source: trunk/libs/newlib/src/libgloss/nds32/crt1.S @ 573

/*
Copyright (c) 2013-2014 Andes Technology Corporation.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    Redistributions of source code must retain the above copyright
    notice, this list of conditions and the following disclaimer.

    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.

    The name of the company may not be used to endorse or promote
    products derived from this software without specific prior written
    permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 RED HAT INCORPORATED 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.
*/

##==============================================================================
##
##      crt1.S
##
##      nds32 startup code
##
##==============================================================================

#include "syscall_extra.h"

##------------------------------------------------------------------------------
## Vector table setup
##------------------------------------------------------------------------------
        .section        .nds32_init, "ax"
        j       _start

##------------------------------------------------------------------------------
## Startup code implementation
##------------------------------------------------------------------------------
        .section        .text
        .weak   _SDA_BASE_
        .weak   _ITB_BASE_
        .weak   _arg_init
        .weak   __pre_c_init
        .weak   __post_c_init
        .weak   _call_exit
        .global _start
        .type   _start, @function
        .align  2
_start:
        /* The initialization sequence really does matter !!!
           The global pointer must be
           initialized precedence over all others.  */

.L_init_gp:
        /* Initialization for global pointer.  The symbol _SDA_BASE_ is
           determined by Linker.  SDA stands for Small Data Access.  */
        la      $gp, _SDA_BASE_

#if __NDS32_EXT_EX9__
.L_init_itb:
        /* Initialization for Instruction Table Base (ITB).
           The symbol _ITB_BASE_ is determined by Linker.
           Set $ITB only if MSC_CFG.EIT (cr4.b'24) is set.  */
        mfsr    $r0, $MSC_CFG
        srli    $r0, $r0, 24
        andi    $r0, $r0, 0x1
        beqz    $r0, 1f         /* Fall through ?  */
        la      $r0, _ITB_BASE_
        mtusr   $r0, $ITB
1:
#endif

.L_init_sp:
        /* Initialization for stack pointer.  The symbol _stack is defined
           in linker script.  Make sure $sp is 8-byte aligned.  */
        la      $sp, _stack
#if __NDS32_ISA_V3__
        bitci   $sp, $sp, #7
#else
        movi    $r0, #-8                /* Set $r0 as 0xFFFFFFF8.  */
        and     $sp, $sp, $r0
#endif

#if __NDS32_EXT_FPU_SP__ || __NDS32_EXT_FPU_DP__
.L_init_fpu:
        /* Initialize FPU
           Set FUCOP_CTL.CP0EN (fucpr.b'0).  */
        mfsr    $r0, $FUCOP_CTL
        ori     $r0, $r0, 0x1
        mtsr    $r0, $FUCOP_CTL
        dsb
        /* According to [bugzilla #9425], set flush-to-zero mode.
           That is, set $FPCSR.DNZ(b'12) = 1.  */
        FMFCSR  $r0
        ori     $r0, $r0, 0x1000
        FMTCSR  $r0
        dsb
#endif

.L_pre_c_init:
        ! call __pre_c_init if provided
        ! sample __pre_c_init is in BSP
        la      $r15, __pre_c_init      ! load address of __pre_c_init
        beqz    $r15, .L_zero_out_bss   ! check existence of __pre_c_init
        jral    $r15                    ! pre-c-runtime initialization

.L_zero_out_bss:
        /* Zero out the bss section.
           Equivalence C code for follow part:
           if (_end == _edata) goto .L_call_main
           unsinged int *ptr = _edata;
           while (ptr != _end)
             *ptr++ = 0
           $r0 = ptr/_edata
           $r1 = _end
           $r2 = 0
         */
        la      $r0, _edata
        la      $r1, _end
        movi    $r2, #0
        beq     $r0, $r1, .L_cpp_init   /* Branch if no bss.  */
.Lword_clear:
        swi.bi  $r2, [$r0], #4
        bne     $r0, $r1, .Lword_clear

.L_cpp_init:
        /* Call '_init' to invoke constructors.  */
        jal     _init
        /* Register '_fini' into atexit() to invoke destructors when
           exit() has been reached.  */
        la      $r0, _fini
        jal     atexit

.L_post_c_init:
        ! call __post_c_init if provided
        ! no sample __post_c_init is provided
        la      $r15, __post_c_init     ! load address of __post_c_init
        beqz    $r15, .L_arg_init       ! check existence of __post_c_init
        jral    $r15                    ! post-c-runtime initialization

.L_arg_init:
        ! argc/argv initialization if necessary
        la      $r7, _arg_init          ! get address of _arg_init
        beqz    $r7, .L_clean_reg       ! if there isn't _arg_init, go main
        addi    $sp, $sp, -512          ! allocate space for command line
                                        ! and arguments
        move    $r6, $sp                ! r6 = buffer addr of cmd line
        move    $r0, $r6                ! r0 = buffer addr of cmd line
        syscall SYS_getcmdline          ! get cmd line
        move    $r0, $r6                ! r0 = buffer addr of cmd line
        addi    $r1, $r6, 256           ! r1 = argv
        jral    $r7                     ! init argc/argv
        addi    $r1, $r6, 256           ! r1 = argv
        b       .L_call_main

.L_clean_reg:
        /* Prepare argc/argv/env for main function.
           Since there is no operating system so far,
           we set $r0, $r1, and $r2 to be zero.
           Note: $r2 already set to zero in .L_zero_out_bss: code fragment.  */
        movi    $r0, 0
        movi    $r1, 0
        movi    $r2, 0

.L_call_main:
        /* Call 'main'.  */
        bal     main

        /* Call _call_exit.  */
        ! call _call_exit if necessary; default implementation is in crtexit.c
        la      $r15, _call_exit                ! load address of _call_exit
        beqz    $r15, .L_terminate_program      ! no _call_exit? go exit
        jral    $r15                            ! _call_exit will never return

.L_terminate_program:
        /* There are two ways to terminate program:
            1. User "syscall 0x1" directly.
            2. Call exit. The  return value $r0 from main() is
              implicitly passed as argument.

            Currently, we use option 2 as a solution to follow C99 5.1.2.2.3,
            but aware that general exit() will do some cleanup procedures
            which may result in large-memory-footprints.  */

        bal     exit

.L_forever_loop:
        /* Should never return here.  */
        b       .L_forever_loop

        .size   _start, .-_start