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git.proxmox.com Git - mirror_ubuntu-artful-kernel.git/blob - arch/arc/kernel/ctx_sw.c
2 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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.
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
17 #include <asm/asm-offsets.h>
18 #include <linux/sched.h>
20 #define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4)
22 struct task_struct
*__sched
23 __switch_to(struct task_struct
*prev_task
, struct task_struct
*next_task
)
26 unsigned int prev
= (unsigned int)prev_task
;
27 unsigned int next
= (unsigned int)next_task
;
30 /* FP/BLINK save generated by gcc (standard function prologue */
31 "st.a r13, [sp, -4] \n\t"
32 "st.a r14, [sp, -4] \n\t"
33 "st.a r15, [sp, -4] \n\t"
34 "st.a r16, [sp, -4] \n\t"
35 "st.a r17, [sp, -4] \n\t"
36 "st.a r18, [sp, -4] \n\t"
37 "st.a r19, [sp, -4] \n\t"
38 "st.a r20, [sp, -4] \n\t"
39 "st.a r21, [sp, -4] \n\t"
40 "st.a r22, [sp, -4] \n\t"
41 "st.a r23, [sp, -4] \n\t"
42 "st.a r24, [sp, -4] \n\t"
43 #ifndef CONFIG_ARC_CURR_IN_REG
44 "st.a r25, [sp, -4] \n\t"
46 "sub sp, sp, 4 \n\t" /* usual r25 placeholder */
49 /* set ksp of outgoing task in tsk->thread.ksp */
50 #if KSP_WORD_OFF <= 255
51 "st.as sp, [%3, %1] \n\t"
54 * Workaround for NR_CPUS=4k
55 * %1 is bigger than 255 (S9 offset for st.as)
57 "add2 r24, %3, %1 \n\t"
64 * setup _current_task with incoming tsk.
65 * optionally, set r25 to that as well
66 * For SMP extra work to get to &_current_task[cpu]
67 * (open coded SET_CURR_TASK_ON_CPU)
70 "st %2, [@_current_task] \n\t"
72 "lr r24, [identity] \n\t"
73 "lsr r24, r24, 8 \n\t"
74 "bmsk r24, r24, 7 \n\t"
75 "add2 r24, @_current_task, r24 \n\t"
78 #ifdef CONFIG_ARC_CURR_IN_REG
82 /* get ksp of incoming task from tsk->thread.ksp */
83 "ld.as sp, [%2, %1] \n\t"
85 /* start loading it's CALLEE reg file */
87 #ifndef CONFIG_ARC_CURR_IN_REG
88 "ld.ab r25, [sp, 4] \n\t"
92 "ld.ab r24, [sp, 4] \n\t"
93 "ld.ab r23, [sp, 4] \n\t"
94 "ld.ab r22, [sp, 4] \n\t"
95 "ld.ab r21, [sp, 4] \n\t"
96 "ld.ab r20, [sp, 4] \n\t"
97 "ld.ab r19, [sp, 4] \n\t"
98 "ld.ab r18, [sp, 4] \n\t"
99 "ld.ab r17, [sp, 4] \n\t"
100 "ld.ab r16, [sp, 4] \n\t"
101 "ld.ab r15, [sp, 4] \n\t"
102 "ld.ab r14, [sp, 4] \n\t"
103 "ld.ab r13, [sp, 4] \n\t"
105 /* last (ret value) = prev : although for ARC it mov r0, r0 */
108 /* FP/BLINK restore generated by gcc (standard func epilogue */
111 : "n"(KSP_WORD_OFF
), "r"(next
), "r"(prev
)
115 return (struct task_struct
*)tmp
;