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Prevent building the HAVEGE module on platforms where it doesn't work

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If int is not capable of storing as many values as unsigned, the code
may generate a trap value. If signed int and unsigned int aren't
32-bit types, the code may calculate meaningless values.
This commit is contained in:
Gilles Peskine 2019-06-17 15:12:51 +02:00
parent 31a4ba7264
commit 04659a023e
1 changed files with 11 additions and 0 deletions
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11
library/havege.c
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@ -38,8 +38,19 @@
#include "mbedtls/timing.h"
#include "mbedtls/platform_util.h"
#include <limits.h>
#include <string.h>
/* If int isn't capable of storing 2^32 distinct values, the code of this
* module may cause a processor trap or a miscalculation. If int is more
* than 32 bits, the code may not calculate the intended values. */
#if INT_MIN + 1 != -0x7fffffff
#error "The HAVEGE module requires int to be exactly 32 bits, with INT_MIN = -2^31."
#endif
#if UINT_MAX != 0xffffffff
#error "The HAVEGE module requires unsigned to be exactly 32 bits."
#endif
/* ------------------------------------------------------------------------
* On average, one iteration accesses two 8-word blocks in the havege WALK
* table, and generates 16 words in the RES array.