Created
December 5, 2016 01:04
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Simple utility calculating some basic heap chunk's characteristics like chunk size, bin index and it's range - according to original Doug Lea's heap allocator implementation. Useful while grasping Heap Overflow binning conditions.
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// vim: ai:si:ts=2:sw=2 | |
#include <stdio.h> | |
#define INTERNAL_SIZE_T size_t | |
#define SIZE_SZ sizeof(INTERNAL_SIZE_T) | |
#define MINSIZE 2*SIZE_SZ | |
#define MALLOC_ALIGNMENT ( SIZE_SZ + SIZE_SZ ) | |
#define MALLOC_ALIGN_MASK ( MALLOC_ALIGNMENT - 1 ) | |
#define request2size(req, nb) \ | |
((nb = (req) + (SIZE_SZ + MALLOC_ALIGN_MASK)),\ | |
((long)nb <= 0 || nb < (INTERNAL_SIZE_T) (req) \ | |
? (1) \ | |
: ((nb < (MINSIZE + MALLOC_ALIGN_MASK) \ | |
? (nb = MINSIZE) : (nb &= ~MALLOC_ALIGN_MASK)), 0))) | |
#define bin_index(sz) \ | |
((((unsigned long)(sz) >> 9) == 0) ? ((unsigned long)(sz) >> 3):\ | |
(((unsigned long)(sz) >> 9) <= 4) ? 56 + ((unsigned long)(sz) >> 6):\ | |
(((unsigned long)(sz) >> 9) <= 20) ? 91 + ((unsigned long)(sz) >> 9):\ | |
(((unsigned long)(sz) >> 9) <= 84) ? 110 + ((unsigned long)(sz) >> 12):\ | |
(((unsigned long)(sz) >> 9) <= 340) ? 119 + ((unsigned long)(sz) >> 15):\ | |
(((unsigned long)(sz) >> 9) <= 1364) ? 124 + ((unsigned long)(sz) >> 18):\ | |
126) | |
void bin_range(unsigned long sz, unsigned long *bmin, unsigned long *bmax) { | |
unsigned long d = (unsigned long)(sz) >> 9; | |
if( d == 0 ) *bmin = ((unsigned long)(sz >> 3) * (1 << 3)), *bmax = (*bmin + (1 << 3)); | |
else if( d <= 4 ) *bmin = ((unsigned long)(sz >> 6) * (1 << 6)), *bmax = (*bmin + (1 << 6)); | |
else if( d <= 20 ) *bmin = ((unsigned long)(sz >> 9) * (1 << 9)), *bmax = (*bmin + (1 << 9)); | |
else if( d <= 84 ) *bmin = ((unsigned long)(sz >> 12) * (1 << 12)), *bmax = (*bmin + (1 << 12)); | |
else if( d <= 340 ) *bmin = ((unsigned long)(sz >> 15) * (1 << 15)), *bmax = (*bmin + (1 << 15)); | |
else if( d <= 1364 ) *bmin = ((unsigned long)(sz >> 18) * (1 << 18)), *bmax = (*bmin + (1 << 18)); | |
else *bmin = 0, *bmax = 0; | |
} | |
int main( int argc, char **argv) { | |
if (argc != 2) { | |
printf("Usage: %s <size>\n", argv[0]); | |
return 0; | |
} | |
unsigned long size = atoi(argv[1]); | |
unsigned long nb, min, max; | |
request2size(size, nb); | |
bin_range(size, &min, &max); | |
printf("Request:\t%d\n" | |
"Size:\t\t%d\n" | |
"Bin index:\t%d (%d-%d)\n", | |
size, nb, bin_index(nb), min, max); | |
} |
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