On Tuesday 26 May 2009 20:50:56 Nathan Wharton wrote:

I added the following patch:

--- batmand-r1269/batman/allocate.c 2009-05-20 13:54:18.000000000 -0500 +++ batmand-r1269.mod/batman/allocate.c 2009-05-26 12:25:07.000000000 -0500 @@ -206,6 +206,10 @@ struct chunkHeader *chunkHeader; struct chunkTrailer *chunkTrailer; unsigned char *chunk;

•   uint32_t remainder = length % 4;
  

•   if (remainder > 0)
  

•     length += 4 - remainder;
  
  

/* printf("sizeof(struct chunkHeader) = %u, sizeof (struct chunkTrailer) = %u\n", sizeof (struct chunkHeader), sizeof (struct chunkTrailer)); */

Please don't introduce more magic numbers. If you need an alignment on integer granularity then please use sizeof(int) instead of a simple constant. The rest looks quite good and logical. I assumed that the only architecture without automatic catching of alignment problems is mips with load operators to the fp registers (never had such problems on simple arm machine nor could I produce that problem on them). Is there any other documentation about such problems on xscale or can you proof this with an test program (malloc 6 byte, write uint32_t to first 4 byte, write another uint32_t to byte 2-5, compare bytes with input - don't forget to set it volatile)? Your current proof if concept test only shows that the "overriden" bytes will not get overriden after moving them some bytes higher.

========================================= #include <stdio.h> #include <stdlib.h>

#define x_moved(pos) ((int*)&x[pos])[0] static const int value1 = 0x01234567; static const int value2 = 0x89abcdef;

int main() { volatile char *x = (char*)malloc(sizeof(int) * 2); x_moved(0) = value1; x_moved(2) = value2;

if (x_moved(2) != value2) { printf("ERROR Value: "); } else { printf("Value: "); } printf("%x %x\n", x_moved(0) , x_moved(2));

free(x); return 0; } =========================================

Best regards, Sven