1/*
2    SDL - Simple DirectMedia Layer
3    Copyright (C) 1997-2012 Sam Lantinga
4
5    This library is free software; you can redistribute it and/or
6    modify it under the terms of the GNU Lesser General Public
7    License as published by the Free Software Foundation; either
8    version 2.1 of the License, or (at your option) any later version.
9
10    This 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    Lesser General Public License for more details.
14
15    You should have received a copy of the GNU Lesser General Public
16    License along with this library; if not, write to the Free Software
17    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
18
19    Sam Lantinga
20    slouken@libsdl.org
21*/
22#include "SDL_config.h"
23
24#ifndef _ATARI_SUPER_h
25#define _ATARI_SUPER_h
26
27#include "SDL_stdinc.h"
28
29#ifndef SuperToUser
30
31/*
32 * Safe binding to switch back from supervisor to user mode.
33 * On TOS or EmuTOS, if the stack pointer has changed between Super(0)
34 * and Super(oldssp), the resulting user stack pointer is wrong.
35 * This bug does not occur with FreeMiNT.
36 * So the safe way to return from supervisor to user mode is to backup
37 * the stack pointer then restore it after the trap.
38 * Sometimes, GCC optimizes the stack usage, so this matters.
39 */
40#define SuperToUser(ptr)						\
41(void)__extension__							\
42({									\
43	register long retvalue __asm__("d0");				\
44	register long sp_backup;					\
45									\
46	__asm__ volatile						\
47	(								\
48		"movl	sp,%1\n\t"					\
49		"movl	%2,sp@-\n\t"					\
50		"movw	#0x20,sp@-\n\t"					\
51		"trap	#1\n\t"						\
52		"movl	%1,sp\n\t"					\
53	: "=r"(retvalue), "=&r"(sp_backup)	/* outputs */		\
54	: "g"((long)(ptr)) 			/* inputs */		\
55	: "d1", "d2", "a0", "a1", "a2"		\
56	);								\
57})
58
59#endif /* SuperToUser */
60
61#endif /* _ATARI_SUPER_h */
62