Date: Sun, 23 Dec 2001 13:09:39 -0500 From: Dan Eischen <eischen@vigrid.com> To: Doug Rabson <dfr@nlsystems.com> Cc: Bernd Walter <ticso@cicely9.cicely.de>, Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-alpha@FreeBSD.ORG Subject: Re: Munging jmp_bufs on alpha Message-ID: <3C261DE3.3EEFCEBB@vigrid.com> References: <20011223104757.B457-100000@salmon.nlsystems.com>
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Doug Rabson wrote:
>
> On Fri, 21 Dec 2001, Daniel Eischen wrote:
>
> > What is T12 suppose to contain in a normal function call? Is
> > it always the return address? Is that dependent on our compiler?
>
> T12 should be set to the address of the called function. Prologue code in
> the called function uses this assumption to initialise GP to the correct
> value for the module containing it. RA will be set to the return address
> by the call instruction itself.
OK, thanks. I think I understand this a little better.
I need to revisit my {get,set,make,swap}context patches, because
libc_r should really be using makecontext instead of having its
own MD macros to munge a jmp_buf. The alpha is a little tricky
though because a trapframe and sigframe are different formats,
and the *context routines would probably need to recognize the
difference. I think the kernel needs to get involved in order
to tag them appropriately.
--
Dan Eischen
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