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