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The arch_get_random_seed_long() invocation done by the random device
driver is done in interrupt context and may be invoked very very
frequently. The existing s390 arch_get_random_seed*() implementation
uses the PRNO(TRNG) instruction which produces excellent high quality
entropy but is relatively slow and thus expensive.
This fix reworks the arch_get_random_seed* implementation. It
introduces a buffer concept to decouple the delivery of random data
via arch_get_random_seed*() from the generation of new random
bytes. The buffer of random data is filled asynchronously by a
workqueue thread.
If there are enough bytes in the buffer the s390_arch_random_generate()
just delivers these bytes. Otherwise false is returned until the worker
thread refills the buffer.
The worker fills the rng buffer by pulling fresh entropy from the
high quality (but slow) true hardware random generator. This entropy
is then spread over the buffer with an pseudo random generator.
As the arch_get_random_seed_long() fetches 8 bytes and the calling
function add_interrupt_randomness() counts this as 1 bit entropy the
distribution needs to make sure there is in fact 1 bit entropy
contained in 8 bytes of the buffer. The current values pull 32 byte
entropy and scatter this into a 2048 byte buffer. So 8 byte in the
buffer will contain 1 bit of entropy.
The worker thread is rescheduled based on the charge level of the
buffer but at least with 500 ms delay to avoid too much cpu consumption.
So the max. amount of rng data delivered via arch_get_random_seed is
limited to 4Kb per second.
Signed-off-by: Harald Freudenberger <freude@de.ibm.com>
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Now that the SPDX tag is in all arch/s390/crypto/ files, that identifies
the license in a specific and legally-defined manner. So the extra GPL
text wording can be removed as it is no longer needed at all.
This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text. And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.
No copyright headers or other non-license-description text was removed.
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.
Update the arch/s390/crypto/ files with the correct SPDX license
identifier based on the license text in the file itself. The SPDX
identifier is a legally binding shorthand, which can be used instead of
the full boiler plate text.
This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Add missing include statements to make sure that prototypes match
implementation. As reported by sparse:
arch/s390/crypto/arch_random.c:18:1:
warning: symbol 's390_arch_random_available' was not declared. Should it be static?
arch/s390/kernel/traps.c:279:13: warning:
symbol 'trap_init' was not declared. Should it be static?
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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This patch introduces s390 specific arch random functionality.
There exists a generic kernel API for arch specific random
number implementation (see include/linux/random.h). Here
comes the header file and a very small static code part
implementing the arch_random_* API based on the TRNG
subfunction coming with the reworked PRNG instruction.
The arch random implementation hooks into the kernel
initialization and checks for availability of the TRNG
function. In accordance to the arch random API all functions
return false if the TRNG is not available. Otherwise the new
high quality entropy source provides fresh random on each
invocation.
The s390 arch random feature build is controlled via
CONFIG_ARCH_RANDOM. This config option located in
arch/s390/Kconfig is enabled by default and appears
as entry "s390 architectural random number generation API"
in the submenu "Processor type and features" for s390 builds.
Signed-off-by: Harald Freudenberger <freude@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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