diff options
| -rw-r--r-- | arch/s390/crypto/arch_random.c | 103 | ||||
| -rw-r--r-- | arch/s390/include/asm/archrandom.h | 13 |
2 files changed, 102 insertions, 14 deletions
diff --git a/arch/s390/crypto/arch_random.c b/arch/s390/crypto/arch_random.c index 8720e9203ecf..dd95cdbd22ce 100644 --- a/arch/s390/crypto/arch_random.c +++ b/arch/s390/crypto/arch_random.c @@ -2,14 +2,37 @@ /* * s390 arch random implementation. * - * Copyright IBM Corp. 2017 - * Author(s): Harald Freudenberger <freude@de.ibm.com> + * Copyright IBM Corp. 2017, 2018 + * Author(s): Harald Freudenberger + * + * The s390_arch_random_generate() function may be called from random.c + * in interrupt context. So this implementation does the best to be very + * fast. There is a buffer of random data which is asynchronously checked + * and filled 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 PRNG. + * 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 4k bytes per second. */ #include <linux/kernel.h> #include <linux/atomic.h> #include <linux/random.h> +#include <linux/slab.h> #include <linux/static_key.h> +#include <linux/workqueue.h> #include <asm/cpacf.h> DEFINE_STATIC_KEY_FALSE(s390_arch_random_available); @@ -17,11 +40,83 @@ DEFINE_STATIC_KEY_FALSE(s390_arch_random_available); atomic64_t s390_arch_random_counter = ATOMIC64_INIT(0); EXPORT_SYMBOL(s390_arch_random_counter); +#define ARCH_REFILL_TICKS (HZ/2) +#define ARCH_PRNG_SEED_SIZE 32 +#define ARCH_RNG_BUF_SIZE 2048 + +static DEFINE_SPINLOCK(arch_rng_lock); +static u8 *arch_rng_buf; +static unsigned int arch_rng_buf_idx; + +static void arch_rng_refill_buffer(struct work_struct *); +static DECLARE_DELAYED_WORK(arch_rng_work, arch_rng_refill_buffer); + +bool s390_arch_random_generate(u8 *buf, unsigned int nbytes) +{ + /* lock rng buffer */ + if (!spin_trylock(&arch_rng_lock)) + return false; + + /* try to resolve the requested amount of bytes from the buffer */ + arch_rng_buf_idx -= nbytes; + if (arch_rng_buf_idx < ARCH_RNG_BUF_SIZE) { + memcpy(buf, arch_rng_buf + arch_rng_buf_idx, nbytes); + atomic64_add(nbytes, &s390_arch_random_counter); + spin_unlock(&arch_rng_lock); + return true; + } + + /* not enough bytes in rng buffer, refill is done asynchronously */ + spin_unlock(&arch_rng_lock); + + return false; +} +EXPORT_SYMBOL(s390_arch_random_generate); + +static void arch_rng_refill_buffer(struct work_struct *unused) +{ + unsigned int delay = ARCH_REFILL_TICKS; + + spin_lock(&arch_rng_lock); + if (arch_rng_buf_idx > ARCH_RNG_BUF_SIZE) { + /* buffer is exhausted and needs refill */ + u8 seed[ARCH_PRNG_SEED_SIZE]; + u8 prng_wa[240]; + /* fetch ARCH_PRNG_SEED_SIZE bytes of entropy */ + cpacf_trng(NULL, 0, seed, sizeof(seed)); + /* blow this entropy up to ARCH_RNG_BUF_SIZE with PRNG */ + memset(prng_wa, 0, sizeof(prng_wa)); + cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, + &prng_wa, NULL, 0, seed, sizeof(seed)); + cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, + &prng_wa, arch_rng_buf, ARCH_RNG_BUF_SIZE, NULL, 0); + arch_rng_buf_idx = ARCH_RNG_BUF_SIZE; + } + delay += (ARCH_REFILL_TICKS * arch_rng_buf_idx) / ARCH_RNG_BUF_SIZE; + spin_unlock(&arch_rng_lock); + + /* kick next check */ + queue_delayed_work(system_long_wq, &arch_rng_work, delay); +} + static int __init s390_arch_random_init(void) { - /* check if subfunction CPACF_PRNO_TRNG is available */ - if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) + /* all the needed PRNO subfunctions available ? */ + if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG) && + cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN)) { + + /* alloc arch random working buffer */ + arch_rng_buf = kmalloc(ARCH_RNG_BUF_SIZE, GFP_KERNEL); + if (!arch_rng_buf) + return -ENOMEM; + + /* kick worker queue job to fill the random buffer */ + queue_delayed_work(system_long_wq, + &arch_rng_work, ARCH_REFILL_TICKS); + + /* enable arch random to the outside world */ static_branch_enable(&s390_arch_random_available); + } return 0; } diff --git a/arch/s390/include/asm/archrandom.h b/arch/s390/include/asm/archrandom.h index 09aed1095336..c67b82dfa558 100644 --- a/arch/s390/include/asm/archrandom.h +++ b/arch/s390/include/asm/archrandom.h @@ -15,16 +15,11 @@ #include <linux/static_key.h> #include <linux/atomic.h> -#include <asm/cpacf.h> DECLARE_STATIC_KEY_FALSE(s390_arch_random_available); extern atomic64_t s390_arch_random_counter; -static void s390_arch_random_generate(u8 *buf, unsigned int nbytes) -{ - cpacf_trng(NULL, 0, buf, nbytes); - atomic64_add(nbytes, &s390_arch_random_counter); -} +bool s390_arch_random_generate(u8 *buf, unsigned int nbytes); static inline bool arch_has_random(void) { @@ -51,8 +46,7 @@ static inline bool arch_get_random_int(unsigned int *v) static inline bool arch_get_random_seed_long(unsigned long *v) { if (static_branch_likely(&s390_arch_random_available)) { - s390_arch_random_generate((u8 *)v, sizeof(*v)); - return true; + return s390_arch_random_generate((u8 *)v, sizeof(*v)); } return false; } @@ -60,8 +54,7 @@ static inline bool arch_get_random_seed_long(unsigned long *v) static inline bool arch_get_random_seed_int(unsigned int *v) { if (static_branch_likely(&s390_arch_random_available)) { - s390_arch_random_generate((u8 *)v, sizeof(*v)); - return true; + return s390_arch_random_generate((u8 *)v, sizeof(*v)); } return false; } |