diff options
| -rw-r--r-- | drivers/char/random.c | 114 |
1 files changed, 20 insertions, 94 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c index 9014fd54da64..20538e9b1a2c 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -286,17 +286,9 @@ /* #define ADD_INTERRUPT_BENCH */ -enum poolinfo { +enum { POOL_BITS = BLAKE2S_HASH_SIZE * 8, - POOL_BITSHIFT = ilog2(POOL_BITS), - POOL_MIN_BITS = POOL_BITS / 2, - - /* To allow fractional bits to be tracked, the entropy_count field is - * denominated in units of 1/8th bits. */ - POOL_ENTROPY_SHIFT = 3, -#define POOL_ENTROPY_BITS() (input_pool.entropy_count >> POOL_ENTROPY_SHIFT) - POOL_FRACBITS = POOL_BITS << POOL_ENTROPY_SHIFT, - POOL_MIN_FRACBITS = POOL_MIN_BITS << POOL_ENTROPY_SHIFT + POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */ }; /* @@ -309,7 +301,7 @@ static struct fasync_struct *fasync; * should wake up processes which are selecting or polling on write * access to /dev/random. */ -static int random_write_wakeup_bits = POOL_BITS * 3 / 4; +static int random_write_wakeup_bits = POOL_MIN_BITS; static DEFINE_SPINLOCK(random_ready_list_lock); static LIST_HEAD(random_ready_list); @@ -469,66 +461,18 @@ static void process_random_ready_list(void) static void credit_entropy_bits(int nbits) { int entropy_count, orig; - int nfrac = nbits << POOL_ENTROPY_SHIFT; - - /* Ensure that the multiplication can avoid being 64 bits wide. */ - BUILD_BUG_ON(2 * (POOL_ENTROPY_SHIFT + POOL_BITSHIFT) > 31); if (!nbits) return; -retry: - entropy_count = orig = READ_ONCE(input_pool.entropy_count); - if (nfrac < 0) { - /* Debit */ - entropy_count += nfrac; - } else { - /* - * Credit: we have to account for the possibility of - * overwriting already present entropy. Even in the - * ideal case of pure Shannon entropy, new contributions - * approach the full value asymptotically: - * - * entropy <- entropy + (pool_size - entropy) * - * (1 - exp(-add_entropy/pool_size)) - * - * For add_entropy <= pool_size/2 then - * (1 - exp(-add_entropy/pool_size)) >= - * (add_entropy/pool_size)*0.7869... - * so we can approximate the exponential with - * 3/4*add_entropy/pool_size and still be on the - * safe side by adding at most pool_size/2 at a time. - * - * The use of pool_size-2 in the while statement is to - * prevent rounding artifacts from making the loop - * arbitrarily long; this limits the loop to log2(pool_size)*2 - * turns no matter how large nbits is. - */ - int pnfrac = nfrac; - const int s = POOL_BITSHIFT + POOL_ENTROPY_SHIFT + 2; - /* The +2 corresponds to the /4 in the denominator */ - - do { - unsigned int anfrac = min(pnfrac, POOL_FRACBITS / 2); - unsigned int add = - ((POOL_FRACBITS - entropy_count) * anfrac * 3) >> s; - - entropy_count += add; - pnfrac -= anfrac; - } while (unlikely(entropy_count < POOL_FRACBITS - 2 && pnfrac)); - } - - if (WARN_ON(entropy_count < 0)) { - pr_warn("negative entropy/overflow: count %d\n", entropy_count); - entropy_count = 0; - } else if (entropy_count > POOL_FRACBITS) - entropy_count = POOL_FRACBITS; - if (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig) - goto retry; + do { + orig = READ_ONCE(input_pool.entropy_count); + entropy_count = min(POOL_BITS, orig + nbits); + } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); - trace_credit_entropy_bits(nbits, entropy_count >> POOL_ENTROPY_SHIFT, _RET_IP_); + trace_credit_entropy_bits(nbits, entropy_count, _RET_IP_); - if (crng_init < 2 && entropy_count >= POOL_MIN_FRACBITS) + if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) crng_reseed(&primary_crng, true); } @@ -791,7 +735,7 @@ static void crng_reseed(struct crng_state *crng, bool use_input_pool) int entropy_count; do { entropy_count = READ_ONCE(input_pool.entropy_count); - if (entropy_count < POOL_MIN_FRACBITS) + if (entropy_count < POOL_MIN_BITS) return; } while (cmpxchg(&input_pool.entropy_count, entropy_count, 0) != entropy_count); extract_entropy(buf.key, sizeof(buf.key)); @@ -1014,7 +958,7 @@ void add_input_randomness(unsigned int type, unsigned int code, last_value = value; add_timer_randomness(&input_timer_state, (type << 4) ^ code ^ (code >> 4) ^ value); - trace_add_input_randomness(POOL_ENTROPY_BITS()); + trace_add_input_randomness(input_pool.entropy_count); } EXPORT_SYMBOL_GPL(add_input_randomness); @@ -1112,7 +1056,7 @@ void add_disk_randomness(struct gendisk *disk) return; /* first major is 1, so we get >= 0x200 here */ add_timer_randomness(disk->random, 0x100 + disk_devt(disk)); - trace_add_disk_randomness(disk_devt(disk), POOL_ENTROPY_BITS()); + trace_add_disk_randomness(disk_devt(disk), input_pool.entropy_count); } EXPORT_SYMBOL_GPL(add_disk_randomness); #endif @@ -1137,7 +1081,7 @@ static void extract_entropy(void *buf, size_t nbytes) } block; size_t i; - trace_extract_entropy(nbytes, POOL_ENTROPY_BITS()); + trace_extract_entropy(nbytes, input_pool.entropy_count); for (i = 0; i < ARRAY_SIZE(block.rdrand); ++i) { if (!arch_get_random_long(&block.rdrand[i])) @@ -1486,9 +1430,9 @@ static ssize_t urandom_read_nowarn(struct file *file, char __user *buf, { int ret; - nbytes = min_t(size_t, nbytes, INT_MAX >> (POOL_ENTROPY_SHIFT + 3)); + nbytes = min_t(size_t, nbytes, INT_MAX >> 6); ret = extract_crng_user(buf, nbytes); - trace_urandom_read(8 * nbytes, 0, POOL_ENTROPY_BITS()); + trace_urandom_read(8 * nbytes, 0, input_pool.entropy_count); return ret; } @@ -1527,7 +1471,7 @@ static __poll_t random_poll(struct file *file, poll_table *wait) mask = 0; if (crng_ready()) mask |= EPOLLIN | EPOLLRDNORM; - if (POOL_ENTROPY_BITS() < random_write_wakeup_bits) + if (input_pool.entropy_count < random_write_wakeup_bits) mask |= EPOLLOUT | EPOLLWRNORM; return mask; } @@ -1582,8 +1526,7 @@ static long random_ioctl(struct file *f, unsigned int cmd, unsigned long arg) switch (cmd) { case RNDGETENTCNT: /* inherently racy, no point locking */ - ent_count = POOL_ENTROPY_BITS(); - if (put_user(ent_count, p)) + if (put_user(input_pool.entropy_count, p)) return -EFAULT; return 0; case RNDADDTOENTCNT: @@ -1734,23 +1677,6 @@ static int proc_do_uuid(struct ctl_table *table, int write, void *buffer, return proc_dostring(&fake_table, write, buffer, lenp, ppos); } -/* - * Return entropy available scaled to integral bits - */ -static int proc_do_entropy(struct ctl_table *table, int write, void *buffer, - size_t *lenp, loff_t *ppos) -{ - struct ctl_table fake_table; - int entropy_count; - - entropy_count = *(int *)table->data >> POOL_ENTROPY_SHIFT; - - fake_table.data = &entropy_count; - fake_table.maxlen = sizeof(entropy_count); - - return proc_dointvec(&fake_table, write, buffer, lenp, ppos); -} - static int sysctl_poolsize = POOL_BITS; static struct ctl_table random_table[] = { { @@ -1762,10 +1688,10 @@ static struct ctl_table random_table[] = { }, { .procname = "entropy_avail", + .data = &input_pool.entropy_count, .maxlen = sizeof(int), .mode = 0444, - .proc_handler = proc_do_entropy, - .data = &input_pool.entropy_count, + .proc_handler = proc_dointvec, }, { .procname = "write_wakeup_threshold", @@ -1972,7 +1898,7 @@ void add_hwgenerator_randomness(const char *buffer, size_t count, */ wait_event_interruptible_timeout(random_write_wait, !system_wq || kthread_should_stop() || - POOL_ENTROPY_BITS() <= random_write_wakeup_bits, + input_pool.entropy_count <= random_write_wakeup_bits, CRNG_RESEED_INTERVAL); mix_pool_bytes(buffer, count); credit_entropy_bits(entropy); |