problem about the tool chain for R3000

problem about the tool chain for R3000

[guo guo]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=GB2312, Size: 592 bytes --]

Dear All,

I'm trying to build tool chain with gcc4.2, binutils2.17 and glibc2.5
for mips r3000 chip.
During configure gcc I add ¨Cmabi=32 ¨Cmarch=r3000 ¨Cmtune=r3000. and
during building glibc, I add CFLAGS= -O2 ¨Cmabi=32 ¨Cmarch=r3000
¨Cmtune=r3000,
Then I dissembled the libc-2.5.90.so to check the instructions. I
found it has two instructions rdhwr(0x7c03e83b) and sync(0x0000000f)
that don't belongs to mips r3000.
I see some engineers use kernel to trap rdhwr but it may cost to more
resource.
Can it avoid there two instructions by special configuration or patch?

Best regards,
Tony

Re: problem about the tool chain for R3000

[David Daney]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=GB2312, Size: 956 bytes --]

guo guo wrote:
> Dear All,
> 
> I'm trying to build tool chain with gcc4.2, binutils2.17 and glibc2.5
> for mips r3000 chip.
> During configure gcc I add ¨Cmabi=32 ¨Cmarch=r3000 ¨Cmtune=r3000. and
> during building glibc, I add CFLAGS= -O2 ¨Cmabi=32 ¨Cmarch=r3000
> ¨Cmtune=r3000,
> Then I dissembled the libc-2.5.90.so to check the instructions. I
> found it has two instructions rdhwr(0x7c03e83b) and sync(0x0000000f)
> that don't belongs to mips r3000.

The rdhwr and sync are used by the NPTL pthread library and must be
emulated by the linux kernel.  Probably you will see ll and sc in there
as well.  If you use glibc2.3.x with Linux threads then the rdhwr will
not be generated.

 Probably if you did not use libpthread you would not need any of the
thread synchronization primitives that cause ll,sc, and sync to be
generated.

But if you want libpthread and your CPU does not support the
instructions, you will have to emulate them.


David Daney

Re: problem about the tool chain for R3000

[guo guo]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=GB2312, Size: 1379 bytes --]

Dear Daney,
Thank you very much.
Under nptl directory, there are 6 places use rdhwr instruction. What's
difference between rdhwr and move instructions?
Could I use move or other r3000 instructions to replace rdhwr?

And I didn't find ll/sc instructions in libc-2.5.90.so. maybe gcc
avoid them for R3000 chip.

Best regards,
Tony


2007/8/29, David Daney <ddaney@avtrex.com>:
> guo guo wrote:
> > Dear All,
> >
> > I'm trying to build tool chain with gcc4.2, binutils2.17 and glibc2.5
> > for mips r3000 chip.
> > During configure gcc I add ¨Cmabi=32 ¨Cmarch=r3000 ¨Cmtune=r3000. and
> > during building glibc, I add CFLAGS= -O2 ¨Cmabi=32 ¨Cmarch=r3000
> > ¨Cmtune=r3000,
> > Then I dissembled the libc-2.5.90.so to check the instructions. I
> > found it has two instructions rdhwr(0x7c03e83b) and sync(0x0000000f)
> > that don't belongs to mips r3000.
>
> The rdhwr and sync are used by the NPTL pthread library and must be
> emulated by the linux kernel.  Probably you will see ll and sc in there
> as well.  If you use glibc2.3.x with Linux threads then the rdhwr will
> not be generated.
>
>  Probably if you did not use libpthread you would not need any of the
> thread synchronization primitives that cause ll,sc, and sync to be
> generated.
>
> But if you want libpthread and your CPU does not support the
> instructions, you will have to emulate them.
>
>
> David Daney
>

Re: problem about the tool chain for R3000

[David Daney]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset=GB2312, Size: 1669 bytes --]

guo guo wrote:
> Dear Daney,
> Thank you very much.
> Under nptl directory, there are 6 places use rdhwr instruction. What's
> difference between rdhwr and move instructions?
> Could I use move or other r3000 instructions to replace rdhwr?

No.  The register that rdhwr is reading is not implemented on any
current processor.  It is always emulated by the kernel.  You cannot
remove it as it performs the critical function of loading the pointer to
the thread local area.

> 
> And I didn't find ll/sc instructions in libc-2.5.90.so. maybe gcc
> avoid them for R3000 chip.
> 
> Best regards,
> Tony
> 
> 
> 2007/8/29, David Daney <ddaney@avtrex.com>:
>> guo guo wrote:
>>> Dear All,
>>>
>>> I'm trying to build tool chain with gcc4.2, binutils2.17 and glibc2.5
>>> for mips r3000 chip.
>>> During configure gcc I add ¨Cmabi=32 ¨Cmarch=r3000 ¨Cmtune=r3000. and
>>> during building glibc, I add CFLAGS= -O2 ¨Cmabi=32 ¨Cmarch=r3000
>>> ¨Cmtune=r3000,
>>> Then I dissembled the libc-2.5.90.so to check the instructions. I
>>> found it has two instructions rdhwr(0x7c03e83b) and sync(0x0000000f)
>>> that don't belongs to mips r3000.
>> The rdhwr and sync are used by the NPTL pthread library and must be
>> emulated by the linux kernel.  Probably you will see ll and sc in there
>> as well.  If you use glibc2.3.x with Linux threads then the rdhwr will
>> not be generated.
>>
>>  Probably if you did not use libpthread you would not need any of the
>> thread synchronization primitives that cause ll,sc, and sync to be
>> generated.
>>
>> But if you want libpthread and your CPU does not support the
>> instructions, you will have to emulate them.
>>
>>
>> David Daney
>>