glibc/sysdeps/unix/sysv/linux/arm/clone.S

/* Copyright (C) 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Pat Beirne <patb@corelcomputer.com>

   The GNU C Library 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.

   The GNU C Library 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 the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

/* clone() is even more special than fork() as it mucks with stacks
   and invokes a function in the right context after its all over.  */

#include <sysdep.h>
#define _ERRNO_H	1
#include <bits/errno.h>

/* int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg); */

        .text
ENTRY(__clone)
	@ sanity check args
	cmp	r0, #0
	cmpne	r1, #0
	moveq	r0, #-EINVAL
	beq	PLTJMP(syscall_error)

	@ insert the args onto the new stack
	sub	r1, r1, #8
	str	r3, [r1, #4]
	@ save the function pointer as the 0th element
	str	r0, [r1]

	@ do the system call
	@ get flags 
	mov	r0, r2
	@ new sp is already in r1
	swi	SYS_ify(clone)
	cmn	a1, $4096
	bhs	PLTJMP(C_SYMBOL_NAME(__syscall_error))
	RETINSTR(movne,pc,lr)

	@ pick the function arg and call address off the stack and execute
	ldr	r0, [sp, #4]
	mov	lr, pc
	ldr 	pc, [sp]

	@ and we are done, passing the return value through r0
	b	PLTJMP(_exit)

PSEUDO_END (__clone)

weak_alias (__clone, clone)