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57e26e5745
ST.as only takes S9 (255) for offset. This was going out of range when accessing a task_struct field with 4k NR_CPUS (due to 128b of coumaks itself in there). Workaround by using an intermediate register to do the address scaling. There is some duplication of fix for ctx_sw.c and ctx_sw_asm.S however given that C version will go away soon I'm not bothering to factor out the common code. Reported-by: Noam Camus <noamc@ezchip.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
117 lines
3.3 KiB
C
117 lines
3.3 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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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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#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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"sync \n\t"
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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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