forked from mirrors/linux
60e1b74c22
In mpi_read_raw_from_sgl(), unsigned nbits is calculated as follows:
nbits = nbytes * 8;
and redundantly cleared later on if nbytes == 0:
if (nbytes > 0)
...
else
nbits = 0;
Purge this redundant clearing for the sake of clarity.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
505 lines
11 KiB
C
505 lines
11 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/string.h>
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#include "mpi-internal.h"
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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]);
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else
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nbits = 0;
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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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int i, j;
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unsigned nbits, nbytes, nlimbs, nread = 0;
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mpi_limb_t a;
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MPI val = NULL;
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if (*ret_nread < 2)
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goto leave;
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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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goto leave;
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}
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buffer += 2;
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nread = 2;
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nbytes = DIV_ROUND_UP(nbits, 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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i = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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i %= BYTES_PER_MPI_LIMB;
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val->nbits = nbits;
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j = val->nlimbs = nlimbs;
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val->sign = 0;
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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 (++nread > *ret_nread) {
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printk
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("MPI: mpi larger than buffer nread=%d ret_nread=%d\n",
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nread, *ret_nread);
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goto leave;
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}
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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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leave:
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*ret_nread = nread;
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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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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 bufer provided by user (msb first)
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*
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* @a: a multi precision integer
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* @buf: bufer to which the output will be written to. Needs to be at
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* leaset 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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* Use BUFFER to update MPI.
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*/
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int mpi_set_buffer(MPI a, const void *xbuffer, unsigned nbytes, int sign)
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{
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const uint8_t *buffer = xbuffer, *p;
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mpi_limb_t alimb;
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int nlimbs;
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int i;
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nlimbs = DIV_ROUND_UP(nbytes, BYTES_PER_MPI_LIMB);
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if (RESIZE_IF_NEEDED(a, nlimbs) < 0)
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return -ENOMEM;
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a->sign = sign;
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for (i = 0, p = buffer + nbytes - 1; p >= buffer + BYTES_PER_MPI_LIMB;) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = (mpi_limb_t) *p--;
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alimb |= (mpi_limb_t) *p-- << 8;
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alimb |= (mpi_limb_t) *p-- << 16;
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alimb |= (mpi_limb_t) *p-- << 24;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = (mpi_limb_t) *p--;
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alimb |= (mpi_limb_t) *p-- << 8;
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alimb |= (mpi_limb_t) *p-- << 16;
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alimb |= (mpi_limb_t) *p-- << 24;
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alimb |= (mpi_limb_t) *p-- << 32;
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alimb |= (mpi_limb_t) *p-- << 40;
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alimb |= (mpi_limb_t) *p-- << 48;
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alimb |= (mpi_limb_t) *p-- << 56;
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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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a->d[i++] = alimb;
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}
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if (p >= buffer) {
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#if BYTES_PER_MPI_LIMB == 4
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alimb = *p--;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 8;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 16;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 24;
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#elif BYTES_PER_MPI_LIMB == 8
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alimb = (mpi_limb_t) *p--;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 8;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 16;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 24;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 32;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 40;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 48;
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if (p >= buffer)
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alimb |= (mpi_limb_t) *p-- << 56;
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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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a->d[i++] = alimb;
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}
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a->nlimbs = i;
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if (i != nlimbs) {
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pr_emerg("MPI: mpi_set_buffer: Assertion failed (%d != %d)", i,
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nlimbs);
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BUG();
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(mpi_set_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: in/out param - it has the be set to the maximum number of
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* bytes that can be written to sgl. This has to be at least
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* the size of the integer a. On return it receives the actual
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* length of the data written on success or the data that would
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* be written if buffer was too 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_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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int i, x, y = 0, lzeros, buf_len;
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if (!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 (*nbytes < n - lzeros) {
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*nbytes = n - lzeros;
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return -EOVERFLOW;
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}
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*nbytes = n - lzeros;
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buf_len = sgl->length;
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p2 = sg_virt(sgl);
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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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if (lzeros) {
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y = lzeros;
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lzeros = 0;
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}
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p = (u8 *)&alimb + y;
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for (x = 0; x < sizeof(alimb) - y; x++) {
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if (!buf_len) {
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sgl = sg_next(sgl);
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if (!sgl)
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return -EINVAL;
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buf_len = sgl->length;
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p2 = sg_virt(sgl);
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}
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*p2++ = *p++;
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buf_len--;
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}
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y = 0;
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}
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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 scatterlist *sg;
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int x, i, j, z, lzeros, ents;
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unsigned int nbits, nlimbs;
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mpi_limb_t a;
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MPI val = NULL;
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lzeros = 0;
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ents = sg_nents(sgl);
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for_each_sg(sgl, sg, ents, i) {
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const u8 *buff = sg_virt(sg);
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int len = sg->length;
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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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ents--;
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nbytes -= lzeros;
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lzeros = 0;
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}
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sgl = sg;
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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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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(*(u8 *)(sg_virt(sgl) + lzeros));
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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 = 0;
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x = BYTES_PER_MPI_LIMB - nbytes % BYTES_PER_MPI_LIMB;
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x %= BYTES_PER_MPI_LIMB;
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for_each_sg(sgl, sg, ents, i) {
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const u8 *buffer = sg_virt(sg) + lzeros;
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int len = sg->length - lzeros;
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int buf_shift = x;
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if (sg_is_last(sg) && (len % BYTES_PER_MPI_LIMB))
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len += BYTES_PER_MPI_LIMB - (len % BYTES_PER_MPI_LIMB);
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for (; x < len + buf_shift; x++) {
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a <<= 8;
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a |= *buffer++;
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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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x = 0;
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lzeros = 0;
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}
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return val;
|
|
}
|
|
EXPORT_SYMBOL_GPL(mpi_read_raw_from_sgl);
|