[U-Boot] Unexpected effects/problems porting code to u-boot SPL

[bin4ry <0xbin4ry@gmail.com>]

I want to extend the u-boot SPL code with some fuzzy extractor logic by
adding code into
`{u-boot_sources}/arch/arm/cpu/armv7/omap-common/hwinit-common.c`.
U-boot shall be used on a PandaBoard ES (omap4460 SoC).

Thus, first I successfully implemented the code on my x86 pc and I am
porting it to the ARM-based PandaBoard. The complete code can be found
here (as a side note the "main" function is s_init()):

http://pastebin.com/iaz13Yn9

However, I am expecting dozens of unexptected effects, which results in
either stopping during the execution of the code, stopping u-boot after
reading u-boot.img or not sending output (and thus not booting) at all.

For example, I want to call two functions (`computeSyndrome`,
`decodeErrors`) inside a `for`-loop, which is part of another function
`golayDecode`.

For my first problem please ignore the code below the multiline comment
starting with `/*        >>>> These lines of code below totally break
u-boot`. Also only the function `computeSyndrome` in conjunction with
the calling function `golayDecode` is important.

The issue: If comment out both functions `computeSyndrome` and
`decodeErrors` everything works fine and the OS (Android) is booting.
However, if `computeSyndrome` is not commented out and thus gets
processed, u-boot stucks after displaying `reading u-boot.img`.
The funny thing about it: even if I replace `computeSyndrome` with a
bogus function which does not but iterating a values or displaying
stuff, u-boot stucks as well.

Furthermore, if I remove the multiline comment furhter below to also
include the residual code, u-boot doesn't display ony character. *

I am a beginner regarding microprocessor programming but I can not
figure out a possible error in these 12 lines of the computeSyndrome
function or the general behaviour of u-boot at all. **

Does anyone have a clue what I am missing?

Thanks,
P.

* I am using minicom to display the output of u-boot, which I receive
over serial-usb-converter.  
** I am using the following compiler flags to make sure there are no
errors at compile time: `-Wall -Wstrict-prototypes
-Wdisabled-optimization -W -pedantic`


    void golayDecode(volatile int x[12], volatile int y[12], volatile
unsigned int golayEncodedSecret[30], volatile unsigned int s, volatile
unsigned char repetitionDecodedSecretBits[360]){
    
    printf("\n[I] - Performing Golay decoding\r\n");
    volatile unsigned char secret[22] = {0};
    volatile unsigned char currentByte = 0, tmpByte = 0;
    volatile unsigned int golayDecodedSecret[30] ={0};
    volatile int twelveBitCounter = 0;//, j = 0, k = 0, q = 0, aux = 0,
found = 0, bitCounter = 0, i_2 = 7, currentSecretEncByte = 0x00;
    volatile int c_hat[2] = {0}, e[2] = {0};
    e[0] = s;
    e[1] = 0;

    for(twelveBitCounter = 0; twelveBitCounter < 30; twelveBitCounter+=2){
        printf("Computing syndrome and decoding errors for bytes %03x &
%03x\n", golayEncodedSecret[twelveBitCounter],
golayEncodedSecret[twelveBitCounter+1]);
          computeSyndrome(golayEncodedSecret[twelveBitCounter],
golayEncodedSecret[twelveBitCounter+1], x, y, s);
          decodeErrors(golayEncodedSecret[i], golayEncodedSecret[i+1],
x, y, s);
    }
    
    printf("\n[D] - Reconstructing secret bytes\r\n");

    
    /*        >>>> These lines of code below totally break u-boot
    for(i = 0; i < 30; i+=2){
        currentSecretEncByte = golayDecodedSecret[i];
        volatile int j = 11;

        // Access each source bit        
        for(; 0<=j; j--){            
            volatile int currentSourceBit = (currentSecretEncByte >> j)
& 0x01;    
        
            repetitionDecodedSecretBits[bitCounter] = currentSourceBit;
            bitCounter++;
        }
    }
    
    k = 0;
    for(i = 0; i<176; i++){
        tmpByte =  repetitionDecodedSecretBits[i] << i_2;
        currentByte = currentByte | tmpByte;
        i_2--;
        if(i_2==0){    // We collected 8 bits and created a byte
            secret[k] = currentByte;
            i_2 = 7;
            tmpByte = 0x00;
            currentByte = 0x00;
            k++;
        }        
    }

    SHA256_CTX ctx;
    unsigned char hash[32];

    printf("\n[I] - Generating secret key K\n");
    sha256_init(&ctx);
    sha256_update(&ctx,secret,strlen((const char*)secret));
    sha256_final(&ctx,hash);

    printf("\n[I] - This is our secret key
K\n\t==================================\n\t");
    print_hash(hash);
    printf("\t==================================\n");
    */
    }


    /* Function for syndrome computation */
    void computeSyndrome(int r0, int r1, volatile int x[12], volatile
int y[12], volatile unsigned int s){
    unsigned int syndromeBitCounter, syndromeMatrixCounter, syndromeAux;

    s = 0;
    for(syndromeMatrixCounter=0; syndromeMatrixCounter<12;
syndromeMatrixCounter++){
        syndromeAux = 0;
        
        for(syndromeBitCounter=0; syndromeBitCounter<12;
syndromeBitCounter++){
            syndromeAux =
syndromeAux^((x[syndromeMatrixCounter]&r0)>>syndromeBitCounter &0x01);
        }
        for(syndromeBitCounter=0; syndromeBitCounter<12;
syndromeBitCounter++){
            syndromeAux =
syndromeAux^((y[syndromeMatrixCounter]&r1)>>syndromeBitCounter &0x01);
        }
        s = (s<<1)^syndromeAux;
        
    }
    }



    /* Funcion to recover original byte */
    void decodeErrors(int r0, int r1, volatile int x[12], volatile int
y[12], volatile unsigned int s){
    //printf("\n[D] - Starting to decode errors for %3x | %3x\n", r0, r1);
    volatile unsigned int c_hat[2] = {0xaa}, e[2] = {0xaa};
    volatile unsigned int q;
    unsigned int i, j, aux, found;

    //printf("Step 2\n");
    if(weight(s)<=3){
        e[0] = s;
        e[1] = 0;
    }else{
        /******* STEP 3 */
        //printf("Step 3\n");
        i = 0;
        found = 0;
        do{
            if (weight(s^y[i]) <=2){
                     e[0] = s^y[i];
                     e[1] = x[i];
                     found = 1;
                printf("\ntest 2\n");
               }
             i++;
            }while ((i<12) && (!found));

            if (( i==12 ) && (!found)){
               /******* STEP 4 */
              //printf("Step 4\n");
               q = 0;
               for (j=0; j<12; j++){
                      aux = 0;
                       for (i=0; i<12; i++)
                     aux = aux ^ ( (y[j]&s)>>i & 0x01 );
                       q = (q<<1) ^ aux;
                 }

               /******* STEP 5 */
               //printf("Step 5\n");
               if (weight(q) <=3){
                       e[0] = 0;
                       e[1] = q;
                }else{
                       /******* STEP 6 */
                       //printf("Step 6\n");
                       i = 0;
                       found = 0;
                       do{
                     if (weight(q^y[i]) <=2){
                             e[0] = x[i];
                             e[1] = q^y[i];
                             found = 1;
                       }
                     i++;
                }while((i<12) && (!found));
           
                       if ((i==12) && (!found)){
                       /******* STEP 7 */
                       printf("\n[E] - uncorrectable error pattern! (%3x
| %3x)\n", r0, r1);
                       /* You can raise a flag here, or output the
vector as is */
                       //exit(1);
                }
            }
         }
    }

    c_hat[0] = r0^e[0];
    c_hat[1] = r1^e[1];
    //printf("\t\tEstimated codeword = %x%x\n", c_hat[0], c_hat[1]);
    }