98 lines
3.6 KiB
ArmAsm
98 lines
3.6 KiB
ArmAsm
/*
|
|
* 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.
|
|
*/
|
|
|
|
/*
|
|
* crt0.o for MIPS r2000/r3000.
|
|
*
|
|
* crt stands for "C runtime".
|
|
*
|
|
* Basically, this is the startup code that gets invoked before main(),
|
|
* and regains control when main returns.
|
|
*
|
|
* All we really do is save copies of argv and environ for use by libc
|
|
* funcions (e.g. err* and warn*), and call exit when main returns.
|
|
*/
|
|
|
|
#include <kern/mips/regdefs.h>
|
|
#include <kern/syscall.h>
|
|
|
|
.set noreorder /* so we can use delay slots explicitly */
|
|
|
|
.text
|
|
.globl __start
|
|
.type __start,@function
|
|
.ent __start
|
|
__start:
|
|
/* Load the "global pointer" register */
|
|
la gp, _gp
|
|
|
|
/*
|
|
* We expect that the kernel passes argc in a0, argv in a1,
|
|
* and environ in a2. We do not expect the kernel to set up a
|
|
* complete stack frame, however.
|
|
*
|
|
* The MIPS ABI decrees that every caller will leave 16 bytes of
|
|
* space in the bottom of its stack frame for writing back the
|
|
* values of a0-a3, even when calling functions that take fewer
|
|
* than four arguments. It also requires the stack to be aligned
|
|
* to an 8-byte boundary. (This is because of 64-bit MIPS, which
|
|
* we're not dealing with... but we'll conform to the standard.)
|
|
*/
|
|
li t0, 0xfffffff8 /* mask for stack alignment */
|
|
and sp, sp, t0 /* align the stack */
|
|
addiu sp, sp, -16 /* create our frame */
|
|
|
|
sw a1, __argv /* save second arg (argv) in __argv for use later */
|
|
sw a2, __environ /* save third arg (environ) for use later */
|
|
|
|
jal main /* call main */
|
|
nop /* delay slot */
|
|
|
|
/*
|
|
* Now, we have the return value of main in v0.
|
|
*
|
|
* Move it to s0 (which is callee-save) so we still have
|
|
* it in case exit() returns.
|
|
*
|
|
* Also move it to a0 so it's the argument to exit.
|
|
*/
|
|
move s0, v0 /* save return value */
|
|
1:
|
|
jal exit /* call exit() */
|
|
move a0, s0 /* Set argument (in delay slot) */
|
|
|
|
/*
|
|
* exit() does not return. (Even if _exit() is not implemented
|
|
* so *it* returns, exit() is supposed to take care of that.)
|
|
* But just in case, loop and try again.
|
|
*/
|
|
b 1b /* loop back */
|
|
nop /* delay slot */
|
|
.end __start
|