IAP on LPC 1768

Question

I am trying to use IAP (in application programming) to copy the code of a function from one point in memory space to another (I know this doesn't have any use, but this is absolutely crucial for a project that I'm working on). The copying of the code seems to work with out a hitch, but when I call the copied function it always results in hardfaults. The function I'm copying doesn't have any references to other functions or data (It is a simple return function), so there is no problem of relative address errors. I've given my code below along with the output that I get.

#include "mbed.h"
#include "IAP.h"

#define TARGET_SECTOR       14


char code[1024];
IAP     iap;
char val = 0;


typedef int (*function) ();
function blinkfunction;

MPU_Type mpu;


extern "C"
void HardFault_Handler() {
    register unsigned int _msp __asm("msp");
    printf("Hard Fault! %x (%x)\r\n", SCB->HFSR, *((unsigned int *)(_msp + 24)));
    printf("HFSR: 0x%X\n\r", SCB->HFSR);
    printf("MMFAR: 0x%X\tMMFSR: 0x%X\n\r", SCB->MMFAR, SCB->CFSR);
    printf("BFAR: 0x%X\tBFSR: 0x%X\n\r", SCB->BFAR, SCB->CFSR);
    printf(" - %x\r\n", (*(volatile uint32_t*)0xe000ed24));
//    printf("Hard Fault! %x\r\n", SCB->HFSR);

        printf("*********** MPU Settings *************\n\r");
        printf("TYPE: 0x%X\n\r", mpu.TYPE);
        printf("CTRL: 0x%X\n\r", mpu.CTRL);
    exit(-1);
}




int blink() {
    int a = 1, b = 1;
    return a + b;
}



void copy_code_ram() {

    char *charptr;

    charptr = (char *)&blink;
    int i;
    for(i = 0; i <200 ; i++) {
        code[i] = *charptr;
        charptr++;
    }
}    



void print_function(char *ptr, int num) {
    for(; num > 0; num--) {
        printf("0x%X  ", *ptr);
        ptr++;
    }
}


int main() {
    int r;

    printf("blink code:\n");
    print_function((char *)&blink, 100);


    printf("\n\r\n\r\n\r");
    copy_code_ram();

    //Print sector  
    print_function(sector_start_adress[TARGET_SECTOR], 100);
    printf("\n\r\n\r\n\r");

    iap.prepare( TARGET_SECTOR, TARGET_SECTOR);
    iap.erase (TARGET_SECTOR, TARGET_SECTOR);
    iap.prepare( TARGET_SECTOR, TARGET_SECTOR);
    r   = iap.write( code, sector_start_adress[TARGET_SECTOR], 256);

    printf("\n\r\n\r\n\r");
    printf( "copied: SRAM(0x%08X)->Flash(0x%08X) for %d bytes. (result=0x%08X)\r\n", code, sector_start_adress[ TARGET_SECTOR ], 1024, r );
    printf("\n\r\n\r\n\r");

    blinkfunction = (function) (sector_start_adress[TARGET_SECTOR]);

    printf("\n\r\n\r\n\r");
        print_function((char *)blinkfunction, 100);

    r = 0;
    r = blink();
    printf("The return value from blink is %d\n\r", r);

    r = blinkfunction();
    printf("The return value from blinkfunction is %d\n\r", r);

    while(1) {


    }
}

Here is the output:

Hard Fault! 4000000 (e000)
HFSR: 0x400000000
MMFAR: 0xE000ED34  MMFSR: 0x20000
BFAR: 0xE000ED38   BFSR: 0x20000

I think I'm doing something wrong in calling the function. Can someone please point out my mistake?

Thanks

Answer 1

You forgot to set the thumb bit in the function address:

blinkfunction = (function) (sector_start_adress[TARGET_SECTOR] | 1);

The compiler knows to set this in most cases, but it not in a direct cast to a function pointer.