source: trunk/libs/newlib/src/libgloss/mips/crt0_cygmon.S @ 675

/*
 * crt0_cygmon.S -- Minimal startup file for MIPS targets running Cygmon.
 *
 * Copyright (c) 1995, 1996, 1997, 2000 Red Hat, Inc.
 *
 * The authors hereby grant permission to use, copy, modify, distribute,
 * and license this software and its documentation for any purpose, provided
 * that existing copyright notices are retained in all copies and that this
 * notice is included verbatim in any distributions. No written agreement,
 * license, or royalty fee is required for any of the authorized uses.
 * Modifications to this software may be copyrighted by their authors
 * and need not follow the licensing terms described here, provided that
 * the new terms are clearly indicated on the first page of each file where
 * they apply.
 */

/*
 * This file contains the minimal startup code necessary.
 * This will not do any hardware initialization.  It is assumed that we are talking to Cygmon
 * and therefore the hardware will be initialized properly.
 */

#ifdef __mips16
/* This file contains 32 bit assembly code.  */
        .set nomips16
#endif

#include "regs.S"

/*
 * Set up some room for a stack. We just grab a chunk of memory.
 */
#define STACK_SIZE  0x4000
#define GLOBAL_SIZE 0x2000

#define STARTUP_STACK_SIZE      0x0100

        .comm   __memsize, 12
        .comm   __lstack, STARTUP_STACK_SIZE
        .comm   __stackbase,4

        .text
        .align  4
    /*
     * Without the following nop, GDB thinks _start is a data variable.
     * This is probably a bug in GDB in handling a symbol that is at the
     * start of the .text section.
     */
        nop

        .globl  _start
        .ent    _start
_start:
        .set    noreorder
        la              gp, _gp                                 # set the global data pointer, defined in the linker script
        .end    _start

    /*
     * zero out the bss section.
     */
        .globl  __memsize
        .globl  get_mem_info .text
        .globl  zerobss
        .ent    zerobss
zerobss:
        la              v0, _fbss                               # These variables are defined in the linker script
        la              v1, _end

3:
        sw              zero, 0(v0)
        bltu    v0, v1, 3b
        addiu   v0, v0, 4                               # executed in delay slot

    /*
     * Setup a small stack so we can run some C code,
     * and get the usable memory size.
     */
        la              t0, __lstack
        addiu   sp, t0, STARTUP_STACK_SIZE
        la              a0, __memsize
        jal             get_mem_info
        nop

        /*
     * Setup the stack pointer -- 
     *    get_mem_info returns the top of memory, so just use that In
     *    addition, we must subtract 24 bytes for the 3 8 byte
     *    arguments to main, in case main wants to write them back to
     *    the stack.  The caller is supposed to allocate stack space
     *    for parameters in registers in the old MIPS ABIs.  We must
     *    do this even though we aren't passing arguments, because
     *    main might be declared to have them.
         *    Some ports need a larger alignment for the stack, so we
         *    subtract 32, which satisifes the stack for the arguments and
         *    keeps the stack pointer better aligned.
     */
        subu    v0, v0, 32
        move    sp, v0

        sw              sp, __stackbase                 # keep this for future ref
        .end    zerobss

    /*
     * initialize target specific stuff. Only execute these
     * functions it they exist.
     */
        .globl  hardware_init_hook .text
        .globl  software_init_hook .text
        .globl  __do_global_dtors .text
        .globl  atexit .text
        .globl  exit .text
        .globl  init
        .ent    init
init:
        la              t9, hardware_init_hook  # init the hardware if needed
        beq             t9, zero, 6f
        nop
        jal             t9
        nop
6:
        la              t9, software_init_hook  # init the software if needed
        beq             t9, zero, 7f
        nop
        jal             t9
        nop
7:
        la              a0, __do_global_dtors
        jal             atexit
        nop

#ifdef GCRT0
        .globl  _ftext
        .globl  _extext
        la              a0, _ftext
        la              a1, _etext
        jal             monstartup
        nop
#endif

        move    a0,zero                                 # set argc to 0
        jal             main                                    # call the program start function
        nop

        # fall through to the "exit" routine
        jal             exit                                    # call libc exit to run the G++
                                                                        # destructors
        move    a0, v0                                  # pass through the exit code
        .end    init
        
/*
 * _exit -- Exit from the application. Normally we cause a user trap
 *          to return to the ROM monitor for another run. NOTE: This is
 *          the only other routine we provide in the crt0.o object, since
 *          it may be tied to the "_start" routine. It also allows
 *          executables that contain a complete world to be linked with
 *          just the crt0.o object.
 */
        .globl  _exit
        .ent    _exit
_exit:
7:
#ifdef GCRT0
        jal             _mcleanup
        nop
#endif
        # Cygmon expects a break 5
        break   5
        nop
        b               7b                                              # loop back just in-case
        nop
        .end    _exit

/* EOF crt0.S */