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 */
30 asmlinkage 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 */