1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _H8300_SWITCH_TO_H
3 #define _H8300_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, offset of tss in d1, and whether
29 * the mm structures are shared in d2 (to avoid atc flushing).
30 *
31 * H8/300 Porting 2002/09/04 Yoshinori Sato
32 */
33
34 asmlinkage void resume(void);
35 #define switch_to(prev, next, last) \
36 do { \
37 void *_last; \
38 __asm__ __volatile__( \
39 "mov.l %1, er0\n\t" \
40 "mov.l %2, er1\n\t" \
41 "mov.l %3, er2\n\t" \
42 "jsr @_resume\n\t" \
43 "mov.l er2,%0\n\t" \
44 : "=r" (_last) \
45 : "r" (&(prev->thread)), \
46 "r" (&(next->thread)), \
47 "g" (prev) \
48 : "cc", "er0", "er1", "er2", "er3"); \
49 (last) = _last; \
50 } while (0)
51
52 #endif /* _H8300_SWITCH_TO_H */