8955f59879
that we can flush the register stack prior to entering the kernel. This avoids having dirty registers and saves us from having to manually write them to the backing store from within the kernel. In that respect, flushing the RSE is both functionally required as well as performance optimal. On average we had 18 dirty registers when getcontext(2) was called from libthr. Since libthr does not switch back to a context created by getcontext(2), not having dealt with the dirty registers was harmless.
40 lines
1.5 KiB
ArmAsm
40 lines
1.5 KiB
ArmAsm
/*
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* Copyright (c) 2003 Marcel Moolenaar
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <machine/asm.h>
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__FBSDID("$FreeBSD$");
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#include "SYS.h"
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ENTRY(__sys_getcontext,2)
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WEAK_ALIAS(getcontext, __sys_getcontext)
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WEAK_ALIAS(_getcontext, __sys_getcontext)
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flushrs
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;;
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CALLSYS_ERROR(getcontext)
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br.ret.sptk.few rp
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END(__sys_getcontext)
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