1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
|
#ifndef _M68K_SWITCH_TO_H
#define _M68K_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
*/
asmlinkage void resume(void);
#define switch_to(prev,next,last) do { \
register void *_prev __asm__ ("a0") = (prev); \
register void *_next __asm__ ("a1") = (next); \
register void *_last __asm__ ("d1"); \
__asm__ __volatile__("jbsr resume" \
: "=a" (_prev), "=a" (_next), "=d" (_last) \
: "0" (_prev), "1" (_next) \
: "d0", "d2", "d3", "d4", "d5"); \
(last) = _last; \
} while (0)
#endif /* _M68K_SWITCH_TO_H */
|
