lib/mpi/mpicoder.c - kernel/msm-4.9 - Gitiles

 /* 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);
 	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);
	/* 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);
	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);