2 * Copyright (c) 2012 Alex Hornung <alex@alexhornung.com>.
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30 #include <machine/asmacros.h>
34 /* int rdrand_rng(uint8_t *out, int limit) */
37 shrl $3, %ecx /* Divide by 8 to get 64-bit word count */
42 * rdx: (output) entropy
44 rdrand %rdx /* rdrand64 */
47 * The carry flag (CF) determines if the instruction was
50 * CF = 0: Random value not available at time of execution.
55 * The operation was successful, so store the random data
56 * from the register into our buffer.
61 * Increment the count of stored random words as well as the
62 * buffer pointer in rdi.
68 * If we haven't already read enough random words,
74 /* return the number of stored random bytes (random words * 8) */