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[rdrand] add an untested workaround for i686 machine

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This commit is contained in:
Vincent Hanquez 2016-06-03 07:12:38 +01:00
parent 5cf7d08ca6
commit f5a811e755
1 changed files with 28 additions and 7 deletions
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35
cbits/cryptonite_rdrand.c
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@ -65,17 +65,38 @@ static inline int crypto_random_rdrand64_step(uint64_t *buffer)
: \ : \
: "cc") : "cc")
/* inline encoding of 'rdrand %eax' to cover old binutils
* - no inputs
* - 'cc' to the clobber list as we modify condition code.
* - output of rdrand in eax and have a 8 bit error condition
*/
#define inline_rdrand_eax(val, err) \
asm(".byte 0x0f,0xc7,0xf0; setc %1" \
: "=a" (val), "=q" (err) \
: \
: "cc")
#ifdef __x86_64__
# define RDRAND_SZ 8
# define RDRAND_T uint64_t
#define inline_rdrand(val, err) inline_rdrand_rax(val, err)
#else
# define RDRAND_SZ 4
# define RDRAND_T uint32_t
#define inline_rdrand(val, err) inline_rdrand_eax(val, err)
#endif
/* Returns the number of bytes succesfully generated */ /* Returns the number of bytes succesfully generated */
int cryptonite_get_rand_bytes(uint8_t *buffer, size_t len) int cryptonite_get_rand_bytes(uint8_t *buffer, size_t len)
{ {
uint64_t tmp; RDRAND_T tmp;
int aligned = (intptr_t) buffer % 8; int aligned = (intptr_t) buffer % RDRAND_SZ;
int orig_len = len; int orig_len = len;
int to_alignment = 8 - aligned; int to_alignment = RDRAND_SZ - aligned;
uint8_t ok; uint8_t ok;
if (aligned != 0) { if (aligned != 0) {
inline_rdrand_rax(tmp, ok); inline_rdrand(tmp, ok);
if (!ok) if (!ok)
return 0; return 0;
memcpy(buffer, (uint8_t *) &tmp, to_alignment); memcpy(buffer, (uint8_t *) &tmp, to_alignment);
@ -83,15 +104,15 @@ int cryptonite_get_rand_bytes(uint8_t *buffer, size_t len)
len -= to_alignment; len -= to_alignment;
} }
for (; len >= 8; buffer += 8, len -= 8) { for (; len >= RDRAND_SZ; buffer += RDRAND_SZ, len -= RDRAND_SZ) {
inline_rdrand_rax(tmp, ok); inline_rdrand(tmp, ok);
if (!ok) if (!ok)
return (orig_len - len); return (orig_len - len);
*((uint64_t *) buffer) = tmp; *((uint64_t *) buffer) = tmp;
} }
if (len > 0) { if (len > 0) {
inline_rdrand_rax(tmp, ok); inline_rdrand(tmp, ok);
if (!ok) if (!ok)
return (orig_len - len); return (orig_len - len);
memcpy(buffer, (uint8_t *) &tmp, len); memcpy(buffer, (uint8_t *) &tmp, len);