Subversion Repositories openrisc_2011-10-31

/* crt0.S -- startup file for hppa.
 *
 * Copyright (c) 1995 Cygnus Support
 *
 * 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.
 */
        .VERSION "1.0"
        .COPYRIGHT "crt0.o for the PA"

        .DATA

/* 
 * Set up the standard spaces (sections) These definitions come
 * from /lib/pcc_prefix.s.
 */
        .TEXT
        
/*
 * stuff we need that's defined elsewhere.
 */
        .IMPORT main, CODE
        .IMPORT exit, CODE
        .IMPORT _bss_start, DATA
        .IMPORT _end, DATA
        .IMPORT environ, DATA

/*
 * start -- set things up so the application will run.
 *
 */
        .PROC
        .CALLINFO SAVE_SP, FRAME=48
        .EXPORT $START$,ENTRY
$START$

        /* FIXME: this writes to page zero */
        ;; setup the %30 (stack pointer) with some memory
        ldil    L%_stack,%r30
        ldo     R%_stack(%r30),%r30

        ;; we need to set %r27 (global data pointer) here too 
        ldil    L%$global$,%r27
        ldo     R%$global$(%r27),%r27           ; same problem as above

/*
 * zerobss -- zero out the bss section
 */
        ; load the start of bss
        ldil    L%_bss_start,%r4
        ldo     R%_bss_start(%r4),%r4

        ;  load the end of bss
        ldil    L%_end,%r5
        ldo     R%_end(%r5),%r5


L$bssloop
        addi    -1,%r5,%r5                      ; decrement _bss_end
        stb     %r0,0(0,%r5)                    ; we do this by bytes for now even
                                                ; though it's slower, it's safer
        combf,= %r4,%r5, L$bssloop      
        nop
        
        ldi     1,%ret0

/*
 * Call the main routine from the application to get it going.
 * main (argc, argv, environ)
 * We pass argv as a pointer to NULL.
 */

        ldil    L%main,%r22
        ble     R%main(%sr4,%r22)
        copy    %r31,%r2
/*
 * Call exit() from the C library with the return value from main()
 */
        copy    %r28,%r26
        ldil    L%exit,%r22
        ble     R%exit(%sr4,%r22)
        copy    %r31,%r2

        .PROCEND
/*
 * _exit -- Exit from the application. Normally we cause a user trap
 *          to return to the ROM monitor for another run.
 */
        .EXPORT _exit, ENTRY
_exit
        .PROC
        .CALLINFO
        .ENTRY
        
        ;; This just causes a breakpoint exception
        break   0x0,0x0
        bv,n    (%rp)
        nop
        .EXIT
        .PROCEND

/*
 * _sr4export -- support for called functions. (mostly for GDB)
 */
        .EXPORT _sr4export, ENTRY
_sr4export:
        .PROC
        .CALLINFO
        .ENTRY

        ble     0(%sr4,%r22)
        copy    %r31,%rp
        ldw     -24(%sr0,%sp),%rp
        ldsid   (%sr0,%rp),%r1
        mtsp    %r1,%sr0
        be,n    0(%sr0,%rp)
        nop
        .EXIT
        .PROCEND