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H A Djitterentropy.cdiff 59bcfd788552504606e3eb774ae68052379396b6 Thu Sep 21 13:48:33 CEST 2023 Stephan Müller <smueller@chronox.de> crypto: jitter - Allow configuration of memory size

The memory size consumed by the Jitter RNG is one contributing factor in
the amount of entropy that is gathered. As the amount of entropy
directly correlates with the distance of the memory from the CPU, the
caches that are possibly present on a given system have an impact on the
collected entropy.

Thus, the kernel compile time should offer a means to configure the
amount of memory used by the Jitter RNG. Although this option could be
turned into a runtime option (e.g. a kernel command line option), it
should remain a compile time option as otherwise adminsitrators who may
not have performed an entropy assessment may select a value that is
inappropriate.

The default value selected by the configuration is identical to the
current Jitter RNG value. Thus, the patch should not lead to any change
in the Jitter RNG behavior.

To accommodate larger memory buffers, kvzalloc / kvfree is used.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
H A Djitterentropy-kcapi.cdiff 59bcfd788552504606e3eb774ae68052379396b6 Thu Sep 21 13:48:33 CEST 2023 Stephan Müller <smueller@chronox.de> crypto: jitter - Allow configuration of memory size

The memory size consumed by the Jitter RNG is one contributing factor in
the amount of entropy that is gathered. As the amount of entropy
directly correlates with the distance of the memory from the CPU, the
caches that are possibly present on a given system have an impact on the
collected entropy.

Thus, the kernel compile time should offer a means to configure the
amount of memory used by the Jitter RNG. Although this option could be
turned into a runtime option (e.g. a kernel command line option), it
should remain a compile time option as otherwise adminsitrators who may
not have performed an entropy assessment may select a value that is
inappropriate.

The default value selected by the configuration is identical to the
current Jitter RNG value. Thus, the patch should not lead to any change
in the Jitter RNG behavior.

To accommodate larger memory buffers, kvzalloc / kvfree is used.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>