glibc/sysdeps/unix/sysv/linux/x86_64/clone.S

/* Copyright (C) 2001,02 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; 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>
#include <asm-syntax.h>
#include <bp-sym.h>
#include <bp-asm.h>

/* The userland implementation is:
   int clone (int (*fn)(void *arg), void *child_stack, int flags, void *arg),
   the kernel entry is:
   int clone (long flags, void *child_stack).

   The parameters are passed in register from userland:
   rdi: fn
   rsi: child_stack
   rdx:	flags
   rcx: arg

   The kernel expects:
   rax: system call number
   rdi: flags
   rsi: child_stack  */


        .text
ENTRY (BP_SYM (__clone))
	/* Sanity check arguments.  */
	movq	$-EINVAL,%rax
	testq	%rdi,%rdi		/* no NULL function pointers */
	jz	SYSCALL_ERROR_LABEL
	testq	%rsi,%rsi		/* no NULL stack pointers */
	jz	SYSCALL_ERROR_LABEL

	/* Insert the argument onto the new stack.  */
	subq	$16,%rsi
	movq	%rcx,8(%rsi)

	/* Save the function pointer.  It will be popped off in the
	child in the ebx frobbing below.  */
	movq	%rdi,0(%rsi)

	/* Do the system call.  */
	movq	%rdx, %rdi
	movq	$SYS_ify(clone),%rax
	syscall

	testq	%rax,%rax
	jl	SYSCALL_ERROR_LABEL
	jz	thread_start

L(pseudo_end):
	ret

thread_start:
	/* Set up arguments for the function call.  */
	popq	%rax		/* Function to call.  */
	popq	%rdi		/* Argument.  */
	call	*%rax
	/* Call exit with return value from function call. */
	movq	%rax, %rdi
	call	HIDDEN_JUMPTARGET (_exit)

PSEUDO_END (BP_SYM (__clone))

weak_alias (BP_SYM (__clone), BP_SYM (clone))