++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                           lib/syscall/_exit.s
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  0  .sect .text
  1  .extern ___exit
  2  .define __exit
  3  .align 2
    
  4  __exit:
  5          jmp     ___exit
       
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                           lib/posix/__exit.c
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
110  #define _exit   __exit
111  #include <lib.h>
112  #include <unistd.h>
       
113  PUBLIC void _exit(status)
114  int status;
115  {
116    message m;
       
117    m.m1_i1 = status;
118    _syscall(MM, EXIT, &m);
119  }

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                          lib/other/syscall.s
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
200  #include <lib.h>

201  PUBLIC int _syscall(who, syscallnr, msgptr)
202  int who;
203  int syscallnr;
204  register message *msgptr;
205  {
206    int status;

207    msgptr->m_type = syscallnr;
208    status = _sendrec(who, msgptr);
209    if (status != 0) {
210          /* 'sendrec' itself failed. */
211          /* XXX - strerror doesn't know all the codes */
212          msgptr->m_type = status;
213    }
214    if (msgptr->m_type < 0) {
215          errno = -msgptr->m_type;
216          return(-1);
217    }
218    return(msgptr->m_type);
219  }

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                      lib/i386/rts/_sendrec.s
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
300  .sect .text; .sect .rom; .sect .data; .sect .bss
301  .define __send, __receive, __sendrec

302  ! See ../h/com.h for C definitions
303  SEND = 1
304  RECEIVE = 2
305  BOTH = 3
306  SYSVEC = 33

307  SRCDEST = 8
308  MESSAGE = 12

309  !*========================================================================*
310  !                           _send and _receive                            *
311  !*========================================================================*
312  ! _send(), _receive(), _sendrec() all save ebp, but destroy eax and ecx.
313  .define __send, __receive, __sendrec
314  .sect .text
315  __send:
316      push    ebp
317      mov ebp, esp
318      push    ebx
319      mov eax, SRCDEST(ebp)   ! eax = dest-src
320      mov ebx, MESSAGE(ebp)   ! ebx = message pointer
321      mov ecx, SEND           ! _send(dest, ptr)
322      int SYSVEC              ! trap to the kernel
323      pop ebx
324      pop ebp
325      ret

326  __receive:
327      push    ebp
328      mov ebp, esp
329      push    ebx
330      mov eax, SRCDEST(ebp)   ! eax = dest-src
331      mov ebx, MESSAGE(ebp)   ! ebx = message pointer
332      mov ecx, RECEIVE        ! _receive(src, ptr)
333      int SYSVEC              ! trap to the kernel
334      pop ebx
335      pop ebp
336      ret

337  __sendrec:
338      push    ebp
339      mov ebp, esp
340      push    ebx
341      mov eax, SRCDEST(ebp)   ! eax = dest-src
342      mov ebx, MESSAGE(ebp)   ! ebx = message pointer
343      mov ecx, BOTH           ! _sendrec(srcdest, ptr)
344      int SYSVEC              ! trap to the kernel
345      pop ebx
346      pop ebp
347      ret