From owner-freebsd-hackers  Wed Dec 11 18:59:12 2002
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Date: Wed, 11 Dec 2002 18:59:09 -0800 (PST)
From: Matthew Dillon <dillon@apollo.backplane.com>
Message-Id: <200212120259.gBC2x97R092440@apollo.backplane.com>
To: John Baldwin <jhb@FreeBSD.ORG>
Cc: Chuck Tuffli <chuck_tuffli@agilent.com>,
	freebsd-hackers@FreeBSD.ORG
Subject: Re: RE: registers not saved
References:  <XFMail.20021210145733.jhb@FreeBSD.org>
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:> function A calls function B which uses ecx as a loop index. The bad part is function B never
:> saves/restores the value of ecx and function A starts dereferencing garbage.
:> 
:> An informal sampling of my driver seems to indicate that ebx gets
:> pushed/poped at entry/exit but ecx and edx don't. Does any of this
:> sound familiar? Thanks!
:
:Yes, eax, ebx, and edx are not "call-safe" registers.  If you are writing
:your own function in assembly and you call a function you need to either
:save those registers yourself or reload their values.  If you are writing
:...
:John Baldwin <jhb@FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
:"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

    I think you meant ecx there.  eax, ecx, and edx are not call safe.
    ebx is.

					-Matt


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