mirror of
https://github.com/ipxe/ipxe
synced 2026-06-29 00:07:28 +03:00
Michael Brown
e5d0c804ee
The "prno" instruction available on newer CPUs provides a hardware True Random Number Generator (TRNG) that can be used as an entropy source, similar to the x86 "rdrand" instruction. Signed-off-by: Michael Brown <mcb30@ipxe.org>
125 lines
3.5 KiB
C
125 lines
3.5 KiB
C
/*
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* Copyright (C) 2026 Michael Brown <mbrown@fensystems.co.uk>.
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*
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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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*
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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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*
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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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* 02110-1301, USA.
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*
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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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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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/** @file
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*
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* Perform Random Number Operation (PRNO) entropy source
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*
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*/
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#include <errno.h>
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#include <ipxe/entropy.h>
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#include <ipxe/facility.h>
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#include <ipxe/prno.h>
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struct entropy_source prno_entropy __entropy_source ( ENTROPY_PREFERRED );
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/** Colour for debug messages */
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#define colour &prno_entropy
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/**
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* Enable entropy gathering
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*
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* @ret rc Return status code
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*/
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static int prno_entropy_enable ( void ) {
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union prno_parameters params;
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struct s390x_scalar_pair dummy1;
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struct s390x_scalar_pair dummy2;
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register unsigned long fn asm ( "0" );
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register void *pp asm ( "1" );
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/* Check if PRNO is supported */
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if ( ! facility_is_installed ( FACILITY_MSA5 ) ) {
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DBGC ( colour, "PRNO instruction is not supported\n" );
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return -ENOTSUP;
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}
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DBGC ( colour, "PRNO instruction is supported\n" );
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/* Check if TRNG is supported */
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__asm__ ( ".machine push\n\t"
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".machine \"z14\"\n\t"
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"prno %2, %3\n\t"
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".machine pop\n\t"
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: "=r" ( fn ),
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"=r" ( pp ),
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"=a" ( dummy1 ),
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"=a" ( dummy2 ),
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"=m" ( params )
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: "0" ( PRNO_FN_QUERY ),
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"1" ( ¶ms ) );
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if ( ! prno_is_supported ( ¶ms.supported, PRNO_FN_TRNG ) ) {
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DBGC ( colour, "PRNO does not support TRNG (%016llx:%016llx)\n",
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params.supported.mask[0], params.supported.mask[1] );
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return -ENOTSUP;
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}
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DBGC ( colour, "PRNO has support for TRNG\n" );
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/* Linux assumes that the TRNG produces 100% entropy. Nothing
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* seems to actually guarantee this, and we don't need much
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* entropy, so assume conservatively that each byte contains
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* at least one bit of min-entropy.
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*/
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entropy_init ( &prno_entropy, MIN_ENTROPY ( 1.0 ) );
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return 0;
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}
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/**
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* Get noise sample
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*
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* @ret noise Noise sample
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* @ret rc Return status code
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*/
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static int prno_get_noise ( noise_sample_t *noise ) {
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struct s390x_pointer_pair raw = { noise, sizeof ( *noise ) };
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struct s390x_pointer_pair conditioned = { NULL, 0 };
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register unsigned long fn asm ( "0" );
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register void *pp asm ( "1" );
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/* Generate raw true random numbers */
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__asm__ ( ".machine push\n\t"
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".machine \"z14\"\n\t"
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"\n1:\n\t"
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"prno %2, %3\n\t"
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"jo 1b\n\t"
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".machine pop\n\t"
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: "=r" ( fn ),
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"=r" ( pp ),
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"+a" ( raw ),
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"+a" ( conditioned ),
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"=m" ( *noise )
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: "0" ( PRNO_FN_TRNG ) );
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return 0;
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}
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/** Hardware entropy source */
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struct entropy_source prno_entropy __entropy_source ( ENTROPY_PREFERRED ) = {
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.name = "prno",
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.enable = prno_entropy_enable,
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.get_noise = prno_get_noise,
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};
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