99 lines
3.9 KiB
C
99 lines
3.9 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
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* The President and Fellows of Harvard College.
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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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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <types.h>
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#include <lib.h>
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#include <thread.h>
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#include <threadprivate.h>
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#include "switchframe.h"
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/* in threadstart.S */
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extern void mips_threadstart(/* arguments are in unusual registers */);
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/*
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* Function to initialize the switchframe of a new thread, which is
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* *not* the one that is currently running.
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*
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* The new thread should, when it is run the first time, end up calling
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* thread_startup(entrypoint, data1, data2).
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*
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* We arrange for this by creating a phony switchframe for
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* switchframe_switch() to switch to. The only trouble is that the
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* switchframe doesn't include the argument registers a0-a3. So we
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* store the arguments in the s* registers, and use a bit of asm
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* (mips_threadstart) to move them and then jump to thread_startup.
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*/
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void
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switchframe_init(struct thread *thread,
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void (*entrypoint)(void *data1, unsigned long data2),
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void *data1, unsigned long data2)
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{
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vaddr_t stacktop;
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struct switchframe *sf;
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/*
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* MIPS stacks grow down. t_stack is just a hunk of memory, so
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* get the other end of it. Then set up a switchframe on the
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* top of the stack.
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*/
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stacktop = ((vaddr_t)thread->t_stack) + STACK_SIZE;
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sf = ((struct switchframe *) stacktop) - 1;
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/* Zero out the switchframe. */
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bzero(sf, sizeof(*sf));
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/*
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* Now set the important parts: pass through the three arguments,
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* and set the return address register to the place we want
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* execution to begin.
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*
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* Thus, when switchframe_switch does its "j ra", it will
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* actually jump to mips_threadstart, which will move the
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* arguments into the right register and jump to
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* thread_startup().
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*
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* Note that this means that when we call switchframe_switch()
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* in thread_switch(), we may not come back out the same way
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* in the next thread. (Though we will come back out the same
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* way when we later come back to the same thread again.)
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*
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* This has implications for code at the bottom of
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* thread_switch, described in thread.c.
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*/
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sf->sf_s0 = (uint32_t)entrypoint;
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sf->sf_s1 = (uint32_t)data1;
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sf->sf_s2 = (uint32_t)data2;
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sf->sf_ra = (uint32_t)mips_threadstart;
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/* Set ->t_context, and we're done. */
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thread->t_context = sf;
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}
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