Date: Thu, 25 Apr 2002 12:22:55 -0400 (EDT) From: Kenneth Culver <culverk@alpha.yumyumyum.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: Peter Wemm <peter@wemm.org>, John Baldwin <jhb@FreeBSD.ORG>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: pushal & ebp Message-ID: <20020425115941.C44727-100000@alpha.yumyumyum.org> In-Reply-To: <15560.4334.821343.177003@grasshopper.cs.duke.edu>
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> 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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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