Basic ABI: SysV i386

Out-of-Process Method Invocation:
   Caller:
      eax: reserved, must be zero
      edx: pointer to parameter info block (PIB)
      ecx: maximum "out" bytes, excluding Inlines

      Call the 32-bit address stored at 0x7fff0000 to invoke the method.
      
      Upon return:
      ebx, esi, edi, ebp, esp: preserved
      eax: pointer to exception, or NULL if none.
           If there is an exception, the user part of the syscall
           function will search for an exception handling function
           that covers the calling address.  If none is found,
           it will assume that it is a language without exception
           handling, and return the exception to the caller in eax.
      ecx: clobbered
      edx: pointer to args, with out params filled in; in params
           may be clobbered.  This will be the same pointer as
           was passed in by the caller.
      
   Callee:
      eax: pointer to PIB
      edx: pointer to caller information struct, if such was
           requested
      ecx: return address
      
      Upon return:
      
      eax: pointer to exception, or NULL if none.
      ebx, esi, edi, ebp, esp: should be preserved
      ecx, edx: may be clobbered