1/* SPDX-License-Identifier: GPL-2.0 */ 2#ifndef _M68K_SWITCH_TO_H 3#define _M68K_SWITCH_TO_H 4 5/* 6 * switch_to(n) should switch tasks to task ptr, first checking that 7 * ptr isn't the current task, in which case it does nothing. This 8 * also clears the TS-flag if the task we switched to has used the 9 * math co-processor latest. 10 */ 11/* 12 * switch_to() saves the extra registers, that are not saved 13 * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and 14 * a0-a1. Some of these are used by schedule() and its predecessors 15 * and so we might get see unexpected behaviors when a task returns 16 * with unexpected register values. 17 * 18 * syscall stores these registers itself and none of them are used 19 * by syscall after the function in the syscall has been called. 20 * 21 * Beware that resume now expects *next to be in d1 and the offset of 22 * tss to be in a1. This saves a few instructions as we no longer have 23 * to push them onto the stack and read them back right after. 24 * 25 * 02/17/96 - Jes Sorensen (jds@kom.auc.dk) 26 * 27 * Changed 96/09/19 by Andreas Schwab 28 * pass prev in a0, next in a1 29 */ 30asmlinkage void resume(void); 31#define switch_to(prev,next,last) do { \ 32 register void *_prev __asm__ ("a0") = (prev); \ 33 register void *_next __asm__ ("a1") = (next); \ 34 register void *_last __asm__ ("d1"); \ 35 __asm__ __volatile__("jbsr resume" \ 36 : "=a" (_prev), "=a" (_next), "=d" (_last) \ 37 : "0" (_prev), "1" (_next) \ 38 : "d0", "d2", "d3", "d4", "d5"); \ 39 (last) = _last; \ 40} while (0) 41 42#endif /* _M68K_SWITCH_TO_H */ 43