compilers/linux86-0.16.17/libc/crt0.c

   1 /* Copyright (C) 1995,1996 Robert de Bath <rdebath@cix.compulink.co.uk>
   2  * This file is part of the Linux-8086 C library and is distributed
   3  * under the GNU Library General Public License.
   4  */
   5
   6 #if defined(__AS386_16__) || defined(__AS386_32__)
   7 #define CRT0_OK
   8 /*
   9  * Change of aim here, to allow easy alteration for generation of COM files
  10  * this code has been moved into libc. This means only the linker needs to
  11  * to be told to fetch a different libc the crt0 is unaltered.
  12  *
  13  * This also allows us to deal with __FIRST_ARG_IN_AX__ and __CALLER_SAVES__
  14  * in the same way.
  15  */
  16
  17 #asm
  18 .text
  19 entry startup           ! Crt0 startup
  20 startup:
  21   br    ___cstartup
  22 export no_op
  23 no_op:                  ! Generic no operation call
  24   ret
  25
  26   .ascii __LIBC_VER__   ! Version id.
  27
  28   loc   1               ! Segment 1 is where the pointers to the autostart
  29                         ! functions are stored.
  30 #if !__AS386_32__
  31 ZP_safety:
  32   .word 0               ! But first some zeros to avoid null pointer writes.
  33   .word 0
  34   .word 0
  35   .word 0
  36 #endif
  37 export auto_start
  38 auto_start:
  39
  40 #endasm
  41 #endif /* __AS386_16__ or __AS386_32__ */
  42
  43 #if defined(__GNUC__) && defined(__i386__)
  44 #ifdef __ELF__
  45 #define CRT0_OK
  46 __asm__(".globl _start\n_start:");
  47 __asm__("jmp    __cstartup");
  48 __asm__(".globl __no_op\n__no_op:");
  49 __asm__("ret");
  50 #else
  51
  52 #error This library is for ELF only, sorry.
  53 __asm__(".globl startup\nstartup:");
  54 __asm__("jmp    ___cstartup");
  55 __asm__(".globl no_op\nno_op:");
  56 __asm__("ret");
  57 #endif
  58
  59 #endif /* defined(__GNUC__) && defined(__i386__) */
  60
  61 #ifndef CRT0_OK
  62 #error You are not going to get far without crt0.o!
  63 #endif