Re: Re: NPTL/TLS "emulation" idea (fwd)

[David Hopwood <david.nospam.hopwood@blueyonder.co.uk>]

Jakub Jelinek wrote:
> On Wed, Oct 20, 2004 at 06:27:39PM +0100, Keir Fraser wrote:
>>>On Wed, Oct 20, 2004 at 12:55:22PM -0400, Rik van Riel wrote:
>>>
>>>>   4. Provide an alternative libc that does the +ve accesses (which are
>>>>      libc private, afaik) in another segment.  This does not break the
>>>>      ABI for userland programs and -ve accesses aren't that bad when
>>>>      there are no +ve accesses in the same segment.
>>>
>>>No, the ABI uses -ve accesses and %gs:0 (4 bytes there), +ve accesses
>>>above +4 are glibc private.
>>
>>Could we duplicate %gs:0 at %gs:-4 and update the ABI? Or is the ABI
>>now set in stone?
> 
> The ABI is there for several years, used e.g. in Solaris as well
> and is used already in several libraries, not just glibc.
> The ABI is not going to change for the sake of emulators.

This aspect of the TLS ABI has also been a problem for L4, although for
a different reason (they had already used %gs:0 for something else).
I can't immediately see any solutions arising from that discussion, but
in case it gives anyone else an idea, see
<http://lists.ira.uka.de/pipermail/l4ka/2004-March/000874.html>.

Looks like the same problem is also going to come up for the AMD64 port:
<http://lists.freebsd.org/pipermail/freebsd-threads/2004-March/001850.html>

-- 
David Hopwood <david.nospam.hopwood@blueyonder.co.uk>



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