############################################################################## # crt0.S -- CRX default start-up routine # # # # Copyright (c) 2004 National Semiconductor Corporation # # # # 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 is the start routine of your CRX program. # # It is linked with your application automatically. You can use # # this routine as a template and modify it to your needs, yet this # # file must be supplied for the compiler. # # It is assumed that the following symbols are defined in your linker # # script: __STACK_START, __ISTACK_START, __DATA_START, __DATA_END, # # __DATA_IMAGE_START, __BSS_START, __BSS_END. # ############################################################################## .text .align 4 .globl _main .globl _start .globl _atexit .globl _exit .globl __dispatch_table _start: #----------------------------------------------------------------------------# # Initialize the stack pointers. The constants __STACK_START and # # __ISTACK_START should be defined in the linker script. # movd $__STACK_START, sp movd $__ISTACK_START, r0 mtpr r0, isp #----------------------------------------------------------------------------# # Initialize the default sections according to the linker script. # movd $__DATA_END, r4 subd $__DATA_START, r4 movd $__DATA_START, r2 movd $__DATA_IMAGE_START, r3 bal ra, _memcpy movd $__BSS_END, r4 subd $__BSS_START, r4 movd $__BSS_START, r2 movd $0, r3 bal ra, _memset #----------------------------------------------------------------------------# # Initialize the intbase (pointer to the dispatch table). # movd $__dispatch_table, r0 mtpr r0, intbase #----------------------------------------------------------------------------# # Handle global and static constructurs execution and setup # # destructors to be called from exit. # bal ra, _init movd $_fini, r2 bal ra, _atexit #----------------------------------------------------------------------------# # Here you may add initializations that are specific to your # # environment. For example: # # 1. Configure wait states and other BIU parameters in order to get # # the best performance out of your target (see the specification # # document). # # 2. Enable maskable interrupts that should be enabled when your # # program starts to execute. # #----------------------------------------------------------------------------# # Jump to the main function in your application. # bal ra, _main #----------------------------------------------------------------------------# # Upon returning from the main function (if it isn't an infinite loop), # # jump to the exit function. The exit function is located in the # # library 'libc.a'. # movd r0, r2 # _main return value is passed as a # parameter to exit. br _exit # returns control to the debugger.