Date: Thu, 25 Apr 2002 13:13:53 -0400 (EDT) From: John Baldwin <jhb@FreeBSD.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-hackers@FreeBSD.ORG, Kenneth Culver <culverk@alpha.yumyumyum.org> Subject: Re: pushal & ebp Message-ID: <XFMail.20020425131353.jhb@FreeBSD.org> In-Reply-To: <15560.14613.989930.797068@grasshopper.cs.duke.edu>
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On 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.. Right. > Drew -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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