vfork.s

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* Copyright (C) 1999, 2000 Free Software Foundation, Inc.
   Copyright (C) 2001 Hewlett-Packard Australia

 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU Library General Public License as published by the Free
 Software Foundation; either version 2 of the License, or (at your option) any
 later version.

 This program is distributed in the hope that it will be useful, but WITHOUT
 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more
 details.

 You should have received a copy of the GNU Library General Public License
 along with this program; if not, write to the Free Software Foundation, Inc.,
 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

 Derived in part from the Linux-8086 C library, the GNU C Library, and several
 other sundry sources.  Files within this library are copyright by their
 respective copyright holders.
*/

#include <features.h>
#define _SYSCALL_H
#include <bits/sysnum.h>
#define _ERRNO_H	1
#include <bits/errno.h>

/* Clone the calling process, but without copying the whole address space.
   The calling process is suspended until the new process exits or is
   replaced by a call to `execve'.  Return -1 for errors, 0 to the new process,
   and the process ID of the new process to the old process.  */

.text
.align 4
.type	__vfork,@function
.globl	__vfork;
__vfork:
	mov.w	.L2, r3
	trapa	#0x10
	mov     r0, r1
#ifdef __sh2__
// 12 arithmetic shifts for the crappy sh2, because shad doesn't exist!	
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
#else		
	mov	#-12, r2
	shad	r2, r1
#endif

	not	r1, r1			// r1=0 means r0 = -1 to -4095
	tst	r1, r1			// i.e. error in linux
	bf	2f
	mov.w	.L1, r1
	cmp/eq	r1, r0
	bf/s	__syscall_error
	 mov	r0, r4

	/* If we don't have vfork, use fork.  */
	mov.w	.L3, r3
	trapa	#0x10
	mov     r0, r1
#ifdef __sh2__
// 12 arithmetic shifts for the crappy sh2, because shad doesn't exist!	
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
	shar	r1
#else		
	mov	#-12, r2
	shad	r2, r1
#endif

	not	r1, r1			// r1=0 means r0 = -1 to -4095
	tst	r1, r1			// i.e. error in linux
	bt/s	__syscall_error
	 mov	r0, r4
2:
	rts
	 nop

	.align	2
.L1:
	.word	-ENOSYS
.L2:
	.word	__NR_vfork
.L3:
	.word	__NR_fork
        .size   __vfork, .-__vfork
.weak	vfork
	vfork =  __vfork

#include "syscall_error.S"