struct sysentvec field

[gerarra at tin.it]

Hi,
I've seen  void (*sv_prepsyscall)(struct trapframe *, int *, u_int *, caddr_t
*);  field in struct sysentvec defined in sys/sysent.h; I've seen it's call
be the current process in syscall interrupt 0x80 handling and it seems to
set number of arguments and base pointer for syscall arguments. It's not
a comment in the code, somebody could tell me what is the task of this field?

thanks

rookie