753 lines
16 KiB
C
753 lines
16 KiB
C
/* mpicoder.c - Coder for the external representation of MPIs
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* Copyright (C) 1998, 1999 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <linux/bitops.h>
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#include <linux/count_zeros.h>
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#include <linux/byteorder/generic.h>
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#include <linux/scatterlist.h>
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#include <linux/string.h>
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#include "mpi-internal.h"
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#define MAX_EXTERN_SCAN_BYTES (16*1024*1024)
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#define MAX_EXTERN_MPI_BITS 16384
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/**
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* mpi_read_raw_data - Read a raw byte stream as a positive integer
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* @xbuffer: The data to read
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* @nbytes: The amount of data to read
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*/
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MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
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{
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const uint8_t *buffer = xbuffer;
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int i, j;
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unsigned nbits, nlimbs;
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mpi_limb_t a;
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MPI val = NULL;
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while (nbytes > 0 && buffer[0] == 0) {
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buffer++;
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nbytes--;
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}
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nbits = nbytes * 8;
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if (nbits > MAX_EXTERN_MPI_BITS) {
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pr_info("MPI: mpi too large (%u bits)\n", nbits);
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return NULL;
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}
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if (nbytes > 0)
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nbits -= count_leading_zeros(buffer[0]) - (BITS_PER_LONG - 8);
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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val = mpi_alloc(nlimbs);
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if (!val)
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return NULL;
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val->nbits = nbits;
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val->sign = 0;
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val->nlimbs = nlimbs;
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if (nbytes > 0) {
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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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for (j = nlimbs; j > 0; j--) {
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a = 0;
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for (; i < BYTES_PER_MPI_LIMB; i++) {
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a <<= 8;
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a |= *buffer++;
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}
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i = 0;
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val->d[j - 1] = a;
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}
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}
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return val;
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}
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EXPORT_SYMBOL_GPL(mpi_read_raw_data);
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MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
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{
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const uint8_t *buffer = xbuffer;
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unsigned int nbits, nbytes;
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MPI val;
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if (*ret_nread < 2)
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return ERR_PTR(-EINVAL);
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nbits = buffer[0] << 8 | buffer[1];
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if (nbits > MAX_EXTERN_MPI_BITS) {
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pr_info("MPI: mpi too large (%u bits)\n", nbits);
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return ERR_PTR(-EINVAL);
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}
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nbytes = DIV_ROUND_UP(nbits, 8);
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if (nbytes + 2 > *ret_nread) {
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pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n",
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nbytes, *ret_nread);
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return ERR_PTR(-EINVAL);
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}
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val = mpi_read_raw_data(buffer + 2, nbytes);
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if (!val)
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return ERR_PTR(-ENOMEM);
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*ret_nread = nbytes + 2;
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return val;
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}
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EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
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/****************
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* Fill the mpi VAL from the hex string in STR.
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*/
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int mpi_fromstr(MPI val, const char *str)
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{
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int sign = 0;
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int prepend_zero = 0;
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int i, j, c, c1, c2;
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unsigned int nbits, nbytes, nlimbs;
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mpi_limb_t a;
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if (*str == '-') {
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sign = 1;
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str++;
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}
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/* Skip optional hex prefix. */
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if (*str == '0' && str[1] == 'x')
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str += 2;
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nbits = strlen(str);
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if (nbits > MAX_EXTERN_SCAN_BYTES) {
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mpi_clear(val);
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return -EINVAL;
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}
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nbits *= 4;
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if ((nbits % 8))
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prepend_zero = 1;
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nbytes = (nbits+7) / 8;
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nlimbs = (nbytes+BYTES_PER_MPI_LIMB-1) / BYTES_PER_MPI_LIMB;
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if (val->alloced < nlimbs)
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mpi_resize(val, nlimbs);
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i = BYTES_PER_MPI_LIMB - (nbytes % BYTES_PER_MPI_LIMB);
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i %= BYTES_PER_MPI_LIMB;
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j = val->nlimbs = nlimbs;
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val->sign = sign;
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for (; j > 0; j--) {
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a = 0;
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for (; i < BYTES_PER_MPI_LIMB; i++) {
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if (prepend_zero) {
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c1 = '0';
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prepend_zero = 0;
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} else
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c1 = *str++;
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if (!c1) {
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mpi_clear(val);
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return -EINVAL;
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}
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c2 = *str++;
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if (!c2) {
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mpi_clear(val);
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return -EINVAL;
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}
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if (c1 >= '0' && c1 <= '9')
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c = c1 - '0';
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else if (c1 >= 'a' && c1 <= 'f')
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c = c1 - 'a' + 10;
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else if (c1 >= 'A' && c1 <= 'F')
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c = c1 - 'A' + 10;
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else {
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mpi_clear(val);
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return -EINVAL;
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}
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c <<= 4;
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if (c2 >= '0' && c2 <= '9')
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c |= c2 - '0';
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else if (c2 >= 'a' && c2 <= 'f')
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c |= c2 - 'a' + 10;
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else if (c2 >= 'A' && c2 <= 'F')
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c |= c2 - 'A' + 10;
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else {
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mpi_clear(val);
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return -EINVAL;
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}
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a <<= 8;
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a |= c;
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}
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i = 0;
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val->d[j-1] = a;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(mpi_fromstr);
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MPI mpi_scanval(const char *string)
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{
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MPI a;
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a = mpi_alloc(0);
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if (!a)
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return NULL;
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if (mpi_fromstr(a, string)) {
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mpi_free(a);
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return NULL;
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}
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mpi_normalize(a);
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return a;
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}
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EXPORT_SYMBOL_GPL(mpi_scanval);
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static int count_lzeros(MPI a)
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{
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mpi_limb_t alimb;
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int i, lzeros = 0;
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for (i = a->nlimbs - 1; i >= 0; i--) {
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alimb = a->d[i];
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if (alimb == 0) {
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lzeros += sizeof(mpi_limb_t);
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} else {
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lzeros += count_leading_zeros(alimb) / 8;
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break;
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}
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}
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return lzeros;
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}
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/**
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* mpi_read_buffer() - read MPI to a buffer provided by user (msb first)
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*
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* @a: a multi precision integer
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* @buf: buffer to which the output will be written to. Needs to be at
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* least mpi_get_size(a) long.
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* @buf_len: size of the buf.
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* @nbytes: receives the actual length of the data written on success and
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* the data to-be-written on -EOVERFLOW in case buf_len was too
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* small.
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* @sign: if not NULL, it will be set to the sign of a.
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*
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* Return: 0 on success or error code in case of error
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*/
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int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
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int *sign)
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{
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uint8_t *p;
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#if BYTES_PER_MPI_LIMB == 4
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__be32 alimb;
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#elif BYTES_PER_MPI_LIMB == 8
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__be64 alimb;
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#else
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#error please implement for this limb size.
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#endif
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unsigned int n = mpi_get_size(a);
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int i, lzeros;
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if (!buf || !nbytes)
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return -EINVAL;
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if (sign)
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*sign = a->sign;
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lzeros = count_lzeros(a);
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if (buf_len < n - lzeros) {
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*nbytes = n - lzeros;
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return -EOVERFLOW;
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}
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p = buf;
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*nbytes = n - lzeros;
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for (i = a->nlimbs - 1 - lzeros / BYTES_PER_MPI_LIMB,
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lzeros %= BYTES_PER_MPI_LIMB;
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i >= 0; i--) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = cpu_to_be32(a->d[i]);
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = cpu_to_be64(a->d[i]);
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#else
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#error please implement for this limb size.
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#endif
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memcpy(p, (u8 *)&alimb + lzeros, BYTES_PER_MPI_LIMB - lzeros);
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p += BYTES_PER_MPI_LIMB - lzeros;
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lzeros = 0;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(mpi_read_buffer);
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/*
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* mpi_get_buffer() - Returns an allocated buffer with the MPI (msb first).
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* Caller must free the return string.
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* This function does return a 0 byte buffer with nbytes set to zero if the
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* value of A is zero.
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*
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* @a: a multi precision integer.
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* @nbytes: receives the length of this buffer.
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* @sign: if not NULL, it will be set to the sign of the a.
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*
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* Return: Pointer to MPI buffer or NULL on error
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*/
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void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign)
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{
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uint8_t *buf;
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unsigned int n;
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int ret;
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if (!nbytes)
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return NULL;
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n = mpi_get_size(a);
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if (!n)
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n++;
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buf = kmalloc(n, GFP_KERNEL);
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if (!buf)
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return NULL;
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ret = mpi_read_buffer(a, buf, n, nbytes, sign);
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if (ret) {
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kfree(buf);
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return NULL;
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}
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return buf;
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}
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EXPORT_SYMBOL_GPL(mpi_get_buffer);
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/**
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* mpi_write_to_sgl() - Funnction exports MPI to an sgl (msb first)
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*
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* This function works in the same way as the mpi_read_buffer, but it
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* takes an sgl instead of u8 * buf.
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*
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* @a: a multi precision integer
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* @sgl: scatterlist to write to. Needs to be at least
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* mpi_get_size(a) long.
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* @nbytes: the number of bytes to write. Leading bytes will be
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* filled with zero.
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* @sign: if not NULL, it will be set to the sign of a.
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*
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* Return: 0 on success or error code in case of error
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*/
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int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, unsigned nbytes,
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int *sign)
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{
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u8 *p, *p2;
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#if BYTES_PER_MPI_LIMB == 4
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__be32 alimb;
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#elif BYTES_PER_MPI_LIMB == 8
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__be64 alimb;
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#else
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#error please implement for this limb size.
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#endif
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unsigned int n = mpi_get_size(a);
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struct sg_mapping_iter miter;
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int i, x, buf_len;
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int nents;
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if (sign)
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*sign = a->sign;
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if (nbytes < n)
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return -EOVERFLOW;
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nents = sg_nents_for_len(sgl, nbytes);
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if (nents < 0)
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return -EINVAL;
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sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG);
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sg_miter_next(&miter);
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buf_len = miter.length;
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p2 = miter.addr;
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while (nbytes > n) {
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i = min_t(unsigned, nbytes - n, buf_len);
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memset(p2, 0, i);
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p2 += i;
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nbytes -= i;
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buf_len -= i;
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if (!buf_len) {
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sg_miter_next(&miter);
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buf_len = miter.length;
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p2 = miter.addr;
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}
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}
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for (i = a->nlimbs - 1; i >= 0; i--) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = a->d[i] ? cpu_to_be32(a->d[i]) : 0;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = a->d[i] ? cpu_to_be64(a->d[i]) : 0;
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#else
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#error please implement for this limb size.
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#endif
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p = (u8 *)&alimb;
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for (x = 0; x < sizeof(alimb); x++) {
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*p2++ = *p++;
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if (!--buf_len) {
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sg_miter_next(&miter);
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buf_len = miter.length;
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p2 = miter.addr;
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}
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}
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}
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sg_miter_stop(&miter);
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return 0;
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}
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EXPORT_SYMBOL_GPL(mpi_write_to_sgl);
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/*
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* mpi_read_raw_from_sgl() - Function allocates an MPI and populates it with
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* data from the sgl
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*
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* This function works in the same way as the mpi_read_raw_data, but it
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* takes an sgl instead of void * buffer. i.e. it allocates
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* a new MPI and reads the content of the sgl to the MPI.
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*
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* @sgl: scatterlist to read from
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* @nbytes: number of bytes to read
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*
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* Return: Pointer to a new MPI or NULL on error
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*/
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MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int nbytes)
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{
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struct sg_mapping_iter miter;
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unsigned int nbits, nlimbs;
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int x, j, z, lzeros, ents;
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unsigned int len;
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const u8 *buff;
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mpi_limb_t a;
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MPI val = NULL;
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ents = sg_nents_for_len(sgl, nbytes);
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if (ents < 0)
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return NULL;
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sg_miter_start(&miter, sgl, ents, SG_MITER_ATOMIC | SG_MITER_FROM_SG);
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lzeros = 0;
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len = 0;
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while (nbytes > 0) {
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while (len && !*buff) {
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lzeros++;
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len--;
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buff++;
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}
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if (len && *buff)
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break;
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sg_miter_next(&miter);
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buff = miter.addr;
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len = miter.length;
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nbytes -= lzeros;
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lzeros = 0;
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}
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miter.consumed = lzeros;
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nbytes -= lzeros;
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nbits = nbytes * 8;
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if (nbits > MAX_EXTERN_MPI_BITS) {
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sg_miter_stop(&miter);
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pr_info("MPI: mpi too large (%u bits)\n", nbits);
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return NULL;
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}
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if (nbytes > 0)
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nbits -= count_leading_zeros(*buff) - (BITS_PER_LONG - 8);
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sg_miter_stop(&miter);
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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val = mpi_alloc(nlimbs);
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if (!val)
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return NULL;
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val->nbits = nbits;
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val->sign = 0;
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val->nlimbs = nlimbs;
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if (nbytes == 0)
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return val;
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j = nlimbs - 1;
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a = 0;
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z = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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z %= BYTES_PER_MPI_LIMB;
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while (sg_miter_next(&miter)) {
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buff = miter.addr;
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len = min_t(unsigned, miter.length, nbytes);
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nbytes -= len;
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for (x = 0; x < len; x++) {
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a <<= 8;
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a |= *buff++;
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if (((z + x + 1) % BYTES_PER_MPI_LIMB) == 0) {
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val->d[j--] = a;
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a = 0;
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}
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}
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z += x;
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}
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return val;
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}
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EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);
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/* Perform a two's complement operation on buffer P of size N bytes. */
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static void twocompl(unsigned char *p, unsigned int n)
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{
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int i;
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for (i = n-1; i >= 0 && !p[i]; i--)
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;
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if (i >= 0) {
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if ((p[i] & 0x01))
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p[i] = (((p[i] ^ 0xfe) | 0x01) & 0xff);
|
|
else if ((p[i] & 0x02))
|
|
p[i] = (((p[i] ^ 0xfc) | 0x02) & 0xfe);
|
|
else if ((p[i] & 0x04))
|
|
p[i] = (((p[i] ^ 0xf8) | 0x04) & 0xfc);
|
|
else if ((p[i] & 0x08))
|
|
p[i] = (((p[i] ^ 0xf0) | 0x08) & 0xf8);
|
|
else if ((p[i] & 0x10))
|
|
p[i] = (((p[i] ^ 0xe0) | 0x10) & 0xf0);
|
|
else if ((p[i] & 0x20))
|
|
p[i] = (((p[i] ^ 0xc0) | 0x20) & 0xe0);
|
|
else if ((p[i] & 0x40))
|
|
p[i] = (((p[i] ^ 0x80) | 0x40) & 0xc0);
|
|
else
|
|
p[i] = 0x80;
|
|
|
|
for (i--; i >= 0; i--)
|
|
p[i] ^= 0xff;
|
|
}
|
|
}
|
|
|
|
int mpi_print(enum gcry_mpi_format format, unsigned char *buffer,
|
|
size_t buflen, size_t *nwritten, MPI a)
|
|
{
|
|
unsigned int nbits = mpi_get_nbits(a);
|
|
size_t len;
|
|
size_t dummy_nwritten;
|
|
int negative;
|
|
|
|
if (!nwritten)
|
|
nwritten = &dummy_nwritten;
|
|
|
|
/* Libgcrypt does no always care to set clear the sign if the value
|
|
* is 0. For printing this is a bit of a surprise, in particular
|
|
* because if some of the formats don't support negative numbers but
|
|
* should be able to print a zero. Thus we need this extra test
|
|
* for a negative number.
|
|
*/
|
|
if (a->sign && mpi_cmp_ui(a, 0))
|
|
negative = 1;
|
|
else
|
|
negative = 0;
|
|
|
|
len = buflen;
|
|
*nwritten = 0;
|
|
if (format == GCRYMPI_FMT_STD) {
|
|
unsigned char *tmp;
|
|
int extra = 0;
|
|
unsigned int n;
|
|
|
|
tmp = mpi_get_buffer(a, &n, NULL);
|
|
if (!tmp)
|
|
return -EINVAL;
|
|
|
|
if (negative) {
|
|
twocompl(tmp, n);
|
|
if (!(*tmp & 0x80)) {
|
|
/* Need to extend the sign. */
|
|
n++;
|
|
extra = 2;
|
|
}
|
|
} else if (n && (*tmp & 0x80)) {
|
|
/* Positive but the high bit of the returned buffer is set.
|
|
* Thus we need to print an extra leading 0x00 so that the
|
|
* output is interpreted as a positive number.
|
|
*/
|
|
n++;
|
|
extra = 1;
|
|
}
|
|
|
|
if (buffer && n > len) {
|
|
/* The provided buffer is too short. */
|
|
kfree(tmp);
|
|
return -E2BIG;
|
|
}
|
|
if (buffer) {
|
|
unsigned char *s = buffer;
|
|
|
|
if (extra == 1)
|
|
*s++ = 0;
|
|
else if (extra)
|
|
*s++ = 0xff;
|
|
memcpy(s, tmp, n-!!extra);
|
|
}
|
|
kfree(tmp);
|
|
*nwritten = n;
|
|
return 0;
|
|
} else if (format == GCRYMPI_FMT_USG) {
|
|
unsigned int n = (nbits + 7)/8;
|
|
|
|
/* Note: We ignore the sign for this format. */
|
|
/* FIXME: for performance reasons we should put this into
|
|
* mpi_aprint because we can then use the buffer directly.
|
|
*/
|
|
|
|
if (buffer && n > len)
|
|
return -E2BIG;
|
|
if (buffer) {
|
|
unsigned char *tmp;
|
|
|
|
tmp = mpi_get_buffer(a, &n, NULL);
|
|
if (!tmp)
|
|
return -EINVAL;
|
|
memcpy(buffer, tmp, n);
|
|
kfree(tmp);
|
|
}
|
|
*nwritten = n;
|
|
return 0;
|
|
} else if (format == GCRYMPI_FMT_PGP) {
|
|
unsigned int n = (nbits + 7)/8;
|
|
|
|
/* The PGP format can only handle unsigned integers. */
|
|
if (negative)
|
|
return -EINVAL;
|
|
|
|
if (buffer && n+2 > len)
|
|
return -E2BIG;
|
|
|
|
if (buffer) {
|
|
unsigned char *tmp;
|
|
unsigned char *s = buffer;
|
|
|
|
s[0] = nbits >> 8;
|
|
s[1] = nbits;
|
|
|
|
tmp = mpi_get_buffer(a, &n, NULL);
|
|
if (!tmp)
|
|
return -EINVAL;
|
|
memcpy(s+2, tmp, n);
|
|
kfree(tmp);
|
|
}
|
|
*nwritten = n+2;
|
|
return 0;
|
|
} else if (format == GCRYMPI_FMT_SSH) {
|
|
unsigned char *tmp;
|
|
int extra = 0;
|
|
unsigned int n;
|
|
|
|
tmp = mpi_get_buffer(a, &n, NULL);
|
|
if (!tmp)
|
|
return -EINVAL;
|
|
|
|
if (negative) {
|
|
twocompl(tmp, n);
|
|
if (!(*tmp & 0x80)) {
|
|
/* Need to extend the sign. */
|
|
n++;
|
|
extra = 2;
|
|
}
|
|
} else if (n && (*tmp & 0x80)) {
|
|
n++;
|
|
extra = 1;
|
|
}
|
|
|
|
if (buffer && n+4 > len) {
|
|
kfree(tmp);
|
|
return -E2BIG;
|
|
}
|
|
|
|
if (buffer) {
|
|
unsigned char *s = buffer;
|
|
|
|
*s++ = n >> 24;
|
|
*s++ = n >> 16;
|
|
*s++ = n >> 8;
|
|
*s++ = n;
|
|
if (extra == 1)
|
|
*s++ = 0;
|
|
else if (extra)
|
|
*s++ = 0xff;
|
|
memcpy(s, tmp, n-!!extra);
|
|
}
|
|
kfree(tmp);
|
|
*nwritten = 4+n;
|
|
return 0;
|
|
} else if (format == GCRYMPI_FMT_HEX) {
|
|
unsigned char *tmp;
|
|
int i;
|
|
int extra = 0;
|
|
unsigned int n = 0;
|
|
|
|
tmp = mpi_get_buffer(a, &n, NULL);
|
|
if (!tmp)
|
|
return -EINVAL;
|
|
if (!n || (*tmp & 0x80))
|
|
extra = 2;
|
|
|
|
if (buffer && 2*n + extra + negative + 1 > len) {
|
|
kfree(tmp);
|
|
return -E2BIG;
|
|
}
|
|
if (buffer) {
|
|
unsigned char *s = buffer;
|
|
|
|
if (negative)
|
|
*s++ = '-';
|
|
if (extra) {
|
|
*s++ = '0';
|
|
*s++ = '0';
|
|
}
|
|
|
|
for (i = 0; i < n; i++) {
|
|
unsigned int c = tmp[i];
|
|
|
|
*s++ = (c >> 4) < 10 ? '0'+(c>>4) : 'A'+(c>>4)-10;
|
|
c &= 15;
|
|
*s++ = c < 10 ? '0'+c : 'A'+c-10;
|
|
}
|
|
*s++ = 0;
|
|
*nwritten = s - buffer;
|
|
} else {
|
|
*nwritten = 2*n + extra + negative + 1;
|
|
}
|
|
kfree(tmp);
|
|
return 0;
|
|
} else
|
|
return -EINVAL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mpi_print);
|