Date: Sat, 17 Aug 2002 12:06:32 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Ian Dowse <iedowse@maths.tcd.ie> Cc: arch@FreeBSD.ORG Subject: Re: Solving the stack gap issue Message-ID: <200208171906.g7HJ6WiA068153@apollo.backplane.com> References: <200208171918.aa72556@salmon.maths.tcd.ie>
next in thread | previous in thread | raw e-mail | index | archive | help
:A few approaches have been suggested:
:- Lock access to the stack gap, so that only one thread at a time
: can use it.
:- Use a different address region for each thread.
:- Avoid the need for the stack gap by providing kernel-callable versions
: of all syscalls.
:
:...
:I have attempted to implement the third approach. It requires more
:extensive changes than the others, but it has the advantage of
:aiming to remove the stack gap hack instead of just adding another
:bad-aid to it. That said, it does add some overhead to normal system
:calls, so it may be that some ugliness is necessary to balance this
:tradeoff.
Good god! Ian, you've done the grunge work that nobody else wanted
to do! This is great! It will also make the ABI work discussed a few
months ago far easier to accomplish.
I believe that your patch and approach is not only convenient, it is
a necessary prerequisit for current and future ABI work in -current.
I think you should commit it as soon as you think it's safe. Is there
any specific kind of testing you would like done?
Now that I have the TCP stuff comitted, the next thing on my agenda
is the 64 bit ABI. Your work simplifies my task enormously. For
example it allows me to make sys_*() functions take 64 bit arguments
natively where appropriate and make the 32 bit syscalls convert.
-Matt
Matthew Dillon
<dillon@backplane.com>
:Anyway, there's a patch against -current at:
:
: http://www.maths.tcd.ie/~iedowse/FreeBSD/stackgap.diff
:
:This removes 80-90% of the stack gap uses in the i386 Linux emulation
:code. I haven't done more than a basic level of testing though. I'm
:also not particularly attached to any of the approaches taken here
:- it is really just a proof of concept for this approach. Any
:comments welcome!
:
:Ian
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200208171906.g7HJ6WiA068153>