sysdeps/unix/sysv/linux/powerpc/powerpc32/vfork.S

   1 /* Copyright (C) 2003-2014 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, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <sysdep.h>
  19 #define _ERRNO_H        1
  20 #include <bits/errno.h>
  21 #include <kernel-features.h>
  22 #include <tcb-offsets.h>
  23
  24 /* Clone the calling process, but without copying the whole address space.
  25    The calling process is suspended until the new process exits or is
  26    replaced by a call to `execve'.  Return -1 for errors, 0 to the new process,
  27    and the process ID of the new process to the old process.  */
  28
  29 ENTRY (__vfork)
  30
  31         /* Load the TCB-cached PID value and negates it. If It it is zero
  32            sets it to 0x800000.  And then sets its value again on TCB field.
  33            See raise.c for the logic that relies on this value.  */
  34
  35         lwz     r0,PID(r2)
  36         cmpwi   cr0,r0,0
  37         neg     r0,r0
  38         bne-    cr0,1f
  39         lis     r0,0x8000
  40 1:      stw     r0,PID(r2)
  41
  42         DO_CALL (SYS_ify (vfork))
  43
  44         cmpwi   cr1,r3,0
  45         beqlr-  1
  46
  47         /* Restore the original value of the TCB cache of the PID, if we're
  48            the parent.  But in the child (syscall return value equals zero),
  49            leave things as they are.  */
  50         lwz     r0,PID(r2)
  51         /* Cannot use clrlwi. here, because cr0 needs to be preserved
  52            until PSEUDO_RET.  */
  53         clrlwi  r4,r0,1
  54         cmpwi   cr1,r4,0
  55         beq-    cr1,1f
  56         neg     r4,r0
  57 1:      stw     r4,PID(r2)
  58
  59         PSEUDO_RET
  60
  61 PSEUDO_END (__vfork)
  62 libc_hidden_def (__vfork)
  63
  64 weak_alias (__vfork, vfork)
  65 strong_alias (__vfork, __libc_vfork)