segment register usage (was: Re: 386/486)

[Andreas Fuchs]

On 2003-07-23, Matthew Dillon <dillon at xxxxxxxxxxxxxxxxxxxx> wrote:
>     I am not particularly interested in continuing suppor for the 386,
>     not when competitor's cpus (like the VIA C3) are at a minimum
>     pentium compatible.  That said I see no particular reason to rip
>     386 support out for UP (though I don't even know if it still
>     works!  My %fs globaldata access code might have broken it!),
>     because it does not generally interfere with development.

Ah, that reminds me. Which segment registers can user applications
expect to be usable throughout DragonFlyBSD's development? I'm asking
because wine and multithreaded sbcl expect the %fs register to not get
clobbered, to store thread-local data there.

Also, will you remove the requirement to recompile the kernel with
option USER_LDT to get access to the i386_set/get_ldt functions? These
are really useful if you have a free segment register to point to an LDT
containing thread-local data.

Anyway, good luck getting DragonFlyBSD up; you all seem to be doing very
well. Best,
-- 
Andreas Fuchs, <asf at xxxxxxx>, asf at xxxxxxxxx, antifuchs