sysdeps/unix/bsd/bsd4.4/kfreebsd/i386/vfork.S

   1 /* Copyright (C) 1999, 2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <sysdep.h>
  20
  21 /* Clone the calling process, but without copying the whole address space.
  22    The calling process is suspended until the new process exits or is
  23    replaced by a call to `execve'.  Return -1 for errors, 0 to the new process,
  24    and the process ID of the new process to the old process.  */
  25
  26 ENTRY (__vfork)
  27
  28         /* Pop the return PC value into ECX.  */
  29         popl    %ecx
  30         cfi_adjust_cfa_offset(-4)
  31         cfi_register (%eip, %ecx)
  32
  33         /* Perform the system call.  */
  34         DO_CALL (vfork, 0)
  35         jb      L(error)        /* Branch forward if it failed.  */
  36
  37         /* In the parent process, %edx == 0, %eax == child pid.  */
  38         /* In the child process, %edx == 1, %eax == parent pid.  */
  39
  40         /* Change %eax to be 0 in the child process.  */
  41         decl    %edx
  42         andl    %edx, %eax
  43
  44         /* Jump to the return PC.  */
  45         jmp     *%ecx
  46
  47 L(error):
  48         /* Push back the return PC.  */
  49         pushl   %ecx
  50         cfi_adjust_cfa_offset(4)
  51
  52         /* Branch to the error handler, hidden in PSEUDO_END.  */
  53         jmp     SYSCALL_ERROR_LABEL
  54 L(pseudo_end):
  55         ret
  56 PSEUDO_END (__vfork)
  57 libc_hidden_def (__vfork)
  58
  59 weak_alias (__vfork, vfork)