sysdeps/unix/sysv/linux/aarch64/vfork.S

   1 /* Copyright (C) 1999-2014 Free Software Foundation, Inc.
   2
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public License as
   7    published by the Free Software Foundation; either version 2.1 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sysdep.h>
  20 #define _ERRNO_H        1
  21 #include <bits/errno.h>
  22
  23 /* Clone the calling process, but without copying the whole address space.
  24    The calling process is suspended until the new process exits or is
  25    replaced by a call to `execve'.  Return -1 for errors, 0 to the new process,
  26    and the process ID of the new process to the old process.  */
  27
  28 ENTRY (__vfork)
  29
  30         /* Save the TCB-cached PID away in w3, and then negate the TCB
  31            field.  But if it's zero, set it to 0x80000000 instead.  See
  32            raise.c for the logic that relies on this value.  */
  33         mrs     x2, tpidr_el0
  34         sub     x2, x2, #PTHREAD_SIZEOF
  35         ldr     w3, [x2, #PTHREAD_PID_OFFSET]
  36         mov     w1, #0x80000000
  37         negs    w0, w3
  38         csel    w0, w1, w0, eq
  39         str     w0, [x2, #PTHREAD_PID_OFFSET]
  40
  41         mov     x0, #0x4111     /* CLONE_VM | CLONE_VFORK | SIGCHLD */
  42         mov     x1, sp
  43         DO_CALL (clone, 2)
  44
  45         /* Restore the original value of the TCB cache of the PID, if we're
  46            the parent.  But in the child (syscall return value equals zero),
  47            leave things as they are.  */
  48         cbz     x0, 1f
  49         str     w3, [x2, #PTHREAD_PID_OFFSET]
  50 1:
  51         cmn     x0, #4095
  52         b.cs    .Lsyscall_error
  53         RET
  54
  55 PSEUDO_END (__vfork)
  56 libc_hidden_def (__vfork)
  57
  58 weak_alias (__vfork, vfork)
  59 strong_alias (__vfork, __libc_vfork)