rdrand.c

#include <stdio.h>
#include <stdint.h>

int rdrand(uint32_t *out) {
    char rc;
    unsigned int val;

    __asm__ volatile(
        "rdrand %0 ; setc %1"
        : "=r" (val), "=qm" (rc)
        :
        : "cc"
    );

    if (rc) {
        *out = val;
    } else {
        *out = 0;
    }

    return rc;
}

int rdseed(uint32_t *out) {
    char rc;
    unsigned int val;

    __asm__ volatile(
        "rdseed %0 ; setc %1"
        : "=r" (val), "=qm" (rc)
        :
        : "cc"
    );

    if (rc) {
        *out = val;
    } else {
        *out = 0;
    }

    return rc;
}

int main(int argc, char *argv[])
{
    int failures = 0;
    for (int j, i = 0; i < 2000; ++i) {
        for (j = 0; j < 10; ++j) {
            uint32_t val = 0;
            if (rdrand(&val)) {
                printf("RDRAND() = 0x%08x\n", val);
                break;
            } else {
                failures++;
            }
        }
        if (j == 10) {
            puts("RDRAND() = FAIL");
            return 1;
        }
    }
    printf("RDRAND: %d failures\n", failures);

    /*
    failures = 0;
    for (int j, i = 0; i < 2000; ++i) {
        for (j = 0; j < 10; ++j) {
            uint32_t val = 0;
            if (rdseed(&val)) {
                printf("RDSEED() = 0x%08x\n", val);
                break;
            } else {
                failures++;
            }
        }
        if (j == 10) {
            puts("RDSEED() = FAIL");
            return 1;
        }
    }
    printf("RDSEED: %d failures\n", failures);
    */

    return 0;
}