/* Create new context.

   Copyright (C) 2012-2018 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, see

   <http://www.gnu.org/licenses/>.  */

#include <sysdep.h>

#include "ucontext_i.h"

ENTRY(__makecontext)

	move.l	4(%sp), %a0

	/* Get the address of the function we are supposed to run.  */

	move.l	8(%sp), oPC(%a0)

	/* Compute the address of the stack.  The information comes from

	   to us_stack element.  */

	move.l	oSS_SP(%a0), %a1

	add.l	oSS_SIZE(%a0), %a1

	/* Remember the number of parameters for the exit handler since

	   it has to remove them.  We store the number in the D7 register

	   which the function we will call must preserve.  */

	move.l	12(%sp), %d1

	move.l	%d1, oGREGS+7*4(%a0)

	/* Make room on the new stack for the parameters.

	   Room for the arguments, return address (== 1f) and

	   oLINK pointer is needed.  */

	neg.l	%d1

	lea	-8(%a1,%d1.l*4), %a1

	neg.l	%d1

	/* Store the future stack pointer.  */

	move.l	%a1, oSP(%a0)

	/* Put the next context on the new stack (from the uc_link

	   element).  */

	move.l	oLINK(%a0), 4(%a1,%d1.l*4)

	/* Copy all the parameters.  */

1:	subq.l	#1,%d1

	jmi	2f

	move.l	16(%sp,%d1.l*4), 4(%a1,%d1.l*4)

	jra	1b

2:

	/* If the function we call returns we must continue with the

	   context which is given in the uc_link element.  To do this

	   set the return address for the function the user provides

	   to a little bit of helper code which does the magic (see

	   below).  */

	lea	1f(%pc), %a0

	move.l	%a0, (%a1)

	/* 'makecontext' returns no value.  */

	rts

	/* This is the helper code which gets called if a function which

	   is registered with 'makecontext' returns.  In this case we

	   have to install the context listed in the uc_link element of

	   the context 'makecontext' manipulated at the time of the

	   'makecontext' call.  If the pointer is NULL the process must

	   terminate.

	   Make sure to separate the return label from the previous unwind

	   region, because the unwinder uses ra-1 to find the FDE.  */

	cfi_endproc

	nop

1:

	/* This removes the parameters passed to the function given to

	   'makecontext' from the stack.  D7 contains the number of

	   parameters (see above).  */

	lea	(%sp,%d7.l*4), %sp

	tst.l	(%sp)			/* Check the next context.  */

	jeq	2f			/* If it is zero exit.  */

	jbsr	JUMPTARGET(__setcontext)

	/* If this returns (which can happen if the syscall fails) we'll

	   exit the program with the return error value (-1).  */

	move.l	%d0, (%sp)

2:	jbsr	HIDDEN_JUMPTARGET(exit)

	/* The 'exit' call should never return.  In case it does cause

	   the process to terminate.  */

	illegal

	cfi_startproc

END(__makecontext)

weak_alias (__makecontext, makecontext)