forked from Minki/linux
01c9348c76
The hardware RNG on POWER8 and POWER7+ can be relatively slow, since
it can only supply one 64-bit value per microsecond. Currently we
read it in arch_get_random_long(), but that slows down reading from
/dev/urandom since the code in random.c calls arch_get_random_long()
for every longword read from /dev/urandom.
Since the hardware RNG supplies high-quality entropy on every read, it
matches the semantics of arch_get_random_seed_long() better than those
of arch_get_random_long(). Therefore this commit makes the code use
the POWER8/7+ hardware RNG only for arch_get_random_seed_{long,int}
and not for arch_get_random_{long,int}.
This won't affect any other PowerPC-based platforms because none of
them currently support a hardware RNG. To make it clear that the
ppc_md function pointer is used for arch_get_random_seed_*, we rename
it from get_random_long to get_random_seed.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
46 lines
994 B
C
46 lines
994 B
C
/*
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* Copyright 2013, Michael Ellerman, IBM Corporation.
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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
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#define pr_fmt(fmt) "pseries-rng: " fmt
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#include <linux/kernel.h>
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#include <linux/of.h>
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#include <asm/archrandom.h>
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#include <asm/machdep.h>
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#include <asm/plpar_wrappers.h>
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static int pseries_get_random_long(unsigned long *v)
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{
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unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
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if (plpar_hcall(H_RANDOM, retbuf) == H_SUCCESS) {
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*v = retbuf[0];
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return 1;
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}
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return 0;
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}
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static __init int rng_init(void)
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{
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struct device_node *dn;
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dn = of_find_compatible_node(NULL, NULL, "ibm,random");
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if (!dn)
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return -ENODEV;
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pr_info("Registering arch random hook.\n");
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ppc_md.get_random_seed = pseries_get_random_long;
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return 0;
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}
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machine_subsys_initcall(pseries, rng_init);
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