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) */
39 shrl $2, %ecx /* Divide by 4 to get 32-bit word count */
44 * edx: (output) entropy
46 rdrand %edx /* rdrand32 */
49 * The carry flag (CF) determines if the instruction was
52 * CF = 0: Random value not available at time of execution.
57 * The operation was successful, so store the random data
58 * from the register into our buffer.
63 * Increment the count of stored random words as well as the
64 * buffer pointer in edi.
70 * If we haven't already read enough random words,
76 /* return the number of stored random bytes (random words * 4) */