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/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Vineetg: Aug 2009
* -"C" version of lowest level context switch asm macro called by schedular
* gcc doesn't generate the dward CFI info for hand written asm, hence can't
* backtrace out of it (e.g. tasks sleeping in kernel).
* So we cheat a bit by writing almost similar code in inline-asm.
* -This is a hacky way of doing things, but there is no other simple way.
* I don't want/intend to extend unwinding code to understand raw asm
*/
#include <asm/asm-offsets.h>
#include <linux/sched.h>
#define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4)
struct task_struct *__sched
__switch_to(struct task_struct *prev_task, struct task_struct *next_task)
{
unsigned int tmp;
unsigned int prev = (unsigned int)prev_task;
unsigned int next = (unsigned int)next_task;
__asm__ __volatile__(
/* FP/BLINK save generated by gcc (standard function prologue */
"st.a r13, [sp, -4] \n\t"
"st.a r14, [sp, -4] \n\t"
"st.a r15, [sp, -4] \n\t"
"st.a r16, [sp, -4] \n\t"
"st.a r17, [sp, -4] \n\t"
"st.a r18, [sp, -4] \n\t"
"st.a r19, [sp, -4] \n\t"
"st.a r20, [sp, -4] \n\t"
"st.a r21, [sp, -4] \n\t"
"st.a r22, [sp, -4] \n\t"
"st.a r23, [sp, -4] \n\t"
"st.a r24, [sp, -4] \n\t"
#ifndef CONFIG_ARC_CURR_IN_REG
"st.a r25, [sp, -4] \n\t"
#else
"sub sp, sp, 4 \n\t" /* usual r25 placeholder */
#endif
/* set ksp of outgoing task in tsk->thread.ksp */
#if KSP_WORD_OFF <= 255
"st.as sp, [%3, %1] \n\t"
#else
/*
* Workaround for NR_CPUS=4k
* %1 is bigger than 255 (S9 offset for st.as)
*/
"add2 r24, %3, %1 \n\t"
"st sp, [r24] \n\t"
#endif
/*
* setup _current_task with incoming tsk.
* optionally, set r25 to that as well
* For SMP extra work to get to &_current_task[cpu]
* (open coded SET_CURR_TASK_ON_CPU)
*/
#ifndef CONFIG_SMP
"st %2, [@_current_task] \n\t"
#else
"lr r24, [identity] \n\t"
"lsr r24, r24, 8 \n\t"
"bmsk r24, r24, 7 \n\t"
"add2 r24, @_current_task, r24 \n\t"
"st %2, [r24] \n\t"
#endif
#ifdef CONFIG_ARC_CURR_IN_REG
"mov r25, %2 \n\t"
#endif
/* get ksp of incoming task from tsk->thread.ksp */
"ld.as sp, [%2, %1] \n\t"
/* start loading it's CALLEE reg file */
#ifndef CONFIG_ARC_CURR_IN_REG
"ld.ab r25, [sp, 4] \n\t"
#else
"add sp, sp, 4 \n\t"
#endif
"ld.ab r24, [sp, 4] \n\t"
"ld.ab r23, [sp, 4] \n\t"
"ld.ab r22, [sp, 4] \n\t"
"ld.ab r21, [sp, 4] \n\t"
"ld.ab r20, [sp, 4] \n\t"
"ld.ab r19, [sp, 4] \n\t"
"ld.ab r18, [sp, 4] \n\t"
"ld.ab r17, [sp, 4] \n\t"
"ld.ab r16, [sp, 4] \n\t"
"ld.ab r15, [sp, 4] \n\t"
"ld.ab r14, [sp, 4] \n\t"
"ld.ab r13, [sp, 4] \n\t"
/* last (ret value) = prev : although for ARC it mov r0, r0 */
"mov %0, %3 \n\t"
/* FP/BLINK restore generated by gcc (standard func epilogue */
: "=r"(tmp)
: "n"(KSP_WORD_OFF), "r"(next), "r"(prev)
: "blink"
);
return (struct task_struct *)tmp;
}
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