[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]) - (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) {
		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)
eef0df6a	53	nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8);
e1045992	54
0d2a1b2d	55	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
e1045992 DH	56	val = mpi_alloc(nlimbs);
	57	if (!val)
	58	return NULL;
	59	val->nbits = nbits;
	60	val->sign = 0;
	61	val->nlimbs = nlimbs;
	62
	63	if (nbytes > 0) {
	64	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	65	i %= BYTES_PER_MPI_LIMB;
	66	for (j = nlimbs; j > 0; j--) {
	67	a = 0;
	68	for (; i < BYTES_PER_MPI_LIMB; i++) {
	69	a <<= 8;
	70	a \|= *buffer++;
	71	}
	72	i = 0;
	73	val->d[j - 1] = a;
	74	}
	75	}
	76	return val;
	77	}
	78	EXPORT_SYMBOL_GPL(mpi_read_raw_data);
	79
cdec9cb5 DK	80	MPI mpi_read_from_buffer(const void xbuffer, unsigned ret_nread)
	81	{
	82	const uint8_t *buffer = xbuffer;
	83	int i, j;
	84	unsigned nbits, nbytes, nlimbs, nread = 0;
	85	mpi_limb_t a;
3cccd154	86	MPI val = NULL;
cdec9cb5 DK	87
	88	if (*ret_nread < 2)
	89	goto leave;
	90	nbits = buffer[0] << 8 \| buffer[1];
	91
	92	if (nbits > MAX_EXTERN_MPI_BITS) {
	93	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	94	goto leave;
	95	}
	96	buffer += 2;
	97	nread = 2;
	98
0d2a1b2d AS	99	nbytes = DIV_ROUND_UP(nbits, 8);
0d2a1b2d AS	100	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
cdec9cb5 DK	101	val = mpi_alloc(nlimbs);
cdec9cb5 DK	102	if (!val)
3cccd154	103	return NULL;
cdec9cb5 DK	104	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	105	i %= BYTES_PER_MPI_LIMB;
	106	val->nbits = nbits;
	107	j = val->nlimbs = nlimbs;
	108	val->sign = 0;
	109	for (; j > 0; j--) {
	110	a = 0;
	111	for (; i < BYTES_PER_MPI_LIMB; i++) {
	112	if (++nread > *ret_nread) {
	113	printk
	114	("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
	115	nread, *ret_nread);
	116	goto leave;
	117	}
	118	a <<= 8;
	119	a \|= *buffer++;
	120	}
	121	i = 0;
	122	val->d[j - 1] = a;
	123	}
	124
	125	leave:
	126	*ret_nread = nread;
	127	return val;
	128	}
	129	EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
	130
3ee0cb5f MM	131	static int count_lzeros(MPI a)
	132	{
	133	mpi_limb_t alimb;
	134	int i, lzeros = 0;
	135
	136	for (i = a->nlimbs - 1; i >= 0; i--) {
	137	alimb = a->d[i];
	138	if (alimb == 0) {
	139	lzeros += sizeof(mpi_limb_t);
	140	} else {
	141	lzeros += count_leading_zeros(alimb) / 8;
	142	break;
	143	}
	144	}
	145	return lzeros;
	146	}
	147
d37e2969 TS	148	/**
	149	* mpi_read_buffer() - read MPI to a bufer provided by user (msb first)
	150	*
	151	* @a: a multi precision integer
	152	* @buf: bufer to which the output will be written to. Needs to be at
	153	* leaset mpi_get_size(a) long.
	154	* @buf_len: size of the buf.
9cbe21d8 AZ	155	* @nbytes: receives the actual length of the data written on success and
	156	* the data to-be-written on -EOVERFLOW in case buf_len was too
	157	* small.
d37e2969 TS	158	* @sign: if not NULL, it will be set to the sign of a.
	159	*
	160	* Return: 0 on success or error code in case of error
cdec9cb5	161	*/
d37e2969 TS	162	int mpi_read_buffer(MPI a, uint8_t buf, unsigned buf_len, unsigned nbytes,
d37e2969 TS	163	int *sign)
cdec9cb5	164	{
d37e2969	165	uint8_t *p;
90f864e2 NS	166	#if BYTES_PER_MPI_LIMB == 4
	167	__be32 alimb;
	168	#elif BYTES_PER_MPI_LIMB == 8
	169	__be64 alimb;
	170	#else
	171	#error please implement for this limb size.
	172	#endif
d37e2969	173	unsigned int n = mpi_get_size(a);
3ee0cb5f	174	int i, lzeros;
d37e2969	175
9cbe21d8	176	if (!buf \|\| !nbytes)
d37e2969	177	return -EINVAL;
cdec9cb5 DK	178
	179	if (sign)
	180	*sign = a->sign;
d37e2969	181
3ee0cb5f	182	lzeros = count_lzeros(a);
d37e2969	183
9cbe21d8 AZ	184	if (buf_len < n - lzeros) {
	185	*nbytes = n - lzeros;
	186	return -EOVERFLOW;
	187	}
	188
d37e2969	189	p = buf;
0f74fbf7	190	*nbytes = n - lzeros;
cdec9cb5	191
f00fa241 NS	192	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
	193	lzeros %= BYTES_PER_MPI_LIMB;
	194	i >= 0; i--) {
cdec9cb5	195	#if BYTES_PER_MPI_LIMB == 4
90f864e2	196	alimb = cpu_to_be32(a->d[i]);
cdec9cb5	197	#elif BYTES_PER_MPI_LIMB == 8
90f864e2	198	alimb = cpu_to_be64(a->d[i]);
cdec9cb5 DK	199	#else
	200	#error please implement for this limb size.
	201	#endif
462696fd NS	202	memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);
	203	p += BYTES_PER_MPI_LIMB - lzeros;
	204	lzeros = 0;
cdec9cb5	205	}
d37e2969 TS	206	return 0;
	207	}
	208	EXPORT_SYMBOL_GPL(mpi_read_buffer);
	209
	210	/*
	211	* mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
	212	* Caller must free the return string.
	213	* This function does return a 0 byte buffer with nbytes set to zero if the
	214	* value of A is zero.
	215	*
	216	* @a: a multi precision integer.
	217	* @nbytes: receives the length of this buffer.
	218	* @sign: if not NULL, it will be set to the sign of the a.
	219	*
	220	* Return: Pointer to MPI buffer or NULL on error
	221	*/
	222	void mpi_get_buffer(MPI a, unsigned nbytes, int *sign)
	223	{
0f74fbf7	224	uint8_t *buf;
d37e2969 TS	225	unsigned int n;
	226	int ret;
	227
	228	if (!nbytes)
	229	return NULL;
	230
	231	n = mpi_get_size(a);
	232
	233	if (!n)
	234	n++;
	235
	236	buf = kmalloc(n, GFP_KERNEL);
	237
	238	if (!buf)
	239	return NULL;
	240
	241	ret = mpi_read_buffer(a, buf, n, nbytes, sign);
	242
	243	if (ret) {
	244	kfree(buf);
	245	return NULL;
	246	}
d37e2969	247	return buf;
cdec9cb5 DK	248	}
	249	EXPORT_SYMBOL_GPL(mpi_get_buffer);
	250
2d4d1eea TS	251	/**
	252	* mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
	253	*
	254	* This function works in the same way as the mpi_read_buffer, but it
	255	* takes an sgl instead of u8 * buf.
	256	*
	257	* @a: a multi precision integer
	258	* @sgl: scatterlist to write to. Needs to be at least
	259	* mpi_get_size(a) long.
	260	* @nbytes: in/out param - it has the be set to the maximum number of
	261	* bytes that can be written to sgl. This has to be at least
	262	* the size of the integer a. On return it receives the actual
9cbe21d8 AZ	263	* length of the data written on success or the data that would
9cbe21d8 AZ	264	* be written if buffer was too small.
2d4d1eea TS	265	* @sign: if not NULL, it will be set to the sign of a.
	266	*
	267	* Return: 0 on success or error code in case of error
	268	*/
	269	int mpi_write_to_sgl(MPI a, struct scatterlist sgl, unsigned nbytes,
	270	int *sign)
	271	{
	272	u8 p, p2;
d7552906 NS	273	#if BYTES_PER_MPI_LIMB == 4
	274	__be32 alimb;
	275	#elif BYTES_PER_MPI_LIMB == 8
	276	__be64 alimb;
	277	#else
	278	#error please implement for this limb size.
	279	#endif
2d4d1eea	280	unsigned int n = mpi_get_size(a);
3ee0cb5f	281	int i, x, y = 0, lzeros, buf_len;
2d4d1eea	282
9cbe21d8	283	if (!nbytes)
2d4d1eea TS	284	return -EINVAL;
	285
	286	if (sign)
	287	*sign = a->sign;
	288
3ee0cb5f	289	lzeros = count_lzeros(a);
2d4d1eea	290
9cbe21d8 AZ	291	if (*nbytes < n - lzeros) {
	292	*nbytes = n - lzeros;
	293	return -EOVERFLOW;
	294	}
	295
2d4d1eea TS	296	*nbytes = n - lzeros;
	297	buf_len = sgl->length;
	298	p2 = sg_virt(sgl);
	299
f2d1362f NS	300	for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
	301	lzeros %= BYTES_PER_MPI_LIMB;
	302	i >= 0; i--) {
2d4d1eea	303	#if BYTES_PER_MPI_LIMB == 4
d7552906	304	alimb = cpu_to_be32(a->d[i]);
2d4d1eea	305	#elif BYTES_PER_MPI_LIMB == 8
d7552906	306	alimb = cpu_to_be64(a->d[i]);
2d4d1eea TS	307	#else
	308	#error please implement for this limb size.
	309	#endif
654842ef	310	if (lzeros) {
f2d1362f	311	y = lzeros;
654842ef	312	lzeros = 0;
2d4d1eea TS	313	}
2d4d1eea TS	314
d7552906	315	p = (u8 *)&alimb + y;
2d4d1eea TS	316
	317	for (x = 0; x < sizeof(alimb) - y; x++) {
	318	if (!buf_len) {
	319	sgl = sg_next(sgl);
	320	if (!sgl)
	321	return -EINVAL;
	322	buf_len = sgl->length;
	323	p2 = sg_virt(sgl);
	324	}
	325	p2++ = p++;
	326	buf_len--;
	327	}
	328	y = 0;
	329	}
	330	return 0;
	331	}
	332	EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
	333
	334	/*
	335	* mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
	336	* data from the sgl
	337	*
	338	* This function works in the same way as the mpi_read_raw_data, but it
	339	* takes an sgl instead of void * buffer. i.e. it allocates
	340	* a new MPI and reads the content of the sgl to the MPI.
	341	*
	342	* @sgl: scatterlist to read from
b6985389	343	* @nbytes: number of bytes to read
2d4d1eea TS	344	*
	345	* Return: Pointer to a new MPI or NULL on error
	346	*/
b6985389	347	MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
2d4d1eea TS	348	{
	349	struct scatterlist *sg;
	350	int x, i, j, z, lzeros, ents;
b6985389	351	unsigned int nbits, nlimbs;
2d4d1eea TS	352	mpi_limb_t a;
	353	MPI val = NULL;
	354
	355	lzeros = 0;
	356	ents = sg_nents(sgl);
	357
	358	for_each_sg(sgl, sg, ents, i) {
	359	const u8 *buff = sg_virt(sg);
	360	int len = sg->length;
	361
63349d02	362	while (len && !*buff) {
2d4d1eea	363	lzeros++;
63349d02 SM	364	len--;
	365	buff++;
	366	}
2d4d1eea TS	367
	368	if (len && *buff)
	369	break;
	370
	371	ents--;
ab1e912e	372	nbytes -= lzeros;
2d4d1eea TS	373	lzeros = 0;
	374	}
	375
	376	sgl = sg;
ab1e912e	377	nbytes -= lzeros;
2d4d1eea TS	378	nbits = nbytes * 8;
	379	if (nbits > MAX_EXTERN_MPI_BITS) {
	380	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	381	return NULL;
	382	}
	383
	384	if (nbytes > 0)
64c09b0b NS	385	nbits -= count_leading_zeros((u8 )(sg_virt(sgl) + lzeros)) -
64c09b0b NS	386	(BITS_PER_LONG - 8);
2d4d1eea TS	387
	388	nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
	389	val = mpi_alloc(nlimbs);
	390	if (!val)
	391	return NULL;
	392
	393	val->nbits = nbits;
	394	val->sign = 0;
	395	val->nlimbs = nlimbs;
	396
	397	if (nbytes == 0)
	398	return val;
	399
	400	j = nlimbs - 1;
	401	a = 0;
85d541a3 NS	402	z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
85d541a3 NS	403	z %= BYTES_PER_MPI_LIMB;
2d4d1eea TS	404
	405	for_each_sg(sgl, sg, ents, i) {
	406	const u8 *buffer = sg_virt(sg) + lzeros;
	407	int len = sg->length - lzeros;
2d4d1eea	408
85d541a3	409	for (x = 0; x < len; x++) {
2d4d1eea TS	410	a <<= 8;
	411	a \|= *buffer++;
	412	if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
	413	val->d[j--] = a;
	414	a = 0;
	415	}
	416	}
	417	z += x;
2d4d1eea TS	418	lzeros = 0;
	419	}
	420	return val;
	421	}
	422	EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);