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42 lines
1.5 KiB
42 lines
1.5 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _M68K_SWITCH_TO_H |
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#define _M68K_SWITCH_TO_H |
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/* |
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* switch_to(n) should switch tasks to task ptr, first checking that |
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* ptr isn't the current task, in which case it does nothing. This |
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* also clears the TS-flag if the task we switched to has used the |
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* math co-processor latest. |
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*/ |
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/* |
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* switch_to() saves the extra registers, that are not saved |
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* automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and |
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* a0-a1. Some of these are used by schedule() and its predecessors |
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* and so we might get see unexpected behaviors when a task returns |
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* with unexpected register values. |
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* |
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* syscall stores these registers itself and none of them are used |
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* by syscall after the function in the syscall has been called. |
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* |
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* Beware that resume now expects *next to be in d1 and the offset of |
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* tss to be in a1. This saves a few instructions as we no longer have |
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* to push them onto the stack and read them back right after. |
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* |
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* 02/17/96 - Jes Sorensen ([email protected]) |
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* |
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* Changed 96/09/19 by Andreas Schwab |
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* pass prev in a0, next in a1 |
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*/ |
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asmlinkage void resume(void); |
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#define switch_to(prev,next,last) do { \ |
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register void *_prev __asm__ ("a0") = (prev); \ |
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register void *_next __asm__ ("a1") = (next); \ |
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register void *_last __asm__ ("d1"); \ |
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__asm__ __volatile__("jbsr resume" \ |
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: "=a" (_prev), "=a" (_next), "=d" (_last) \ |
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: "0" (_prev), "1" (_next) \ |
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: "d0", "d2", "d3", "d4", "d5"); \ |
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(last) = _last; \ |
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} while (0) |
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#endif /* _M68K_SWITCH_TO_H */
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