/*

 * Copyright (C) Thomas DuBuisson

 * Copyright (C) 2013 Vincent Hanquez <tab@snarc.org>

 *

 * All rights reserved.

 * 

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the author nor the names of his contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 * 

 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

#include <stdint.h>

#include <stdlib.h>

#include <stdio.h>

#include <string.h>

int cryptonite_cpu_has_rdrand()

{

	uint32_t ax,bx,cx,dx,func=1;

#if defined(__PIC__) && defined(__i386__)

	__asm__ volatile ("mov %%ebx, %%edi;" "cpuid;" "xchgl %%ebx, %%edi;"

		: "=a" (ax), "=D" (bx), "=c" (cx), "=d" (dx) : "a" (func));

#else

	__asm__ volatile ("cpuid": "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));

#endif

	return (cx & 0x40000000);

}

/* inline encoding of 'rdrand %rax' to cover old binutils

 * - no inputs

 * - 'cc' to the clobber list as we modify condition code.

 * - output of rdrand in rax and have a 8 bit error condition

 */

#define inline_rdrand_rax(val, err) \

	asm(".byte 0x48,0x0f,0xc7,0xf0; setc %1" \

	   : "=a" (val), "=q" (err) \

	   : \

	   : "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) err = cryptonite_rdrand_step(&val)

#else

# define RDRAND_SZ 4

# define RDRAND_T  uint32_t

#define inline_rdrand(val, err) err = cryptonite_rdrand_step(&val)

#endif

/* sadly many people are still using an old binutils,

 * leading to report that instruction is not recognized.

 */

#if 1

/* Returns 1 on success */

static inline int cryptonite_rdrand_step(RDRAND_T *buffer)

{

	unsigned char err;

	asm volatile ("rdrand %0; setc %1" : "=r" (*buffer), "=qm" (err));

	return (int) err;

}

#endif

/* Returns the number of bytes succesfully generated */

int cryptonite_get_rand_bytes(uint8_t *buffer, size_t len)

{

	RDRAND_T tmp;

	int aligned = (intptr_t) buffer % RDRAND_SZ;

	int orig_len = len;

	int to_alignment = RDRAND_SZ - aligned;

	uint8_t ok;

	if (aligned != 0) {

		inline_rdrand(tmp, ok);

		if (!ok)

			return 0;

		memcpy(buffer, (uint8_t *) &tmp, to_alignment);

		buffer += to_alignment;

		len -= to_alignment;

	}

	for (; len >= RDRAND_SZ; buffer += RDRAND_SZ, len -= RDRAND_SZ) {

		inline_rdrand(tmp, ok);

		if (!ok)

			return (orig_len - len);

		*((RDRAND_T *) buffer) = tmp;

	}

	if (len > 0) {

		inline_rdrand(tmp, ok);

		if (!ok)

			return (orig_len - len);

		memcpy(buffer, (uint8_t *) &tmp, len);

	}

	return orig_len;

}