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Re: thread-ready ABIs

To: Ulrich Drepper <drepper@redhat.com>
Subject: Re: thread-ready ABIs
From: Ralf Baechle <ralf@oss.sgi.com>
Date: Sat, 19 Jan 2002 16:14:05 -0800
Cc: "H . J . Lu" <hjl@lucon.org>, GNU libc hacker <libc-hacker@sources.redhat.com>, linux-mips@oss.sgi.com
In-reply-to: <m3elkn4ikq.fsf@myware.mynet>; from drepper@redhat.com on Fri, Jan 18, 2002 at 10:31:17AM -0800
References: <m3elkoa5dw.fsf@myware.mynet> <20020118101908.C23887@lucon.org> <m3elkn4ikq.fsf@myware.mynet>
Sender: owner-linux-mips@oss.sgi.com
User-agent: Mutt/1.2.5i
On Fri, Jan 18, 2002 at 10:31:17AM -0800, Ulrich Drepper wrote:

> > I don't see there are any registers we can use without breaking ABI.
> > On the other hand, can we change the mips kernel to save k0 or k1 for
> > user space?

These are reserved for kernel use.  Saving them is not a good idea as it
would impact performance of TLB exception handlers which are extremly
performance sensitive.

> Are these registers which are readable by normal users but writable
> only in ring 0?  If yes, this is definitely worthwhile (similar to how
> x86 works).  The only problem will be the MIPS variants which don't
> have this register.  I bet there are some.

No.

  Ralf

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