[deliverable/linux.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 "mpi-internal.h"

#define DIM(v) (sizeof(v)/sizeof((v)[0]))
#define MAX_EXTERN_MPI_BITS 16384

static uint8_t asn[15] =	/* Object ID is 1.3.14.3.2.26 */
{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
	0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
};

MPI do_encode_md(const void *sha_buffer, unsigned nbits)
{
	int nframe = (nbits + 7) / 8;
	uint8_t *frame, *fr_pt;
	int i = 0, n;
	size_t asnlen = DIM(asn);
	MPI a = MPI_NULL;

	if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
		pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
		       (int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);

	/* We encode the MD in this way:
	 *
	 *       0  A PAD(n bytes)   0  ASN(asnlen bytes)  MD(len bytes)
	 *
	 * PAD consists of FF bytes.
	 */
	frame = kmalloc(nframe, GFP_KERNEL);
	if (!frame)
		return MPI_NULL;
	n = 0;
	frame[n++] = 0;
	frame[n++] = 1;		/* block type */
	i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;

	if (i <= 1) {
		pr_info("MPI: message digest encoding failed\n");
		kfree(frame);
		return a;
	}

	memset(frame + n, 0xff, i);
	n += i;
	frame[n++] = 0;
	memcpy(frame + n, &asn, asnlen);
	n += asnlen;
	memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
	n += SHA1_DIGEST_LENGTH;

	i = nframe;
	fr_pt = frame;

	if (n != nframe) {
		printk
		    ("MPI: message digest encoding failed, frame length is wrong\n");
		kfree(frame);
		return a;
	}

	a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
	if (a)
		mpi_set_buffer(a, frame, nframe, 0);
	kfree(frame);

	return a;
}

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 = MPI_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 = (nbits + 7) / 8;
	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
	val = mpi_alloc(nlimbs);
	if (!val)
		return MPI_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);

/****************
 * Make an mpi from a character string.
 */
int mpi_fromstr(MPI val, const char *str)
{
	int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
	unsigned nbits, nbytes, nlimbs;
	mpi_limb_t a;

	if (*str == '-') {
		sign = 1;
		str++;
	}
	if (*str == '0' && str[1] == 'x')
		hexmode = 1;
	else
		return -EINVAL;	/* other bases are not yet supported */
	str += 2;

	nbits = strlen(str) * 4;
	if (nbits % 8)
		prepend_zero = 1;
	nbytes = (nbits + 7) / 8;
	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
	if (val->alloced < nlimbs)
		if (!mpi_resize(val, nlimbs))
			return -ENOMEM;
	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	i %= BYTES_PER_MPI_LIMB;
	j = val->nlimbs = nlimbs;
	val->sign = sign;
	for (; j > 0; j--) {
		a = 0;
		for (; i < BYTES_PER_MPI_LIMB; i++) {
			if (prepend_zero) {
				c1 = '0';
				prepend_zero = 0;
			} else
				c1 = *str++;
			assert(c1);
			c2 = *str++;
			assert(c2);
			if (c1 >= '0' && c1 <= '9')
				c = c1 - '0';
			else if (c1 >= 'a' && c1 <= 'f')
				c = c1 - 'a' + 10;
			else if (c1 >= 'A' && c1 <= 'F')
				c = c1 - 'A' + 10;
			else {
				mpi_clear(val);
				return 1;
			}
			c <<= 4;
			if (c2 >= '0' && c2 <= '9')
				c |= c2 - '0';
			else if (c2 >= 'a' && c2 <= 'f')
				c |= c2 - 'a' + 10;
			else if (c2 >= 'A' && c2 <= 'F')
				c |= c2 - 'A' + 10;
			else {
				mpi_clear(val);
				return 1;
			}
			a <<= 8;
			a |= c;
		}
		i = 0;

		val->d[j - 1] = a;
	}

	return 0;
}
EXPORT_SYMBOL_GPL(mpi_fromstr);

/****************
 * Special function to get the low 8 bytes from an mpi.
 * This can be used as a keyid; KEYID is an 2 element array.
 * Return the low 4 bytes.
 */
u32 mpi_get_keyid(const MPI a, u32 *keyid)
{
#if BYTES_PER_MPI_LIMB == 4
	if (keyid) {
		keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
		keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
	}
	return a->nlimbs >= 1 ? a->d[0] : 0;
#elif BYTES_PER_MPI_LIMB == 8
	if (keyid) {
		keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
		keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
	}
	return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
#else
#error Make this function work with other LIMB sizes
#endif
}

/****************
 * Return an allocated buffer with the MPI (msb first).
 * NBYTES receives the length of this buffer. 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. If sign is not NULL, it will
 * be set to the sign of the A.
 */
void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
{
	uint8_t *p, *buffer;
	mpi_limb_t alimb;
	int i;
	unsigned int n;

	if (sign)
		*sign = a->sign;
	*nbytes = n = a->nlimbs * BYTES_PER_MPI_LIMB;
	if (!n)
		n++;		/* avoid zero length allocation */
	p = buffer = kmalloc(n, GFP_KERNEL);
	if (!p)
		return NULL;

	for (i = a->nlimbs - 1; i >= 0; i--) {
		alimb = a->d[i];
#if BYTES_PER_MPI_LIMB == 4
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#elif BYTES_PER_MPI_LIMB == 8
		*p++ = alimb >> 56;
		*p++ = alimb >> 48;
		*p++ = alimb >> 40;
		*p++ = alimb >> 32;
		*p++ = alimb >> 24;
		*p++ = alimb >> 16;
		*p++ = alimb >> 8;
		*p++ = alimb;
#else
#error please implement for this limb size.
#endif
	}

	/* this is sub-optimal but we need to do the shift operation
	 * because the caller has to free the returned buffer */
	for (p = buffer; !*p && *nbytes; p++, --*nbytes)
		;
	if (p != buffer)
		memmove(buffer, p, *nbytes);

	return buffer;
}
EXPORT_SYMBOL_GPL(mpi_get_buffer);

/****************
 * Use BUFFER to update MPI.
 */
int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
{
	const uint8_t *buffer = xbuffer, *p;
	mpi_limb_t alimb;
	int nlimbs;
	int i;

	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
		return -ENOMEM;
	a->sign = sign;

	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = (mpi_limb_t) *p--;
		alimb |= (mpi_limb_t) *p-- << 8;
		alimb |= (mpi_limb_t) *p-- << 16;
		alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
		alimb = (mpi_limb_t) *p--;
		alimb |= (mpi_limb_t) *p-- << 8;
		alimb |= (mpi_limb_t) *p-- << 16;
		alimb |= (mpi_limb_t) *p-- << 24;
		alimb |= (mpi_limb_t) *p-- << 32;
		alimb |= (mpi_limb_t) *p-- << 40;
		alimb |= (mpi_limb_t) *p-- << 48;
		alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
		a->d[i++] = alimb;
	}
	if (p >= buffer) {
#if BYTES_PER_MPI_LIMB == 4
		alimb = *p--;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 8;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 16;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 24;
#elif BYTES_PER_MPI_LIMB == 8
		alimb = (mpi_limb_t) *p--;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 8;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 16;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 24;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 32;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 40;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 48;
		if (p >= buffer)
			alimb |= (mpi_limb_t) *p-- << 56;
#else
#error please implement for this limb size.
#endif
		a->d[i++] = alimb;
	}
	a->nlimbs = i;

	if (i != nlimbs) {
		pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
		       nlimbs);
		BUG();
	}
	return 0;
}
EXPORT_SYMBOL_GPL(mpi_set_buffer);
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
	21	#include "mpi-internal.h"
	22
	23	#define DIM(v) (sizeof(v)/sizeof((v)[0]))
	24	#define MAX_EXTERN_MPI_BITS 16384
	25
	26	static uint8_t asn[15] = /* Object ID is 1.3.14.3.2.26 */
	27	{ 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2b, 0x0e, 0x03,
	28	0x02, 0x1a, 0x05, 0x00, 0x04, 0x14
	29	};
	30
	31	MPI do_encode_md(const void *sha_buffer, unsigned nbits)
	32	{
	33	int nframe = (nbits + 7) / 8;
	34	uint8_t frame, fr_pt;
	35	int i = 0, n;
	36	size_t asnlen = DIM(asn);
	37	MPI a = MPI_NULL;
	38
	39	if (SHA1_DIGEST_LENGTH + asnlen + 4 > nframe)
	40	pr_info("MPI: can't encode a %d bit MD into a %d bits frame\n",
	41	(int)(SHA1_DIGEST_LENGTH * 8), (int)nbits);
	42
	43	/* We encode the MD in this way:
	44	*
	45	* 0 A PAD(n bytes) 0 ASN(asnlen bytes) MD(len bytes)
	46	*
	47	* PAD consists of FF bytes.
	48	*/
	49	frame = kmalloc(nframe, GFP_KERNEL);
	50	if (!frame)
	51	return MPI_NULL;
	52	n = 0;
	53	frame[n++] = 0;
	54	frame[n++] = 1; /* block type */
	55	i = nframe - SHA1_DIGEST_LENGTH - asnlen - 3;
	56
	57	if (i <= 1) {
	58	pr_info("MPI: message digest encoding failed\n");
	59	kfree(frame);
	60	return a;
	61	}
	62
	63	memset(frame + n, 0xff, i);
	64	n += i;
65	frame[n++] = 0;
66	memcpy(frame + n, &asn, asnlen);
67	n += asnlen;
68	memcpy(frame + n, sha_buffer, SHA1_DIGEST_LENGTH);
69	n += SHA1_DIGEST_LENGTH;
70
71	i = nframe;
72	fr_pt = frame;
73
74	if (n != nframe) {
75	printk
76	("MPI: message digest encoding failed, frame length is wrong\n");
77	kfree(frame);
78	return a;
79	}
80
81	a = mpi_alloc((nframe + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB);
c70c471c DK	82	if (a)
c70c471c DK	83	mpi_set_buffer(a, frame, nframe, 0);
cdec9cb5 DK	84	kfree(frame);
	85
	86	return a;
	87	}
	88
	89	MPI mpi_read_from_buffer(const void xbuffer, unsigned ret_nread)
	90	{
	91	const uint8_t *buffer = xbuffer;
	92	int i, j;
	93	unsigned nbits, nbytes, nlimbs, nread = 0;
	94	mpi_limb_t a;
	95	MPI val = MPI_NULL;
	96
	97	if (*ret_nread < 2)
	98	goto leave;
	99	nbits = buffer[0] << 8 \| buffer[1];
	100
	101	if (nbits > MAX_EXTERN_MPI_BITS) {
	102	pr_info("MPI: mpi too large (%u bits)\n", nbits);
	103	goto leave;
	104	}
	105	buffer += 2;
	106	nread = 2;
	107
	108	nbytes = (nbits + 7) / 8;
	109	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
	110	val = mpi_alloc(nlimbs);
	111	if (!val)
	112	return MPI_NULL;
	113	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
	114	i %= BYTES_PER_MPI_LIMB;
	115	val->nbits = nbits;
	116	j = val->nlimbs = nlimbs;
	117	val->sign = 0;
	118	for (; j > 0; j--) {
	119	a = 0;
	120	for (; i < BYTES_PER_MPI_LIMB; i++) {
	121	if (++nread > *ret_nread) {
	122	printk
	123	("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
	124	nread, *ret_nread);
	125	goto leave;
	126	}
	127	a <<= 8;
	128	a \|= *buffer++;
	129	}
	130	i = 0;
	131	val->d[j - 1] = a;
	132	}
	133
	134	leave:
	135	*ret_nread = nread;
	136	return val;
	137	}
	138	EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
	139
	140	/****************
	141	* Make an mpi from a character string.
	142	*/
	143	int mpi_fromstr(MPI val, const char *str)
	144	{
	145	int hexmode = 0, sign = 0, prepend_zero = 0, i, j, c, c1, c2;
	146	unsigned nbits, nbytes, nlimbs;
	147	mpi_limb_t a;
148
149	if (*str == '-') {
150	sign = 1;
151	str++;
152	}
153	if (*str == '0' && str[1] == 'x')
154	hexmode = 1;
155	else
156	return -EINVAL; /* other bases are not yet supported */
157	str += 2;
158
159	nbits = strlen(str) * 4;
160	if (nbits % 8)
161	prepend_zero = 1;
162	nbytes = (nbits + 7) / 8;
163	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
164	if (val->alloced < nlimbs)
165	if (!mpi_resize(val, nlimbs))
166	return -ENOMEM;
167	i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
168	i %= BYTES_PER_MPI_LIMB;
169	j = val->nlimbs = nlimbs;
170	val->sign = sign;
171	for (; j > 0; j--) {
172	a = 0;
173	for (; i < BYTES_PER_MPI_LIMB; i++) {
174	if (prepend_zero) {
175	c1 = '0';
176	prepend_zero = 0;
177	} else
178	c1 = *str++;
179	assert(c1);
180	c2 = *str++;
181	assert(c2);
182	if (c1 >= '0' && c1 <= '9')
183	c = c1 - '0';
184	else if (c1 >= 'a' && c1 <= 'f')
185	c = c1 - 'a' + 10;
186	else if (c1 >= 'A' && c1 <= 'F')
187	c = c1 - 'A' + 10;
188	else {
189	mpi_clear(val);
190	return 1;
191	}
192	c <<= 4;
193	if (c2 >= '0' && c2 <= '9')
194	c \|= c2 - '0';
195	else if (c2 >= 'a' && c2 <= 'f')
196	c \|= c2 - 'a' + 10;
197	else if (c2 >= 'A' && c2 <= 'F')
198	c \|= c2 - 'A' + 10;
199	else {
200	mpi_clear(val);
201	return 1;
202	}
203	a <<= 8;
204	a \|= c;
205	}
206	i = 0;
207
208	val->d[j - 1] = a;
209	}
210
211	return 0;
212	}
213	EXPORT_SYMBOL_GPL(mpi_fromstr);
214
215	/****************
216	* Special function to get the low 8 bytes from an mpi.
217	* This can be used as a keyid; KEYID is an 2 element array.
218	* Return the low 4 bytes.
219	*/
220	u32 mpi_get_keyid(const MPI a, u32 *keyid)
221	{
222	#if BYTES_PER_MPI_LIMB == 4
223	if (keyid) {
224	keyid[0] = a->nlimbs >= 2 ? a->d[1] : 0;
225	keyid[1] = a->nlimbs >= 1 ? a->d[0] : 0;
226	}
227	return a->nlimbs >= 1 ? a->d[0] : 0;
228	#elif BYTES_PER_MPI_LIMB == 8
229	if (keyid) {
230	keyid[0] = a->nlimbs ? (u32) (a->d[0] >> 32) : 0;
231	keyid[1] = a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
232	}
233	return a->nlimbs ? (u32) (a->d[0] & 0xffffffff) : 0;
234	#else
235	#error Make this function work with other LIMB sizes
236	#endif
237	}
238
239	/****************
240	* Return an allocated buffer with the MPI (msb first).
241	* NBYTES receives the length of this buffer. Caller must free the
242	* return string (This function does return a 0 byte buffer with NBYTES
243	* set to zero if the value of A is zero. If sign is not NULL, it will
244	* be set to the sign of the A.
245	*/
246	void mpi_get_buffer(MPI a, unsigned nbytes, int *sign)
247	{
248	uint8_t p, buffer;
249	mpi_limb_t alimb;
250	int i;
251	unsigned int n;
252
253	if (sign)
254	*sign = a->sign;
255	nbytes = n = a->nlimbs BYTES_PER_MPI_LIMB;
256	if (!n)
257	n++; /* avoid zero length allocation */
258	p = buffer = kmalloc(n, GFP_KERNEL);
4bf1924c DH	259	if (!p)
4bf1924c DH	260	return NULL;
cdec9cb5 DK	261
	262	for (i = a->nlimbs - 1; i >= 0; i--) {
	263	alimb = a->d[i];
	264	#if BYTES_PER_MPI_LIMB == 4
	265	*p++ = alimb >> 24;
	266	*p++ = alimb >> 16;
	267	*p++ = alimb >> 8;
	268	*p++ = alimb;
	269	#elif BYTES_PER_MPI_LIMB == 8
	270	*p++ = alimb >> 56;
	271	*p++ = alimb >> 48;
	272	*p++ = alimb >> 40;
	273	*p++ = alimb >> 32;
	274	*p++ = alimb >> 24;
	275	*p++ = alimb >> 16;
	276	*p++ = alimb >> 8;
	277	*p++ = alimb;
	278	#else
	279	#error please implement for this limb size.
	280	#endif
	281	}
	282
	283	/* this is sub-optimal but we need to do the shift operation
	284	* because the caller has to free the returned buffer */
	285	for (p = buffer; !p && nbytes; p++, --*nbytes)
	286	;
	287	if (p != buffer)
	288	memmove(buffer, p, *nbytes);
	289
	290	return buffer;
	291	}
	292	EXPORT_SYMBOL_GPL(mpi_get_buffer);
	293
	294	/****************
	295	* Use BUFFER to update MPI.
	296	*/
	297	int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
	298	{
	299	const uint8_t buffer = xbuffer, p;
	300	mpi_limb_t alimb;
	301	int nlimbs;
	302	int i;
	303
	304	nlimbs = (nbytes + BYTES_PER_MPI_LIMB - 1) / BYTES_PER_MPI_LIMB;
	305	if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
	306	return -ENOMEM;
	307	a->sign = sign;
	308
	309	for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
	310	#if BYTES_PER_MPI_LIMB == 4
	311	alimb = (mpi_limb_t) *p--;
	312	alimb \|= (mpi_limb_t) *p-- << 8;
	313	alimb \|= (mpi_limb_t) *p-- << 16;
	314	alimb \|= (mpi_limb_t) *p-- << 24;
	315	#elif BYTES_PER_MPI_LIMB == 8
	316	alimb = (mpi_limb_t) *p--;
	317	alimb \|= (mpi_limb_t) *p-- << 8;
	318	alimb \|= (mpi_limb_t) *p-- << 16;
	319	alimb \|= (mpi_limb_t) *p-- << 24;
	320	alimb \|= (mpi_limb_t) *p-- << 32;
	321	alimb \|= (mpi_limb_t) *p-- << 40;
	322	alimb \|= (mpi_limb_t) *p-- << 48;
	323	alimb \|= (mpi_limb_t) *p-- << 56;
	324	#else
325	#error please implement for this limb size.
326	#endif
327	a->d[i++] = alimb;
328	}
329	if (p >= buffer) {
330	#if BYTES_PER_MPI_LIMB == 4
331	alimb = *p--;
332	if (p >= buffer)
333	alimb \|= (mpi_limb_t) *p-- << 8;
334	if (p >= buffer)
335	alimb \|= (mpi_limb_t) *p-- << 16;
336	if (p >= buffer)
337	alimb \|= (mpi_limb_t) *p-- << 24;
338	#elif BYTES_PER_MPI_LIMB == 8
339	alimb = (mpi_limb_t) *p--;
340	if (p >= buffer)
341	alimb \|= (mpi_limb_t) *p-- << 8;
342	if (p >= buffer)
343	alimb \|= (mpi_limb_t) *p-- << 16;
344	if (p >= buffer)
345	alimb \|= (mpi_limb_t) *p-- << 24;
346	if (p >= buffer)
347	alimb \|= (mpi_limb_t) *p-- << 32;
348	if (p >= buffer)
349	alimb \|= (mpi_limb_t) *p-- << 40;
350	if (p >= buffer)
351	alimb \|= (mpi_limb_t) *p-- << 48;
352	if (p >= buffer)
353	alimb \|= (mpi_limb_t) *p-- << 56;
354	#else
355	#error please implement for this limb size.
356	#endif
357	a->d[i++] = alimb;
358	}
359	a->nlimbs = i;
360
361	if (i != nlimbs) {
362	pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
363	nlimbs);
364	BUG();
365	}
366	return 0;
367	}
368	EXPORT_SYMBOL_GPL(mpi_set_buffer);