diff options
Diffstat (limited to 'arch/h8300/include/asm/switch_to.h')
| -rw-r--r-- | arch/h8300/include/asm/switch_to.h | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/arch/h8300/include/asm/switch_to.h b/arch/h8300/include/asm/switch_to.h new file mode 100644 index 00000000000..cdd8731ce48 --- /dev/null +++ b/arch/h8300/include/asm/switch_to.h @@ -0,0 +1,50 @@ +#ifndef _H8300_SWITCH_TO_H +#define _H8300_SWITCH_TO_H + +/* + * switch_to(n) should switch tasks to task ptr, first checking that + * ptr isn't the current task, in which case it does nothing. This + * also clears the TS-flag if the task we switched to has used the + * math co-processor latest. + */ +/* + * switch_to() saves the extra registers, that are not saved + * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and + * a0-a1. Some of these are used by schedule() and its predecessors + * and so we might get see unexpected behaviors when a task returns + * with unexpected register values. + * + * syscall stores these registers itself and none of them are used + * by syscall after the function in the syscall has been called. + * + * Beware that resume now expects *next to be in d1 and the offset of + * tss to be in a1. This saves a few instructions as we no longer have + * to push them onto the stack and read them back right after. + * + * 02/17/96 - Jes Sorensen (jds@kom.auc.dk) + * + * Changed 96/09/19 by Andreas Schwab + * pass prev in a0, next in a1, offset of tss in d1, and whether + * the mm structures are shared in d2 (to avoid atc flushing). + * + * H8/300 Porting 2002/09/04 Yoshinori Sato + */ + +asmlinkage void resume(void); +#define switch_to(prev,next,last) { \ + void *_last; \ + __asm__ __volatile__( \ + "mov.l %1, er0\n\t" \ + "mov.l %2, er1\n\t" \ + "mov.l %3, er2\n\t" \ + "jsr @_resume\n\t" \ + "mov.l er2,%0\n\t" \ + : "=r" (_last) \ + : "r" (&(prev->thread)), \ + "r" (&(next->thread)), \ + "g" (prev) \ + : "cc", "er0", "er1", "er2", "er3"); \ + (last) = _last; \ +} + +#endif /* _H8300_SWITCH_TO_H */ |