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/* Copyright (c) 2013 Nordic Semiconductor. All Rights Reserved.
*
* The information contained herein is property of Nordic Semiconductor ASA.
* Terms and conditions of usage are described in detail in NORDIC
* SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
*
* Licensees are granted free, non-transferable use of the information. NO
* WARRANTY of ANY KIND is provided. This heading must NOT be removed from
* the file.
*
*/
#include <stdint.h>
#include <string.h>
/**
* @brief Function for aborting current application/bootloader jump to to other app/bootloader.
*
* @details This functions will use the address provide to swap the stack pointer and then load
* the address of the reset handler to be executed. It will check current system mode
* (thread/handler) and if in thread mode it will reset into other application.
* If in handler mode \ref isr_abort will be executed to ensure correct exit of handler
* mode and jump into reset handler of other application.
*
* @param[in] start_addr Start address of other application. This address must point to the
initial stack pointer of the application.
*
* @note This function will never return but issue a reset into provided application.
*/
static inline void bootloader_util_reset (uint32_t start_addr) __attribute__ ((optimize("-fomit-frame-pointer")));
static inline void bootloader_util_reset(uint32_t start_addr)
{
__asm volatile(
"ldr r0, [%0]\t\n" // Get App initial MSP for bootloader.
"msr msp, r0\t\n" // Set the main stack pointer to the applications MSP.
"ldr r0, [%0, #0x04]\t\n" // Load Reset handler into R0.
"movs r4, #0xFF\t\n" // Move ones to R4.
"sxtb r4, r4\t\n" // Sign extend R4 to obtain 0xFFFFFFFF instead of 0xFF.
"mrs r5, IPSR\t\n" // Load IPSR to R5 to check for handler or thread mode.
"cmp r5, #0x00\t\n" // Compare, if 0 then we are in thread mode and can continue to reset handler of bootloader.
"bne isr_abort\t\n" // If not zero we need to exit current ISR and jump to reset handler of bootloader.
"mov lr, r4\t\n" // Clear the link register and set to ones to ensure no return.
"bx r0\t\n" // Branch to reset handler of bootloader.
"isr_abort: \t\n"
"mov r5, r4\t\n" // Fill with ones before jumping to reset handling. Will be popped as LR when exiting ISR. Ensures no return to application.
"mov r6, r0\t\n" // 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.
"movs r7, #0x21\t\n" // Move MSB reset value of xPSR to R7. Will be popped as xPSR when exiting ISR. xPSR is 0x21000000 thus MSB is 0x21.
"rev r7, r7\t\n" // Reverse byte order to put 0x21 as MSB.
"push {r4-r7}\t\n" // Push everything to new stack to allow interrupt handler to fetch it on exiting the ISR.
"movs r4, #0x00\t\n" // Fill with zeros before jumping to reset handling. We be popped as R0 when exiting ISR (Cleaning up of the registers).
"movs r5, #0x00\t\n" // Fill with zeros before jumping to reset handling. We be popped as R1 when exiting ISR (Cleaning up of the registers).
"movs r6, #0x00\t\n" // Fill with zeros before jumping to reset handling. We be popped as R2 when exiting ISR (Cleaning up of the registers).
"movs r7, #0x00\t\n" // Fill with zeros before jumping to reset handling. We be popped as R3 when exiting ISR (Cleaning up of the registers).
"push {r4-r7}\t\n" // Push zeros (R4-R7) to stack to prepare for exiting the interrupt routine.
"movs r0, #0xF9\t\n" // Move the execution return command into register, 0xFFFFFFF9.
"sxtb r0, r0\t\n" // Sign extend R0 to obtain 0xFFFFFFF9 instead of 0xF9.
"bx r0\t\n" // No return - Handler mode will be exited. Stack will be popped and execution will continue in reset handler initializing other application.
".align\t\n"
:: "r" (start_addr) // Argument list for the gcc assembly. start_addr is %0.
: "r0", "r4", "r5", "r6", "r7" // List of register maintained manually.
);
}
void bootloader_util_app_start(uint32_t start_addr)
{
bootloader_util_reset(start_addr);
}
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