> > 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/
