1 /*
2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * Vineetg: Aug 2009
9 * -"C" version of lowest level context switch asm macro called by schedular
10 * gcc doesn't generate the dward CFI info for hand written asm, hence can't
11 * backtrace out of it (e.g. tasks sleeping in kernel).
12 * So we cheat a bit by writing almost similar code in inline-asm.
13 * -This is a hacky way of doing things, but there is no other simple way.
14 * I don't want/intend to extend unwinding code to understand raw asm
15 */
16
17 #include <asm/asm-offsets.h>
18 #include <linux/sched.h>
19 #include <linux/sched/debug.h>
20 #ifdef CONFIG_ARC_PLAT_EZNPS
21 #include <plat/ctop.h>
22 #endif
23
24 #define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4)
25
26 struct task_struct *__sched
__switch_to(struct task_struct * prev_task,struct task_struct * next_task)27 __switch_to(struct task_struct *prev_task, struct task_struct *next_task)
28 {
29 unsigned int tmp;
30 unsigned int prev = (unsigned int)prev_task;
31 unsigned int next = (unsigned int)next_task;
32
33 __asm__ __volatile__(
34 /* FP/BLINK save generated by gcc (standard function prologue */
35 "st.a r13, [sp, -4] \n\t"
36 "st.a r14, [sp, -4] \n\t"
37 "st.a r15, [sp, -4] \n\t"
38 "st.a r16, [sp, -4] \n\t"
39 "st.a r17, [sp, -4] \n\t"
40 "st.a r18, [sp, -4] \n\t"
41 "st.a r19, [sp, -4] \n\t"
42 "st.a r20, [sp, -4] \n\t"
43 "st.a r21, [sp, -4] \n\t"
44 "st.a r22, [sp, -4] \n\t"
45 "st.a r23, [sp, -4] \n\t"
46 "st.a r24, [sp, -4] \n\t"
47 #ifndef CONFIG_ARC_CURR_IN_REG
48 "st.a r25, [sp, -4] \n\t"
49 #else
50 "sub sp, sp, 4 \n\t" /* usual r25 placeholder */
51 #endif
52
53 /* set ksp of outgoing task in tsk->thread.ksp */
54 #if KSP_WORD_OFF <= 255
55 "st.as sp, [%3, %1] \n\t"
56 #else
57 /*
58 * Workaround for NR_CPUS=4k
59 * %1 is bigger than 255 (S9 offset for st.as)
60 */
61 "add2 r24, %3, %1 \n\t"
62 "st sp, [r24] \n\t"
63 #endif
64
65 /*
66 * setup _current_task with incoming tsk.
67 * optionally, set r25 to that as well
68 * For SMP extra work to get to &_current_task[cpu]
69 * (open coded SET_CURR_TASK_ON_CPU)
70 */
71 #ifndef CONFIG_SMP
72 "st %2, [@_current_task] \n\t"
73 #else
74 #ifdef CONFIG_ARC_PLAT_EZNPS
75 "lr r24, [%4] \n\t"
76 #ifndef CONFIG_EZNPS_MTM_EXT
77 "lsr r24, r24, 4 \n\t"
78 #endif
79 #else
80 "lr r24, [identity] \n\t"
81 "lsr r24, r24, 8 \n\t"
82 "bmsk r24, r24, 7 \n\t"
83 #endif
84 "add2 r24, @_current_task, r24 \n\t"
85 "st %2, [r24] \n\t"
86 #endif
87 #ifdef CONFIG_ARC_CURR_IN_REG
88 "mov r25, %2 \n\t"
89 #endif
90
91 /* get ksp of incoming task from tsk->thread.ksp */
92 "ld.as sp, [%2, %1] \n\t"
93
94 /* start loading it's CALLEE reg file */
95
96 #ifndef CONFIG_ARC_CURR_IN_REG
97 "ld.ab r25, [sp, 4] \n\t"
98 #else
99 "add sp, sp, 4 \n\t"
100 #endif
101 "ld.ab r24, [sp, 4] \n\t"
102 "ld.ab r23, [sp, 4] \n\t"
103 "ld.ab r22, [sp, 4] \n\t"
104 "ld.ab r21, [sp, 4] \n\t"
105 "ld.ab r20, [sp, 4] \n\t"
106 "ld.ab r19, [sp, 4] \n\t"
107 "ld.ab r18, [sp, 4] \n\t"
108 "ld.ab r17, [sp, 4] \n\t"
109 "ld.ab r16, [sp, 4] \n\t"
110 "ld.ab r15, [sp, 4] \n\t"
111 "ld.ab r14, [sp, 4] \n\t"
112 "ld.ab r13, [sp, 4] \n\t"
113
114 /* last (ret value) = prev : although for ARC it mov r0, r0 */
115 "mov %0, %3 \n\t"
116
117 /* FP/BLINK restore generated by gcc (standard func epilogue */
118
119 : "=r"(tmp)
120 : "n"(KSP_WORD_OFF), "r"(next), "r"(prev)
121 #ifdef CONFIG_ARC_PLAT_EZNPS
122 , "i"(CTOP_AUX_LOGIC_GLOBAL_ID)
123 #endif
124 : "blink"
125 );
126
127 return (struct task_struct *)tmp;
128 }
129
