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