[mirror_ubuntu-artful-kernel.git] / lib / mpi / mpicoder.c

/* mpicoder.c  -  Coder for the external representation of MPIs
 * Copyright (C) 1998, 1999 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <linux/bitops.h>
#include <linux/count_zeros.h>
#include <linux/byteorder/generic.h>
#include <linux/string.h>
#include "mpi-internal.h"

#define MAX_EXTERN_MPI_BITS 16384

/**
 * mpi_read_raw_data - Read a raw byte stream as a positive integer
 * @xbuffer: The data to read
 * @nbytes: The amount of data to read
 */
MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
{
	const uint8_t *buffer = xbuffer;
	int i, j;
	unsigned nbits, nlimbs;
	mpi_limb_t a;
	MPI val = NULL;

	while (nbytes > 0 && buffer[0] == 0) {
		buffer++;
		nbytes--;
	}

	nbits = nbytes * 8;
	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		return NULL;
	}
	if (nbytes > 0)
		nbits -= count_leading_zeros(buffer[0]);
	else
		nbits = 0;

	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	val = mpi_alloc(nlimbs);
	if (!val)
		return NULL;
	val->nbits = nbits;
	val->sign = 0;
	val->nlimbs = nlimbs;

	if (nbytes > 0) {
		i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
		i %= BYTES_PER_MPI_LIMB;
		for (j = nlimbs; j > 0; j--) {
			a = 0;
			for (; i < BYTES_PER_MPI_LIMB; i++) {
				a <<= 8;
				a |= *buffer++;
			}
			i = 0;
			val->d[j - 1] = a;
		}
	}
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_raw_data);

MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
{
	const uint8_t *buffer = xbuffer;
	int i, j;
	unsigned nbits, nbytes, nlimbs, nread = 0;
	mpi_limb_t a;
	MPI val = NULL;

	if (*ret_nread < 2)
		goto leave;
	nbits = buffer[0] << 8 | buffer[1];

	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		goto leave;
	}
	buffer += 2;
	nread = 2;

	nbytes = DIV_ROUND_UP(nbits, 8);
	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	val = mpi_alloc(nlimbs);
	if (!val)
		return NULL;
	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	i %= BYTES_PER_MPI_LIMB;
	val->nbits = nbits;
	j = val->nlimbs = nlimbs;
	val->sign = 0;
	for (; j > 0; j--) {
		a = 0;
		for (; i < BYTES_PER_MPI_LIMB; i++) {
			if (++nread > *ret_nread) {
				printk
				    ("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
				     nread, *ret_nread);
				goto leave;
			}
			a <<= 8;
			a |= *buffer++;
		}
		i = 0;
		val->d[j - 1] = a;
	}

leave:
	*ret_nread = nread;
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_from_buffer);

static int count_lzeros(MPI a)
{
	mpi_limb_t alimb;
	int i, lzeros = 0;

	for (i = a->nlimbs - 1; i >= 0; i--) {
		alimb = a->d[i];
		if (alimb == 0) {
			lzeros += sizeof(mpi_limb_t);
		} else {
			lzeros += count_leading_zeros(alimb) / 8;
			break;
		}
	}
	return lzeros;
}

/**
 * mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
 *
 * @a:		a multi precision integer
 * @buf:	bufer to which the output will be written to. Needs to be at
 *		leaset mpi_get_size(a) long.
 * @buf_len:	size of the buf.
 * @nbytes:	receives the actual length of the data written on success and
 *		the data to-be-written on -EOVERFLOW in case buf_len was too
 *		small.
 * @sign:	if not NULL, it will be set to the sign of a.
 *
 * Return:	0 on success or error code in case of error
 */
int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
		    int *sign)
{
	uint8_t *p;
#if BYTES_PER_MPI_LIMB == 4
	__be32 alimb;
#elif BYTES_PER_MPI_LIMB == 8
	__be64 alimb;
#else
#error please implement for this limb size.
#endif
	unsigned int n = mpi_get_size(a);
	int i, lzeros;

	if (!buf || !nbytes)
		return -EINVAL;

	if (sign)
		*sign = a->sign;

	lzeros = count_lzeros(a);

	if (buf_len < n - lzeros) {
		*nbytes = n - lzeros;
		return -EOVERFLOW;
	}

	p = buf;
	*nbytes = n - lzeros;

	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
			lzeros %= BYTES_PER_MPI_LIMB;
		i >= 0; i--) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = cpu_to_be32(a->d[i]);
#elif BYTES_PER_MPI_LIMB == 8
		alimb = cpu_to_be64(a->d[i]);
#else
#error please implement for this limb size.
#endif
		memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);
		p += BYTES_PER_MPI_LIMB - lzeros;
		lzeros = 0;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_read_buffer);

/*
 * mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
 * Caller must free the return string.
 * This function does return a 0 byte buffer with nbytes set to zero if the
 * value of A is zero.
 *
 * @a:		a multi precision integer.
 * @nbytes:	receives the length of this buffer.
 * @sign:	if not NULL, it will be set to the sign of the a.
 *
 * Return:	Pointer to MPI buffer or NULL on error
 */
void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
{
	uint8_t *buf;
	unsigned int n;
	int ret;

	if (!nbytes)
		return NULL;

	n = mpi_get_size(a);

	if (!n)
		n++;

	buf = kmalloc(n, GFP_KERNEL);

	if (!buf)
		return NULL;

	ret = mpi_read_buffer(a, buf, n, nbytes, sign);

	if (ret) {
		kfree(buf);
		return NULL;
	}
	return buf;
}
EXPORT_SYMBOL_GPL(mpi_get_buffer);

/**
 * mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
 *
 * This function works in the same way as the mpi_read_buffer, but it
 * takes an sgl instead of u8 * buf.
 *
 * @a:		a multi precision integer
 * @sgl:	scatterlist to write to. Needs to be at least
 *		mpi_get_size(a) long.
 * @nbytes:	in/out param - it has the be set to the maximum number of
 *		bytes that can be written to sgl. This has to be at least
 *		the size of the integer a. On return it receives the actual
 *		length of the data written on success or the data that would
 *		be written if buffer was too small.
 * @sign:	if not NULL, it will be set to the sign of a.
 *
 * Return:	0 on success or error code in case of error
 */
int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned *nbytes,
		     int *sign)
{
	u8 *p, *p2;
#if BYTES_PER_MPI_LIMB == 4
	__be32 alimb;
#elif BYTES_PER_MPI_LIMB == 8
	__be64 alimb;
#else
#error please implement for this limb size.
#endif
	unsigned int n = mpi_get_size(a);
	int i, x, y = 0, lzeros, buf_len;

	if (!nbytes)
		return -EINVAL;

	if (sign)
		*sign = a->sign;

	lzeros = count_lzeros(a);

	if (*nbytes < n - lzeros) {
		*nbytes = n - lzeros;
		return -EOVERFLOW;
	}

	*nbytes = n - lzeros;
	buf_len = sgl->length;
	p2 = sg_virt(sgl);

	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
			lzeros %= BYTES_PER_MPI_LIMB;
		i >= 0; i--) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = cpu_to_be32(a->d[i]);
#elif BYTES_PER_MPI_LIMB == 8
		alimb = cpu_to_be64(a->d[i]);
#else
#error please implement for this limb size.
#endif
		if (lzeros) {
			y = lzeros;
			lzeros = 0;
		}

		p = (u8 *)&alimb + y;

		for (x = 0; x < sizeof(alimb) - y; x++) {
			if (!buf_len) {
				sgl = sg_next(sgl);
				if (!sgl)
					return -EINVAL;
				buf_len = sgl->length;
				p2 = sg_virt(sgl);
			}
			*p2++ = *p++;
			buf_len--;
		}
		y = 0;
	}
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_write_to_sgl);

/*
 * mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
 *			     data from the sgl
 *
 * This function works in the same way as the mpi_read_raw_data, but it
 * takes an sgl instead of void * buffer. i.e. it allocates
 * a new MPI and reads the content of the sgl to the MPI.
 *
 * @sgl:	scatterlist to read from
 * @nbytes:	number of bytes to read
 *
 * Return:	Pointer to a new MPI or NULL on error
 */
MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
{
	struct scatterlist *sg;
	int x, i, j, z, lzeros, ents;
	unsigned int nbits, nlimbs;
	mpi_limb_t a;
	MPI val = NULL;

	lzeros = 0;
	ents = sg_nents(sgl);

	for_each_sg(sgl, sg, ents, i) {
		const u8 *buff = sg_virt(sg);
		int len = sg->length;

		while (len && !*buff) {
			lzeros++;
			len--;
			buff++;
		}

		if (len && *buff)
			break;

		ents--;
		nbytes -= lzeros;
		lzeros = 0;
	}

	sgl = sg;
	nbytes -= lzeros;
	nbits = nbytes * 8;
	if (nbits > MAX_EXTERN_MPI_BITS) {
		pr_info("MPI: mpi too large (%u bits)\n", nbits);
		return NULL;
	}

	if (nbytes > 0)
		nbits -= count_leading_zeros(*(u8 *)(sg_virt(sgl) + lzeros)) -
			(BITS_PER_LONG - 8);

	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	val = mpi_alloc(nlimbs);
	if (!val)
		return NULL;

	val->nbits = nbits;
	val->sign = 0;
	val->nlimbs = nlimbs;

	if (nbytes == 0)
		return val;

	j = nlimbs - 1;
	a = 0;
	z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	z %= BYTES_PER_MPI_LIMB;

	for_each_sg(sgl, sg, ents, i) {
		const u8 *buffer = sg_virt(sg) + lzeros;
		int len = sg->length - lzeros;

		for (x = 0; x < len; x++) {
			a <<= 8;
			a |= *buffer++;
			if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
				val->d[j--] = a;
				a = 0;
			}
		}
		z += x;
		lzeros = 0;
	}
	return val;
}
EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);
Commit	Line	Data
cdec9cb5 DK	1	/* mpicoder.c - Coder for the external representation of MPIs
	2	* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
	3	*
	4	* This file is part of GnuPG.
	5	*
	6	* GnuPG is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (at your option) any later version.
	10	*
	11	* GnuPG is distributed in the hope that it will be useful,
	12	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	* GNU General Public License for more details.
	15	*
	16	* You should have received a copy of the GNU General Public License
	17	* along with this program; if not, write to the Free Software
	18	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
	19	*/
	20
e1045992	21	#include <linux/bitops.h>
a1164a3a	22	#include <linux/count_zeros.h>
d7552906	23	#include <linux/byteorder/generic.h>
90f864e2	24	#include <linux/string.h>
cdec9cb5 DK	25	#include "mpi-internal.h"
cdec9cb5 DK	26
cdec9cb5 DK	27	#define MAX_EXTERN_MPI_BITS 16384
cdec9cb5 DK	28
e1045992 DH	29	/**
	30	* mpi_read_raw_data - Read a raw byte stream as a positive integer
	31	* @xbuffer: The data to read
	32	* @nbytes: The amount of data to read
	33	*/
	34	MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
	35	{
	36	const uint8_t *buffer = xbuffer;
	37	int i, j;
	38	unsigned nbits, nlimbs;
	39	mpi_limb_t a;
	40	MPI val = NULL;
	41
5402b804	42	while (nbytes > 0 && buffer[0] == 0) {
e1045992 DH	43	buffer++;
	44	nbytes--;
	45	}
	46
	47	nbits = nbytes * 8;
	48	if (nbits > MAX_EXTERN_MPI_BITS) {
	49	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	50	return NULL;
	51	}
	52	if (nbytes > 0)
	53	nbits -= count_leading_zeros(buffer[0]);
	54	else
	55	nbits = 0;
	56
0d2a1b2d	57	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
e1045992 DH	58	val = mpi_alloc(nlimbs);
	59	if (!val)
	60	return NULL;
	61	val->nbits = nbits;
	62	val->sign = 0;
	63	val->nlimbs = nlimbs;
	64
	65	if (nbytes > 0) {
	66	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	67	i %= BYTES_PER_MPI_LIMB;
	68	for (j = nlimbs; j > 0; j--) {
	69	a = 0;
	70	for (; i < BYTES_PER_MPI_LIMB; i++) {
	71	a <<= 8;
	72	a \|= *buffer++;
	73	}
	74	i = 0;
	75	val->d[j - 1] = a;
	76	}
	77	}
	78	return val;
	79	}
	80	EXPORT_SYMBOL_GPL(mpi_read_raw_data);
	81
cdec9cb5 DK	82	MPI mpi_read_from_buffer(const void xbuffer, unsigned ret_nread)
	83	{
	84	const uint8_t *buffer = xbuffer;
	85	int i, j;
	86	unsigned nbits, nbytes, nlimbs, nread = 0;
	87	mpi_limb_t a;
3cccd154	88	MPI val = NULL;
cdec9cb5 DK	89
	90	if (*ret_nread < 2)
	91	goto leave;
	92	nbits = buffer[0] << 8 \| buffer[1];
	93
	94	if (nbits > MAX_EXTERN_MPI_BITS) {
	95	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	96	goto leave;
	97	}
	98	buffer += 2;
	99	nread = 2;
	100
0d2a1b2d AS	101	nbytes = DIV_ROUND_UP(nbits, 8);
0d2a1b2d AS	102	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
cdec9cb5 DK	103	val = mpi_alloc(nlimbs);
cdec9cb5 DK	104	if (!val)
3cccd154	105	return NULL;
cdec9cb5 DK	106	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	107	i %= BYTES_PER_MPI_LIMB;
	108	val->nbits = nbits;
	109	j = val->nlimbs = nlimbs;
	110	val->sign = 0;
	111	for (; j > 0; j--) {
	112	a = 0;
	113	for (; i < BYTES_PER_MPI_LIMB; i++) {
	114	if (++nread > *ret_nread) {
	115	printk
	116	("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
	117	nread, *ret_nread);
	118	goto leave;
	119	}
	120	a <<= 8;
	121	a \|= *buffer++;
	122	}
	123	i = 0;
	124	val->d[j - 1] = a;
	125	}
	126
	127	leave:
	128	*ret_nread = nread;
	129	return val;
	130	}
	131	EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
	132
3ee0cb5f MM	133	static int count_lzeros(MPI a)
	134	{
	135	mpi_limb_t alimb;
	136	int i, lzeros = 0;
	137
	138	for (i = a->nlimbs - 1; i >= 0; i--) {
	139	alimb = a->d[i];
	140	if (alimb == 0) {
	141	lzeros += sizeof(mpi_limb_t);
	142	} else {
	143	lzeros += count_leading_zeros(alimb) / 8;
	144	break;
	145	}
	146	}
	147	return lzeros;
	148	}
	149
d37e2969 TS	150	/**
	151	* mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
	152	*
	153	* @a: a multi precision integer
	154	* @buf: bufer to which the output will be written to. Needs to be at
	155	* leaset mpi_get_size(a) long.
	156	* @buf_len: size of the buf.
9cbe21d8 AZ	157	* @nbytes: receives the actual length of the data written on success and
	158	* the data to-be-written on -EOVERFLOW in case buf_len was too
	159	* small.
d37e2969 TS	160	* @sign: if not NULL, it will be set to the sign of a.
	161	*
	162	* Return: 0 on success or error code in case of error
cdec9cb5	163	*/
d37e2969 TS	164	int mpi_read_buffer(MPI a, uint8_t buf, unsigned buf_len, unsigned nbytes,
d37e2969 TS	165	int *sign)
cdec9cb5	166	{
d37e2969	167	uint8_t *p;
90f864e2 NS	168	#if BYTES_PER_MPI_LIMB == 4
	169	__be32 alimb;
	170	#elif BYTES_PER_MPI_LIMB == 8
	171	__be64 alimb;
	172	#else
	173	#error please implement for this limb size.
	174	#endif
d37e2969	175	unsigned int n = mpi_get_size(a);
3ee0cb5f	176	int i, lzeros;
d37e2969	177
9cbe21d8	178	if (!buf \|\| !nbytes)
d37e2969	179	return -EINVAL;
cdec9cb5 DK	180
	181	if (sign)
	182	*sign = a->sign;
d37e2969	183
3ee0cb5f	184	lzeros = count_lzeros(a);
d37e2969	185
9cbe21d8 AZ	186	if (buf_len < n - lzeros) {
	187	*nbytes = n - lzeros;
	188	return -EOVERFLOW;
	189	}
	190
d37e2969	191	p = buf;
0f74fbf7	192	*nbytes = n - lzeros;
cdec9cb5	193
f00fa241 NS	194	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
	195	lzeros %= BYTES_PER_MPI_LIMB;
	196	i >= 0; i--) {
cdec9cb5	197	#if BYTES_PER_MPI_LIMB == 4
90f864e2	198	alimb = cpu_to_be32(a->d[i]);
cdec9cb5	199	#elif BYTES_PER_MPI_LIMB == 8
90f864e2	200	alimb = cpu_to_be64(a->d[i]);
cdec9cb5 DK	201	#else
	202	#error please implement for this limb size.
	203	#endif
462696fd NS	204	memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);
	205	p += BYTES_PER_MPI_LIMB - lzeros;
	206	lzeros = 0;
cdec9cb5	207	}
d37e2969 TS	208	return 0;
	209	}
	210	EXPORT_SYMBOL_GPL(mpi_read_buffer);
	211
	212	/*
	213	* mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
	214	* Caller must free the return string.
	215	* This function does return a 0 byte buffer with nbytes set to zero if the
	216	* value of A is zero.
	217	*
	218	* @a: a multi precision integer.
	219	* @nbytes: receives the length of this buffer.
	220	* @sign: if not NULL, it will be set to the sign of the a.
	221	*
	222	* Return: Pointer to MPI buffer or NULL on error
	223	*/
	224	void mpi_get_buffer(MPI a, unsigned nbytes, int *sign)
	225	{
0f74fbf7	226	uint8_t *buf;
d37e2969 TS	227	unsigned int n;
	228	int ret;
	229
	230	if (!nbytes)
	231	return NULL;
	232
	233	n = mpi_get_size(a);
	234
	235	if (!n)
	236	n++;
	237
	238	buf = kmalloc(n, GFP_KERNEL);
	239
	240	if (!buf)
	241	return NULL;
	242
	243	ret = mpi_read_buffer(a, buf, n, nbytes, sign);
	244
	245	if (ret) {
	246	kfree(buf);
	247	return NULL;
	248	}
d37e2969	249	return buf;
cdec9cb5 DK	250	}
	251	EXPORT_SYMBOL_GPL(mpi_get_buffer);
	252
2d4d1eea TS	253	/**
	254	* mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
	255	*
	256	* This function works in the same way as the mpi_read_buffer, but it
	257	* takes an sgl instead of u8 * buf.
	258	*
	259	* @a: a multi precision integer
	260	* @sgl: scatterlist to write to. Needs to be at least
	261	* mpi_get_size(a) long.
	262	* @nbytes: in/out param - it has the be set to the maximum number of
	263	* bytes that can be written to sgl. This has to be at least
	264	* the size of the integer a. On return it receives the actual
9cbe21d8 AZ	265	* length of the data written on success or the data that would
9cbe21d8 AZ	266	* be written if buffer was too small.
2d4d1eea TS	267	* @sign: if not NULL, it will be set to the sign of a.
	268	*
	269	* Return: 0 on success or error code in case of error
	270	*/
	271	int mpi_write_to_sgl(MPI a, struct scatterlist sgl, unsigned nbytes,
	272	int *sign)
	273	{
	274	u8 p, p2;
d7552906 NS	275	#if BYTES_PER_MPI_LIMB == 4
	276	__be32 alimb;
	277	#elif BYTES_PER_MPI_LIMB == 8
	278	__be64 alimb;
	279	#else
	280	#error please implement for this limb size.
	281	#endif
2d4d1eea	282	unsigned int n = mpi_get_size(a);
3ee0cb5f	283	int i, x, y = 0, lzeros, buf_len;
2d4d1eea	284
9cbe21d8	285	if (!nbytes)
2d4d1eea TS	286	return -EINVAL;
	287
	288	if (sign)
	289	*sign = a->sign;
	290
3ee0cb5f	291	lzeros = count_lzeros(a);
2d4d1eea	292
9cbe21d8 AZ	293	if (*nbytes < n - lzeros) {
	294	*nbytes = n - lzeros;
	295	return -EOVERFLOW;
	296	}
	297
2d4d1eea TS	298	*nbytes = n - lzeros;
	299	buf_len = sgl->length;
	300	p2 = sg_virt(sgl);
	301
f2d1362f NS	302	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
	303	lzeros %= BYTES_PER_MPI_LIMB;
	304	i >= 0; i--) {
2d4d1eea	305	#if BYTES_PER_MPI_LIMB == 4
d7552906	306	alimb = cpu_to_be32(a->d[i]);
2d4d1eea	307	#elif BYTES_PER_MPI_LIMB == 8
d7552906	308	alimb = cpu_to_be64(a->d[i]);
2d4d1eea TS	309	#else
	310	#error please implement for this limb size.
	311	#endif
654842ef	312	if (lzeros) {
f2d1362f	313	y = lzeros;
654842ef	314	lzeros = 0;
2d4d1eea TS	315	}
2d4d1eea TS	316
d7552906	317	p = (u8 *)&alimb + y;
2d4d1eea TS	318
	319	for (x = 0; x < sizeof(alimb) - y; x++) {
	320	if (!buf_len) {
	321	sgl = sg_next(sgl);
	322	if (!sgl)
	323	return -EINVAL;
	324	buf_len = sgl->length;
	325	p2 = sg_virt(sgl);
	326	}
	327	p2++ = p++;
	328	buf_len--;
	329	}
	330	y = 0;
	331	}
	332	return 0;
	333	}
	334	EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
	335
	336	/*
	337	* mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
	338	* data from the sgl
	339	*
	340	* This function works in the same way as the mpi_read_raw_data, but it
	341	* takes an sgl instead of void * buffer. i.e. it allocates
	342	* a new MPI and reads the content of the sgl to the MPI.
	343	*
	344	* @sgl: scatterlist to read from
b6985389	345	* @nbytes: number of bytes to read
2d4d1eea TS	346	*
	347	* Return: Pointer to a new MPI or NULL on error
	348	*/
b6985389	349	MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
2d4d1eea TS	350	{
	351	struct scatterlist *sg;
	352	int x, i, j, z, lzeros, ents;
b6985389	353	unsigned int nbits, nlimbs;
2d4d1eea TS	354	mpi_limb_t a;
	355	MPI val = NULL;
	356
	357	lzeros = 0;
	358	ents = sg_nents(sgl);
	359
	360	for_each_sg(sgl, sg, ents, i) {
	361	const u8 *buff = sg_virt(sg);
	362	int len = sg->length;
	363
63349d02	364	while (len && !*buff) {
2d4d1eea	365	lzeros++;
63349d02 SM	366	len--;
	367	buff++;
	368	}
2d4d1eea TS	369
	370	if (len && *buff)
	371	break;
	372
	373	ents--;
ab1e912e	374	nbytes -= lzeros;
2d4d1eea TS	375	lzeros = 0;
	376	}
	377
	378	sgl = sg;
ab1e912e	379	nbytes -= lzeros;
2d4d1eea TS	380	nbits = nbytes * 8;
	381	if (nbits > MAX_EXTERN_MPI_BITS) {
	382	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	383	return NULL;
	384	}
	385
	386	if (nbytes > 0)
64c09b0b NS	387	nbits -= count_leading_zeros((u8 )(sg_virt(sgl) + lzeros)) -
64c09b0b NS	388	(BITS_PER_LONG - 8);
2d4d1eea TS	389
	390	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	391	val = mpi_alloc(nlimbs);
	392	if (!val)
	393	return NULL;
	394
	395	val->nbits = nbits;
	396	val->sign = 0;
	397	val->nlimbs = nlimbs;
	398
	399	if (nbytes == 0)
	400	return val;
	401
	402	j = nlimbs - 1;
	403	a = 0;
85d541a3 NS	404	z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
85d541a3 NS	405	z %= BYTES_PER_MPI_LIMB;
2d4d1eea TS	406
	407	for_each_sg(sgl, sg, ents, i) {
	408	const u8 *buffer = sg_virt(sg) + lzeros;
	409	int len = sg->length - lzeros;
2d4d1eea	410
85d541a3	411	for (x = 0; x < len; x++) {
2d4d1eea TS	412	a <<= 8;
	413	a \|= *buffer++;
	414	if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
	415	val->d[j--] = a;
	416	a = 0;
	417	}
	418	}
	419	z += x;
2d4d1eea TS	420	lzeros = 0;
	421	}
	422	return val;
	423	}
	424	EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);