/* [<][>][^][v][top][bottom][index][help] */
DEFINITIONS
This source file includes following definitions.
- switchframe_init
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <types.h>
31 #include <lib.h>
32 #include <thread.h>
33 #include <threadprivate.h>
34
35 #include "switchframe.h"
36
37 /* in threadstart.S */
38 extern void mips_threadstart(/* arguments are in unusual registers */);
39
40
41 /*
42 * Function to initialize the switchframe of a new thread, which is
43 * *not* the one that is currently running.
44 *
45 * The new thread should, when it is run the first time, end up calling
46 * thread_startup(entrypoint, data1, data2).
47 *
48 * We arrange for this by creating a phony switchframe for
49 * switchframe_switch() to switch to. The only trouble is that the
50 * switchframe doesn't include the argument registers a0-a3. So we
51 * store the arguments in the s* registers, and use a bit of asm
52 * (mips_threadstart) to move them and then jump to thread_startup.
53 */
54 void
55 switchframe_init(struct thread *thread,
56 void (*entrypoint)(void *data1, unsigned long data2),
57 void *data1, unsigned long data2)
58 {
59 vaddr_t stacktop;
60 struct switchframe *sf;
61
62 /*
63 * MIPS stacks grow down. t_stack is just a hunk of memory, so
64 * get the other end of it. Then set up a switchframe on the
65 * top of the stack.
66 */
67 stacktop = ((vaddr_t)thread->t_stack) + STACK_SIZE;
68 sf = ((struct switchframe *) stacktop) - 1;
69
70 /* Zero out the switchframe. */
71 bzero(sf, sizeof(*sf));
72
73 /*
74 * Now set the important parts: pass through the three arguments,
75 * and set the return address register to the place we want
76 * execution to begin.
77 *
78 * Thus, when switchframe_switch does its "j ra", it will
79 * actually jump to mips_threadstart, which will move the
80 * arguments into the right register and jump to
81 * thread_startup().
82 *
83 * Note that this means that when we call switchframe_switch()
84 * in thread_switch(), we may not come back out the same way
85 * in the next thread. (Though we will come back out the same
86 * way when we later come back to the same thread again.)
87 *
88 * This has implications for code at the bottom of
89 * thread_switch, described in thread.c.
90 */
91 sf->sf_s0 = (uint32_t)entrypoint;
92 sf->sf_s1 = (uint32_t)data1;
93 sf->sf_s2 = (uint32_t)data2;
94 sf->sf_ra = (uint32_t)mips_threadstart;
95
96 /* Set ->t_context, and we're done. */
97 thread->t_context = sf;
98 }