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 stack. o for details such as alignment of 64-bit arguments the usual ABI conventions apply 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 syscall handlers. Ralf
