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112 lines
3.1 KiB
112 lines
3.1 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com) |
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* |
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* Vineetg: Aug 2009 |
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* -"C" version of lowest level context switch asm macro called by schedular |
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* gcc doesn't generate the dward CFI info for hand written asm, hence can't |
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* backtrace out of it (e.g. tasks sleeping in kernel). |
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* So we cheat a bit by writing almost similar code in inline-asm. |
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* -This is a hacky way of doing things, but there is no other simple way. |
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* I don't want/intend to extend unwinding code to understand raw asm |
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*/ |
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#include <asm/asm-offsets.h> |
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#include <linux/sched.h> |
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#include <linux/sched/debug.h> |
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#define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4) |
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struct task_struct *__sched |
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__switch_to(struct task_struct *prev_task, struct task_struct *next_task) |
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{ |
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unsigned int tmp; |
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unsigned int prev = (unsigned int)prev_task; |
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unsigned int next = (unsigned int)next_task; |
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__asm__ __volatile__( |
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/* FP/BLINK save generated by gcc (standard function prologue */ |
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"st.a r13, [sp, -4] \n\t" |
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"st.a r14, [sp, -4] \n\t" |
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"st.a r15, [sp, -4] \n\t" |
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"st.a r16, [sp, -4] \n\t" |
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"st.a r17, [sp, -4] \n\t" |
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"st.a r18, [sp, -4] \n\t" |
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"st.a r19, [sp, -4] \n\t" |
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"st.a r20, [sp, -4] \n\t" |
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"st.a r21, [sp, -4] \n\t" |
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"st.a r22, [sp, -4] \n\t" |
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"st.a r23, [sp, -4] \n\t" |
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"st.a r24, [sp, -4] \n\t" |
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#ifndef CONFIG_ARC_CURR_IN_REG |
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"st.a r25, [sp, -4] \n\t" |
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#else |
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"sub sp, sp, 4 \n\t" /* usual r25 placeholder */ |
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#endif |
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/* set ksp of outgoing task in tsk->thread.ksp */ |
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#if KSP_WORD_OFF <= 255 |
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"st.as sp, [%3, %1] \n\t" |
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#else |
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/* |
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* Workaround for NR_CPUS=4k |
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* %1 is bigger than 255 (S9 offset for st.as) |
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*/ |
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"add2 r24, %3, %1 \n\t" |
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"st sp, [r24] \n\t" |
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#endif |
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/* |
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* setup _current_task with incoming tsk. |
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* optionally, set r25 to that as well |
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* For SMP extra work to get to &_current_task[cpu] |
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* (open coded SET_CURR_TASK_ON_CPU) |
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*/ |
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#ifndef CONFIG_SMP |
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"st %2, [@_current_task] \n\t" |
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#else |
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"lr r24, [identity] \n\t" |
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"lsr r24, r24, 8 \n\t" |
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"bmsk r24, r24, 7 \n\t" |
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"add2 r24, @_current_task, r24 \n\t" |
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"st %2, [r24] \n\t" |
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#endif |
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#ifdef CONFIG_ARC_CURR_IN_REG |
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"mov r25, %2 \n\t" |
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#endif |
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/* get ksp of incoming task from tsk->thread.ksp */ |
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"ld.as sp, [%2, %1] \n\t" |
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/* start loading it's CALLEE reg file */ |
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#ifndef CONFIG_ARC_CURR_IN_REG |
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"ld.ab r25, [sp, 4] \n\t" |
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#else |
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"add sp, sp, 4 \n\t" |
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#endif |
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"ld.ab r24, [sp, 4] \n\t" |
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"ld.ab r23, [sp, 4] \n\t" |
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"ld.ab r22, [sp, 4] \n\t" |
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"ld.ab r21, [sp, 4] \n\t" |
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"ld.ab r20, [sp, 4] \n\t" |
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"ld.ab r19, [sp, 4] \n\t" |
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"ld.ab r18, [sp, 4] \n\t" |
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"ld.ab r17, [sp, 4] \n\t" |
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"ld.ab r16, [sp, 4] \n\t" |
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"ld.ab r15, [sp, 4] \n\t" |
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"ld.ab r14, [sp, 4] \n\t" |
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"ld.ab r13, [sp, 4] \n\t" |
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/* last (ret value) = prev : although for ARC it mov r0, r0 */ |
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"mov %0, %3 \n\t" |
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/* FP/BLINK restore generated by gcc (standard func epilogue */ |
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: "=r"(tmp) |
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: "n"(KSP_WORD_OFF), "r"(next), "r"(prev) |
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: "blink" |
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); |
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return (struct task_struct *)tmp; |
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}
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