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* Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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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., 51 Franklin Street, Fifth Floor, Boston, MA
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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* Linux entropy source
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#include <linux_api.h>
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#include <ipxe/entropy.h>
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/** Entropy source filename */
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static const char entropy_filename[] = "/dev/random";
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/** Entropy source file handle */
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static int entropy_fd;
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* Enable entropy gathering
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* @ret rc Return status code
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static int linux_entropy_enable ( void ) {
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/* Open entropy source */
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entropy_fd = linux_open ( entropy_filename, O_RDONLY );
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if ( entropy_fd < 0 ) {
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DBGC ( &entropy_fd, "ENTROPY could not open %s: %s\n",
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entropy_filename, linux_strerror ( linux_errno ) );
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* Disable entropy gathering
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static void linux_entropy_disable ( void ) {
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/* Close entropy source */
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linux_close ( entropy_fd );
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* @ret noise Noise sample
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* @ret rc Return status code
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static int linux_get_noise ( noise_sample_t *noise ) {
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/* Read a single byte from entropy source */
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len = linux_read ( entropy_fd, &byte, sizeof ( byte ) );
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DBGC ( &entropy_fd, "ENTROPY could not read from %s: %s\n",
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entropy_filename, linux_strerror ( linux_errno ) );
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DBGC ( &entropy_fd, "ENTROPY EOF on reading from %s: %s\n",
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entropy_filename, linux_strerror ( linux_errno ) );
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PROVIDE_ENTROPY_INLINE ( linux, min_entropy_per_sample );
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PROVIDE_ENTROPY ( linux, entropy_enable, linux_entropy_enable );
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PROVIDE_ENTROPY ( linux, entropy_disable, linux_entropy_disable );
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PROVIDE_ENTROPY ( linux, get_noise, linux_get_noise );