Re: RFC: A new MIPS64 ABI

[David Daney <ddaney at caviumnetworks dot com>]

On 02/14/2011 06:33 PM, Matt Thomas wrote:
> On Feb 14, 2011, at 6:22 PM, David Daney wrote:
>
> > On 02/14/2011 04:15 PM, Matt Thomas wrote:
> > > I have to wonder if it's worth the effort.  The primary problem I see
> > > is that this new ABI requires a 64bit kernel since faults through the
> > > upper 2G will go through the XTLB miss exception vector.
> >
> > Yes, that is correct.  It is a 64-bit ABI, and like the existing n32 ABI requires a 64-bit kernel.
>
> N32 doesn't require a LP64 kernel, just a 64-bit register aware kernel.
> Your N32-big does require a LP64 kernel.

But using 'official' kernel sources the only way to get a 64-bit 
register aware kernel is for it to also be LP64.  So effectively, you do 
in fact need a 64-bit kernel to run n32 userspace code.

My proposed ABI would need trivial kernel changes:

o Fix a couple of places where pointers are sign extended instead of 
zero extended.

o Change the stack address and address ranges returned by mmap().


The main work would be in the compiler toolchain and runtime libraries.


David Daney