switch_to.h
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#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) \
do { \
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; \
} while (0)
#endif /* _H8300_SWITCH_TO_H */