[PATCH/RFC] Glibc Support for Thread Local Storage Descriptors in ARM platform

["Glauber de Oliveira Costa" <glommer at gmail dot com>]

Hello All,

Troughout the last months, Alexandre Oliva and I developed an ABI
extension to allow ARM binaries to benefit from his newly devised TLS
Descriptor method for accessing TLS variables
(http://www.lsd.ic.unicamp.br/~aoliva/writeups/TLS/paper-gcc2006.pdf).
Our proposed ABI can be found at
http://www.lsd.ic.unicamp.br/~aoliva/writeups/TLS/RFC-TLSDESC-ARM.txt
,  and a paper describing the ARM implementation, to be presented at
Linux Kongress in the first week of September at
http://www.lsd.ic.unicamp.br/~oliva/writeups/TLS/paper-lk2006.pdf. We
there describes some results we've got, that indicates a speedup of
more than 2 times for the most common case.

Attached to this message, follows 3 files that composes the patch to
enable TLS descriptors in the GNU libc. The patch is split for
simplicity, as follows:

libc-generic: contains some code that should be applied to the libc
generic tree, by anyone willing to test TLS descriptors. It is
basically the same code Oliva wrote for x86{,_64}, and it's already
being discussed for merging in the main tree.

elf-relocs: contains the relocations definitions. These numbers are
not guaranteed to be kept, as they're not yet aproved by the ARM EABI.

arm-tlsdesc: contains the specific code, for which I expect the most
comments from people in this list.

Any comments (in any part) is more than welcome.

--
"Free as in Freedom"
Glauber de Oliveira Costa.

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