1d215b1285
instead of a PCPU field for curthread. This averts a race on SMP systems with a high interrupt rate where the thread looking up the value of curthread could be preempted and migrated between obtaining the PCPU pointer and reading the value of pc_curthread, resulting in curthread being observed to be the current thread on the thread's original CPU. This played merry havoc with the system, in particular with mutexes. Many thanks to jhb for helping me work this one out. Note that Book-E is in principle susceptible to the same problem, but has not been modified yet due to lack of Book-E hardware. MFC after: 2 weeks
157 lines
3.7 KiB
ArmAsm
157 lines
3.7 KiB
ArmAsm
/*-
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* Copyright (C) 2009-2011 Nathan Whitehorn
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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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* 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 TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/syscall.h>
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#include <machine/trap.h>
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#include <machine/param.h>
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#include <machine/spr.h>
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#include <machine/asm.h>
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#define OFWSTKSZ 4096 /* 4K Open Firmware stack */
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/*
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* Globals
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*/
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.data
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GLOBAL(ofmsr)
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.long 0, 0, 0, 0, 0 /* msr/sprg0-3 used in Open Firmware */
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GLOBAL(rtasmsr)
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.long 0
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GLOBAL(openfirmware_entry)
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.long 0 /* Open Firmware entry point */
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GLOBAL(rtas_entry)
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.long 0 /* RTAS entry point */
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.align 4
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ofwstk:
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.space OFWSTKSZ
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rtas_regsave:
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.space 4
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/*
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* Open Firmware Entry Point. May need to enter real mode.
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*
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* C prototype: int ofwcall(void *callbuffer);
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*/
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ASENTRY(ofwcall)
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mflr %r0
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stw %r0,4(%r1)
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/* Record the old MSR */
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mfmsr %r6
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/* read client interface handler */
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lis %r4,openfirmware_entry@ha
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lwz %r4,openfirmware_entry@l(%r4)
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/*
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* Set the MSR to the OF value. This has the side effect of disabling
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* exceptions, which prevents preemption later.
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*/
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lis %r5,ofmsr@ha
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lwz %r5,ofmsr@l(%r5)
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mtmsr %r5
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isync
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/*
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* Set up OF stack. This needs to be potentially accessible in real mode
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* The pointer to the current kernel stack is placed at the very
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* top of the stack along with the old MSR so we can get them back
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* later.
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*/
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mr %r5,%r1
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lis %r1,(ofwstk+OFWSTKSZ-32)@ha
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addi %r1,%r1,(ofwstk+OFWSTKSZ-32)@l
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stw %r5,20(%r1) /* Save real stack pointer */
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stw %r2,24(%r1) /* Save curthread */
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stw %r6,28(%r1) /* Save old MSR */
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li %r5,0
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stw %r5,4(%r1)
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stw %r5,0(%r1)
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/* Finally, branch to OF */
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mtctr %r4
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bctrl
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/* Reload stack pointer and MSR from the OFW stack */
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lwz %r6,28(%r1)
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lwz %r2,24(%r1)
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lwz %r1,20(%r1)
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/* Now set the real MSR */
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mtmsr %r6
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isync
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/* Return */
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lwz %r0,4(%r1)
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mtlr %r0
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blr
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/*
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* RTAS Entry Point. Similar to the OF one, but simpler (no separate stack)
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*
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* C prototype: int rtascall(void *callbuffer, void *rtas_privdat);
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*/
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ASENTRY(rtascall)
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mflr %r0
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stw %r0,4(%r1)
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/* Record the old MSR to real-mode-accessible area */
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mfmsr %r0
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lis %r5,rtas_regsave@ha
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stw %r0,rtas_regsave@l(%r5)
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/* read client interface handler */
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lis %r5,rtas_entry@ha
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lwz %r5,rtas_entry@l(%r5)
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/* Set the MSR to the RTAS value */
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lis %r6,rtasmsr@ha
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lwz %r6,rtasmsr@l(%r6)
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mtmsr %r6
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isync
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/* Branch to RTAS */
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mtctr %r5
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bctrl
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/* Now set the MSR back */
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lis %r6,rtas_regsave@ha
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lwz %r6,rtas_regsave@l(%r6)
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mtmsr %r6
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isync
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/* And return */
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lwz %r0,4(%r1)
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mtlr %r0
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blr
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