96 lines
3 KiB
ArmAsm
96 lines
3 KiB
ArmAsm
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/*
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* Context switch support for Hexagon
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*
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* Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
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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 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*/
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#include <asm/asm-offsets.h>
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.text
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/*
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* The register used as a fast-path thread information pointer
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* is determined as a kernel configuration option. If it happens
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* to be a callee-save register, we're going to be saving and
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* restoring it twice here.
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*
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* This code anticipates a revised ABI where R20-23 are added
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* to the set of callee-save registers, but this should be
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* backward compatible to legacy tools.
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*/
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/*
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* void switch_to(struct task_struct *prev,
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* struct task_struct *next, struct task_struct *last);
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*/
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.p2align 2
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.globl __switch_to
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.type __switch_to, @function
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/*
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* When we exit the wormhole, we need to store the previous task
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* in the new R0's pointer. Technically it should be R2, but they should
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* be the same; seems like a legacy thing. In short, don't butcher
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* R0, let it go back out unmolested.
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*/
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__switch_to:
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/*
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* Push callee-saves onto "prev" stack.
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* Here, we're sneaky because the LR and FP
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* storage of the thread_stack structure
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* is automagically allocated by allocframe,
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* so we pass struct size less 8.
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*/
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allocframe(#(_SWITCH_STACK_SIZE - 8));
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memd(R29+#(_SWITCH_R2726))=R27:26;
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memd(R29+#(_SWITCH_R2524))=R25:24;
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memd(R29+#(_SWITCH_R2322))=R23:22;
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memd(R29+#(_SWITCH_R2120))=R21:20;
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memd(R29+#(_SWITCH_R1918))=R19:18;
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memd(R29+#(_SWITCH_R1716))=R17:16;
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/* Stash thread_info pointer in task_struct */
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memw(R0+#_TASK_THREAD_INFO) = THREADINFO_REG;
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memw(R0 +#(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP)) = R29;
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/* Switch to "next" stack and restore callee saves from there */
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R29 = memw(R1 + #(_TASK_STRUCT_THREAD + _THREAD_STRUCT_SWITCH_SP));
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{
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R27:26 = memd(R29+#(_SWITCH_R2726));
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R25:24 = memd(R29+#(_SWITCH_R2524));
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}
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{
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R23:22 = memd(R29+#(_SWITCH_R2322));
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R21:20 = memd(R29+#(_SWITCH_R2120));
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}
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{
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R19:18 = memd(R29+#(_SWITCH_R1918));
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R17:16 = memd(R29+#(_SWITCH_R1716));
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}
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{
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/* THREADINFO_REG is currently one of the callee-saved regs
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* above, and so be sure to re-load it last.
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*/
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THREADINFO_REG = memw(R1 + #_TASK_THREAD_INFO);
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R31:30 = memd(R29+#_SWITCH_FP);
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}
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{
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R29 = add(R29,#_SWITCH_STACK_SIZE);
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jumpr R31;
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}
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.size __switch_to, .-__switch_to
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