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path: root/arch/s390/crypto/arch_random.c
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2018-05-30s390/archrandom: Rework arch random implementation.Harald Freudenberger
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>
2017-11-24s390: crypto: Remove redundant license textGreg Kroah-Hartman
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>
2017-11-24s390: crypto: add SPDX identifiers to the remaining filesGreg Kroah-Hartman
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>
2017-06-12s390: add missing header includes for type checkingHeiko Carstens
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>
2017-04-26s390/crypto: Provide s390 specific arch random functionality.Harald Freudenberger
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>