Re: pa-risc/linux abi

[Randolph Chung <tausq@debian.org>]

> > Can you confirm that Linux uses HP's 32 bit ABI (i.e., which registers
> > are used in argument passing, and how the stack frame works)?  My
> 
> Debian hppa is 32 bit -- will forward the rest of this to the experts.
> 
> > assembly kernel works under HP-UX, and I'm wondering if it will under
> > linux.  The document I used to write it I found on the linux site, but
> > it's an HP doc:
> >    http://ftp.parisc-linux.org/docs/arch/rad_11_0_32.pdf

I wrote some comments for the 32-bit calling convention (64-bit is
somewhat similar) for libffi. 

http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/libffi/src/pa/ffi.c?rev=1.1&content-type=text/x-cvsweb-markup


/* PA has a downward growing stack, which looks like this:
  
   Offset
        [ Variable args ]
   SP = (4*(n+9))       arg word N
   ...
   SP-52                arg word 4
        [ Fixed args ]
   SP-48                arg word 3
   SP-44                arg word 2
   SP-40                arg word 1
   SP-36                arg word 0
        [ Frame marker ]
   ...
   SP-20                RP
   SP-4                 previous SP
  
   First 4 non-FP 32-bit args are passed in gr26, gr25, gr24 and gr23
   First 2 non-FP 64-bit args are passed in register pairs, starting
     on an even numbered register (i.e. r26/r25 and r24+r23)
   First 4 FP 32-bit arguments are passed in fr4L, fr5L, fr6L and fr7L
   First 2 FP 64-bit arguments are passed in fr5 and fr7
   The rest are passed on the stack starting at SP-52, but 64-bit
     arguments need to be aligned to an 8-byte boundary
  
   This means we can have holes either in the register allocation,
   or in the stack.  */

randolph
-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/