我想通过将代码添加到{u-boot_sources}/arch/arm/cpu/armv7/omap-common/hwinit-common.c. U-boot 应在 PandaBoard ES (omap4460 SoC) 上使用。
因此，首先我在我的 x86 电脑上成功实现了代码，并将其移植到基于 ARM 的 PandaBoard。完整的代码可以在这里找到（作为旁注，“main”函数是 s_init()）：
但是，我预计会有几十个意想不到的效果，这会导致在代码执行期间停止、在读取 u-boot.img 后停止 u-boot 或根本不发送输出（因此不启动）。
例如，我想在一个-loop 中调用两个函数 ( computeSyndrome, ) ，它是另一个函数的一部分。decodeErrorsforgolayDecode
对于我的第一个问题，请忽略以/* >>>> These lines of code below totally break u-boot. 同样只有computeSyndrome与调用函数结合的函数golayDecode很重要。
问题：如果注释掉这两个功能computeSyndrome并且decodeErrors一切正常并且操作系统（Android）正在启动。但是，如果computeSyndrome未注释掉并因此得到处理，则 u-boot 在显示reading u-boot.img. 关于它的有趣之处在于：即使我computeSyndrome用一个不会迭代值或显示内容的虚假函数替换，u-boot 也会卡住。
此外，如果我删除下面的多行注释以还包含残留代码，则 u-boot 不会显示任何字符。(1*)
我是微处理器编程的初学者，但我根本无法弄清楚这 12 行 computeSyndrome 函数或 u-boot 的一般行为中可能存在的错误。(2*)
有人知道我错过了什么吗？
谢谢，P。
1* 我正在使用 minicom 显示 u-boot 的输出，我通过串行 USB 转换器接收到该输出。
2* 我使用以下编译器标志来确保编译时没有错误：-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]);
}