sysdeps/unix/sysv/linux/i386/clone.S

   1 /* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Richard Henderson (rth@tamu.edu)
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 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    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 /* clone() is even more special than fork() as it mucks with stacks
  21    and invokes a function in the right context after its all over.  */
  22
  23 #include <sysdep.h>
  24 #define _ERRNO_H        1
  25 #include <bits/errno.h>
  26 #include <asm-syntax.h>
  27
  28 /* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg); */
  29
  30         .text
  31 ENTRY(__clone)
  32         /* Sanity check arguments.  */
  33         movl    $-EINVAL,%eax
  34         movl    4(%esp),%ecx            /* no NULL function pointers */
  35         testl   %ecx,%ecx
  36         jz      syscall_error
  37         movl    8(%esp),%ecx            /* no NULL stack pointers */
  38         testl   %ecx,%ecx
  39         jz      syscall_error
  40
  41         /* Insert the argument onto the new stack.  */
  42         subl    $8,%ecx
  43         movl    16(%esp),%eax           /* no negative argument counts */
  44         movl    %eax,4(%ecx)
  45
  46         /* Save the function pointer as the zeroth argument.
  47            It will be popped off in the child in the ebx frobbing below.  */
  48         movl    4(%esp),%eax
  49         movl    %eax,0(%ecx)
  50
  51         /* Do the system call */
  52         pushl   %ebx
  53         movl    16(%esp),%ebx
  54         movl    $SYS_ify(clone),%eax
  55         int     $0x80
  56         popl    %ebx
  57
  58         test    %eax,%eax
  59         jl      syscall_error
  60         jz      thread_start
  61
  62         ret
  63
  64 thread_start:
  65         subl    %ebp,%ebp       /* terminate the stack frame */
  66         call    *%ebx
  67 #ifdef PIC
  68         call    L(here)
  69 L(here):
  70         popl    %ebx
  71         addl    $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ebx
  72 #endif
  73         pushl   %eax
  74         call    JUMPTARGET (_exit)
  75
  76 PSEUDO_END (__clone)
  77
  78 weak_alias (__clone, clone)