On Wed, Jun 02, 2010 at 03:17:38PM +0500, adnan iqbal wrote:
> I am able to find system call list (o32 and n64) in
> /usr/include/asm/unistd.h over octeon/debian board. I am looking for details
> about these system calls so that for each system call i know exactly
> 1. What parmeters should be set in which registers before syscall
> 2. Which registers contain output of those system calls.
The basic concept for all ABIs is that syscalls are working almost like
subroutine calls, so:
o arguments are passed in $a0 - $a3 for o32
o arguments are passed in $a0 - $a7 for N32 and N64
o argument that don't fit into the argument registers are passed on the
o for details such as alignment of 64-bit arguments the usual ABI
o the result is return in $v0
In addition to normal subroutine calls:
o $a3 on syscall return will indicate success or error. 0 means success,
non-zero means an error happened in which case $v0 will contain an
errno.h error code.
o Many syscalls deviate from this convention. For example the sigreturn
family of syscalls doesn't return a result or error status.
o pipe() will return the 2nd filedescriptor of the result in $v1.
o vfork is even more weird.
o The ABI differences mean there are many subtle difference between the