bootloader_util_arm.c

00001 /* Copyright (c) 2013 Nordic Semiconductor. All Rights Reserved.
00002  *
00003  * The information contained herein is property of Nordic Semiconductor ASA.
00004  * Terms and conditions of usage are described in detail in NORDIC
00005  * SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
00006  *
00007  * Licensees are granted free, non-transferable use of the information. NO
00008  * WARRANTY of ANY KIND is provided. This heading must NOT be removed from
00009  * the file.
00010  *
00011  */
00012 
00013 #include "bootloader_util.h "
00014 #include <stdint.h>
00015 
00016 
00017 /**
00018  * @brief Function for aborting current handler mode and jump to to other application/bootloader.
00019  *
00020  * @details This functions will use the address provide (reset handler) to be executed after 
00021  *          handler mode is exited. It creates an initial stack to ensure correct reset behavior 
00022  *          when the reset handler is executed.
00023  *
00024  * @param[in]  reset_handler  Address of the reset handler to be executed when handler mode exits.
00025  *
00026  * @note This function must never be called directly from 'C' but is intended only to be used from 
00027  *       \ref bootloader_util_reset. This function will never return but issue a reset into 
00028  *       provided address.
00029  */
00030 __asm void isr_abort(uint32_t reset_handler)
00031 {
00032 xPSR_RESET      EQU 0x21000000  ; Default value of xPSR after System Reset.
00033 EXC_RETURN_CMD  EQU 0xFFFFFFF9  ; EXC_RETURN for ARM Cortex. When loaded to PC the current interrupt service routine (handler mode) willl exit and the stack will be popped. Execution will continue in thread mode.
00034 
00035     LDR   R4,=MASK_ONES         ; Fill with ones before jumping to reset handling. We be popped as R12 when exiting ISR (Cleaning up the registers).
00036     LDR   R5,=MASK_ONES         ; Fill with ones before jumping to reset handling. We be popped as LR when exiting ISR. Ensures no return to application.
00037     MOV   R6, R0                ; Move address of reset handler to R6. Will be popped as PC when exiting ISR. Ensures the reset handler will be executed when exist ISR.
00038     LDR   R7,=xPSR_RESET        ; Move reset value of xPSR to R7. Will be popped as xPSR when exiting ISR.
00039     PUSH  {r4-r7}               ; Push everything to new stack to allow interrupt handler to fetch it on exiting the ISR.
00040     
00041     LDR   R4,=MASK_ZEROS        ; Fill with zeros before jumping to reset handling. We be popped as R0 when exiting ISR (Cleaning up of the registers).
00042     LDR   R5,=MASK_ZEROS        ; Fill with zeros before jumping to reset handling. We be popped as R1 when exiting ISR (Cleaning up of the registers).
00043     LDR   R6,=MASK_ZEROS        ; Fill with zeros before jumping to reset handling. We be popped as R2 when exiting ISR (Cleaning up of the registers).
00044     LDR   R7,=MASK_ZEROS        ; Fill with zeros before jumping to reset handling. We be popped as R3 when exiting ISR (Cleaning up of the registers).
00045     PUSH  {r4-r7}               ; Push zeros (R4-R7) to stack to prepare for exiting the interrupt routine.
00046     
00047     LDR   R0,=EXC_RETURN_CMD    ; Load the execution return command into register.
00048     BX    R0                    ; No return - Handler mode will be exited. Stack will be popped and execution will continue in reset handler initializing other application.
00049     ALIGN
00050 }
00051 
00052 
00053 /**
00054  * @brief Function for aborting current application/bootloader jump to to other app/bootloader.
00055  *
00056  * @details This functions will use the address provide to swap the stack pointer and then load 
00057  *          the address of the reset handler to be executed. It will check current system mode 
00058  *          (thread/handler) and if in thread mode it will reset into other application.
00059  *          If in handler mode \ref isr_abort will be executed to ensure correct exit of handler 
00060  *          mode and jump into reset handler of other application.
00061  *
00062  * @param[in]  start_addr  Start address of other application. This address must point to the 
00063                initial stack pointer of the application.
00064  *
00065  * @note This function will never return but issue a reset into provided application.
00066  */
00067 __asm static void bootloader_util_reset(uint32_t start_addr)
00068 {
00069 MASK_ONES       EQU 0xFFFFFFFF  ; Ones, to be loaded into register as default value before reset.
00070 MASK_ZEROS      EQU 0x00000000  ; Zeros, to be loaded into register as default value before reset.
00071 
00072     LDR   R1, [R0]              ; Get App initial MSP for bootloader.
00073     MSR   MSP, R1               ; Set the main stack pointer to the applications MSP.
00074     LDR   R0,[R0, #0x04]        ; Load Reset handler into register 0.
00075     
00076     LDR   R2, =MASK_ZEROS       ; Load zeros to R2
00077     MRS   R3, IPSR              ; Load IPSR to R3 to check for handler or thread mode 
00078     CMP   R2, R3                ; Compare, if 0 then we are in thread mode and can continue to reset handler of bootloader
00079     BNE   isr_abort             ; If not zero we need to exit current ISR and jump to reset handler of bootloader
00080 
00081     LDR   R4, =MASK_ONES        ; Load ones to R4 to be placed in Link Register.
00082     MOV   LR, R4                ; Clear the link register and set to ones to ensure no return.
00083     BX    R0                    ; Branch to reset handler of bootloader
00084     ALIGN
00085 }
00086 
00087 
00088 void bootloader_util_app_start(uint32_t start_addr)
00089 {
00090     bootloader_util_reset(start_addr);
00091 }