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