From owner-freebsd-current  Fri May 31 18: 0:19 2002
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Date: Fri, 31 May 2002 17:49:59 -0700 (PDT)
From: Julian Elischer <julian@elischer.org>
To: Jake Burkholder <jake@locore.ca>
Cc: FreeBSD current users <current@FreeBSD.ORG>
Subject: Re: Seeking OK to commit KSE MIII-again
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X-Loop: FreeBSD.ORG

interesting but not exactly brief.. :-)


On Fri, 31 May 2002, Jake Burkholder wrote:

> 
> The system call stubs in libc are leaf functions; basically just a
> trap instruction followed by a return.  They do not touch the stack
> at all, or change the stack pointer.  One of the first few instructions
> on entry to the kernel is a save, which rotates the register window
> and logically saves the call-safe registers onto the user stack
> (the outs become the ins, and the kernel gets new ins and locals,
> with the old ones being saved to the user stack once a flush is
> performed or they get spilled out).

the question is "when does it switch to the kernel stack?"
(and back?)


> 
> Here is a reference:  http://www.sparc.com/standards/v9.ps.Z

downloaded... 300+ pages.. hmm.


> 
> Jake
> 


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