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powerpc: Use hardware RNG for arch_get_random_seed_* not arch_get_random_*
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>
This commit is contained in:
parent
1c2cb59444
commit
01c9348c76
4 changed files with 17 additions and 17 deletions
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@ -7,13 +7,22 @@
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static inline int arch_get_random_long(unsigned long *v)
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{
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if (ppc_md.get_random_long)
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return ppc_md.get_random_long(v);
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return 0;
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}
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static inline int arch_get_random_int(unsigned int *v)
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{
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return 0;
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}
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static inline int arch_get_random_seed_long(unsigned long *v)
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{
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if (ppc_md.get_random_seed)
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return ppc_md.get_random_seed(v);
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return 0;
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}
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static inline int arch_get_random_seed_int(unsigned int *v)
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{
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unsigned long val;
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int rc;
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@ -27,22 +36,13 @@ static inline int arch_get_random_int(unsigned int *v)
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static inline int arch_has_random(void)
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{
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return !!ppc_md.get_random_long;
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return 0;
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}
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static inline int arch_get_random_seed_long(unsigned long *v)
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{
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return 0;
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}
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static inline int arch_get_random_seed_int(unsigned int *v)
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{
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return 0;
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}
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static inline int arch_has_random_seed(void)
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{
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return 0;
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return !!ppc_md.get_random_seed;
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}
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#endif /* CONFIG_ARCH_RANDOM */
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#ifdef CONFIG_PPC_POWERNV
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@ -249,7 +249,7 @@ struct machdep_calls {
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#endif
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#ifdef CONFIG_ARCH_RANDOM
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int (*get_random_long)(unsigned long *v);
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int (*get_random_seed)(unsigned long *v);
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#endif
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};
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@ -128,7 +128,7 @@ static __init int rng_create(struct device_node *dn)
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pr_info_once("Registering arch random hook.\n");
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ppc_md.get_random_long = powernv_get_random_long;
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ppc_md.get_random_seed = powernv_get_random_long;
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return 0;
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}
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@ -38,7 +38,7 @@ static __init int rng_init(void)
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pr_info("Registering arch random hook.\n");
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ppc_md.get_random_long = pseries_get_random_long;
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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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