MIPS Thread Local Storage Help Request

[Joel Sherrill]

On 4/28/2014 1:56 PM, Gedare Bloom wrote:
> On Mon, Apr 28, 2014 at 2:47 PM, Joel Sherrill
> <joel.sherrill at oarcorp.com> wrote:
>> Hi
>>
>> This is going to be interesting. MIPS TLS is broken because
>> we don't have a trap handler for this. From GCC:
>>
>> ;; Thread-Local Storage
>>
>> ;; The TLS base pointer is accessed via "rdhwr $3, $29".  No current
>> ;; MIPS architecture defines this register, and no current
>> ;; implementation provides it; instead, any OS which supports TLS is
>> ;; expected to trap and emulate this instruction.  rdhwr is part of the
>> ;; MIPS 32r2 specification, but we use it on any architecture because
>> ;; we expect it to be emulated.  Use .set to force the assembler to
>> ;; accept it.
>> ;;
>> ;; We do not use a constraint to force the destination to be $3
>> ;; because $3 can appear explicitly as a function return value.
>> ;; If we leave the use of $3 implicit in the constraints until
>> ;; reload, we may end up making a $3 return value live across
>> ;; the instruction, leading to a spill failure when reloading it.
>>
>> This code from NetBSD appears to be the core part of the
>> handler.
>>
>> http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/mips/mips/locore_mips3.S?only_with_tag=MAIN
>>
> Do you mean
> http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/arch/mips/mips/mips_emul.c?rev=1.26&content-type=text/x-cvsweb-markup&only_with_tag=MAIN
> near case OP_RDHWR
>
Yeah.

And at one point I thought we had code similar to that because
the R3000 like the MongooseV needed help to be IEEE FP compliant.
And we used the NetBSD instruction trap emulator to help.
>> If someone can adapt this, then the MIPS will have working
>> TLS.
>>
>> Thanks.
>>
>> --
>> Joel Sherrill, Ph.D.             Director of Research & Development
>> joel.sherrill at OARcorp.com        On-Line Applications Research
>> Ask me about RTEMS: a free RTOS  Huntsville AL 35805
>> Support Available                (256) 722-9985
>>
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-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
Support Available                (256) 722-9985