linux-kernel - [x86] fs, gs purpose & multicore prog

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Message-Id: <200809031109.45660.goretux@gmail.com>
Date:	Wed, 3 Sep 2008 11:09:45 +0200
From:	Eric Lacombe <tuxiko@...e.fr>
To:	linux-kernel@...r.kernel.org
Cc:	goretux@...il.com
Subject: [x86] fs, gs purpose & multicore prog

Hello,

I've some questions about IA-32e in Linux.

- What is the FS and GS segments role inside the kernel ?
(I was thinking about thread local storage)

- When I do a "mov %fs ..." instruction (in a module), it seems that %fs is 
equal to 0 (idem for %gs). Are these registers not always filled ?

- What is the purpose of MSR_FS_BASE and MSR_GS_BASE ? 
(I thought they were filled with "gdt[fs_entry].base")

- My last question is about the kernel programation of multi-core (or 
multiprocessor)
architecture. I don't see a lot of documentation about that on Internet.
Do you have some docs/urls about this topic.
Maybe someone can briefly explain how the execution flow are given to the 
different cores.

Thanks in advance.

        Eric
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