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