diff options
Diffstat (limited to 'arch/s390/crypto/arch_random.c')
| -rw-r--r-- | arch/s390/crypto/arch_random.c | 111 |
1 files changed, 1 insertions, 110 deletions
diff --git a/arch/s390/crypto/arch_random.c b/arch/s390/crypto/arch_random.c index 4cbb4b6d85a8..1f2d40993c4d 100644 --- a/arch/s390/crypto/arch_random.c +++ b/arch/s390/crypto/arch_random.c @@ -2,126 +2,17 @@ /* * s390 arch random implementation. * - * Copyright IBM Corp. 2017, 2018 + * Copyright IBM Corp. 2017, 2020 * 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); 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) -{ - /* max hunk is ARCH_RNG_BUF_SIZE */ - if (nbytes > ARCH_RNG_BUF_SIZE) - return false; - - /* 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) -{ - /* 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; -} -arch_initcall(s390_arch_random_init); |