ED37B41D for ; Thu, 25 Apr 2002 10:26:47 -0700 (PDT) Received: (qmail 45290 invoked from network); 25 Apr 2002 17:26:16 -0000 Received: from dsl092-171-091.wdc1.dsl.speakeasy.net (66.92.171.91) by dsl092-171-091.wdc1.dsl.speakeasy.net with SMTP; 25 Apr 2002 17:26:16 -0000 Date: Thu, 25 Apr 2002 13:26:16 -0400 (EDT) From: Kenneth Culver To: Andrew Gallatin Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: pushal & ebp In-Reply-To: <15560.14613.989930.797068@grasshopper.cs.duke.edu> Message-ID: <20020425132419.A45267-100000@alpha.yumyumyum.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, 25 Apr 2002, Andrew Gallatin wrote: > > Kenneth Culver writes: > > > I just looked at the NetBSD code & like linux, they use a macro which > > > individually pushes the registers onto the stack rather than using > > > pushal (which I assume is the same as what intel calls PUSHAD in their > > > x86 instruction set ref. manual). > > > > > > NetBSD stopped using pushal in 1994 in rev 1.85 of their > > > arch/i386/i386/locore.s in a commit helpfully documented > > > "Don't use pusha and popa." > > > > > > Does anybody know why the other OSes push the registers individually, > > > rather than using pushal? Could our using pushal be causing Kenneth's > > > ebp to get lost, or is this just a red herring? > > > > > > Thanks, > > > > > > Drew > > > > > > > > > > > according to the intel docs, pushad (or what I'm assuming is pushal in our > > case) pushes eax, ecx, edx, ebx then pushes some temporary value (the > > original esp I think) then pushes ebp, esi, and edi: > > > > this is from the documentation for pushad > > > > IF OperandSize = 32 (* PUSHAD instruction *) > > THEN > > Temp (ESP); > > Push(EAX); > > Push(ECX); > > Push(EDX); > > Push(EBX); > > Push(Temp); > > Push(EBP); > > Push(ESI); > > Push(EDI); > > > > so could this be the problem? > > > > Ken > > I don't think so. The temp its pushing is the stack pointer. If you > look at the layout of the trap frame, then you'll see tf_isp comes > between tf_ebp & tf_ebx. I assume tf_isp is the stack pointer, so > that should be OK.. > > Drew > > > hrmm, well then it looks like pushal should be doing the right thing... but I thought though that esp was the stack pointer... it's pushing the original stack pointer onto isp, and then pushing ebp... I don't see why this would screw anything up... Ken To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message