From: "Jason A. Donenfeld" Jason@zx2c4.com
commit 3655adc7089da4f8ca74cec8fcef73ea5101430e upstream.
This pulls all of the crng-focused functions into the second labeled section.
No functional changes.
Cc: Theodore Ts'o tytso@mit.edu Reviewed-by: Dominik Brodowski linux@dominikbrodowski.net Reviewed-by: Eric Biggers ebiggers@google.com Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/char/random.c | 786 +++++++++++++++++++++++++------------------------- 1 file changed, 407 insertions(+), 379 deletions(-)
--- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -380,122 +380,27 @@ static void _warn_unseeded_randomness(co }
-enum { - POOL_BITS = BLAKE2S_HASH_SIZE * 8, - POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */ -}; - -/* - * Static global variables - */ -static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); - -static int crng_init_cnt = 0; - -/********************************************************************** +/********************************************************************* * - * OS independent entropy store. Here are the functions which handle - * storing entropy in an entropy pool. + * Fast key erasure RNG, the "crng". * - **********************************************************************/ - -static struct { - struct blake2s_state hash; - spinlock_t lock; - unsigned int entropy_count; -} input_pool = { - .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), - BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, - BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, - .hash.outlen = BLAKE2S_HASH_SIZE, - .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), -}; - -static void extract_entropy(void *buf, size_t nbytes); -static bool drain_entropy(void *buf, size_t nbytes); - -static void crng_reseed(void); - -/* - * This function adds bytes into the entropy "pool". It does not - * update the entropy estimate. The caller should call - * credit_entropy_bits if this is appropriate. - */ -static void _mix_pool_bytes(const void *in, size_t nbytes) -{ - blake2s_update(&input_pool.hash, in, nbytes); -} - -static void mix_pool_bytes(const void *in, size_t nbytes) -{ - unsigned long flags; - - spin_lock_irqsave(&input_pool.lock, flags); - _mix_pool_bytes(in, nbytes); - spin_unlock_irqrestore(&input_pool.lock, flags); -} - -struct fast_pool { - union { - u32 pool32[4]; - u64 pool64[2]; - }; - unsigned long last; - u16 reg_idx; - u8 count; -}; - -/* - * This is a fast mixing routine used by the interrupt randomness - * collector. It's hardcoded for an 128 bit pool and assumes that any - * locks that might be needed are taken by the caller. - */ -static void fast_mix(u32 pool[4]) -{ - u32 a = pool[0], b = pool[1]; - u32 c = pool[2], d = pool[3]; - - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; - - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; - - a += b; c += d; - b = rol32(b, 6); d = rol32(d, 27); - d ^= a; b ^= c; - - a += b; c += d; - b = rol32(b, 16); d = rol32(d, 14); - d ^= a; b ^= c; - - pool[0] = a; pool[1] = b; - pool[2] = c; pool[3] = d; -} - -static void credit_entropy_bits(size_t nbits) -{ - unsigned int entropy_count, orig, add; - - if (!nbits) - return; - - add = min_t(size_t, nbits, POOL_BITS); - - do { - orig = READ_ONCE(input_pool.entropy_count); - entropy_count = min_t(unsigned int, POOL_BITS, orig + add); - } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); - - if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) - crng_reseed(); -} - -/********************************************************************* + * These functions expand entropy from the entropy extractor into + * long streams for external consumption using the "fast key erasure" + * RNG described at https://blog.cr.yp.to/20170723-random.html. * - * CRNG using CHACHA20 + * There are a few exported interfaces for use by other drivers: + * + * void get_random_bytes(void *buf, size_t nbytes) + * u32 get_random_u32() + * u64 get_random_u64() + * unsigned int get_random_int() + * unsigned long get_random_long() + * + * These interfaces will return the requested number of random bytes + * into the given buffer or as a return value. This is equivalent to + * a read from /dev/urandom. The integer family of functions may be + * higher performance for one-off random integers, because they do a + * bit of buffering. * *********************************************************************/
@@ -522,70 +427,14 @@ static DEFINE_PER_CPU(struct crng, crngs .generation = ULONG_MAX };
-/* - * crng_fast_load() can be called by code in the interrupt service - * path. So we can't afford to dilly-dally. Returns the number of - * bytes processed from cp. - */ -static size_t crng_fast_load(const void *cp, size_t len) -{ - unsigned long flags; - const u8 *src = (const u8 *)cp; - size_t ret = 0; - - if (!spin_trylock_irqsave(&base_crng.lock, flags)) - return 0; - if (crng_init != 0) { - spin_unlock_irqrestore(&base_crng.lock, flags); - return 0; - } - while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { - base_crng.key[crng_init_cnt % sizeof(base_crng.key)] ^= *src; - src++; crng_init_cnt++; len--; ret++; - } - if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { - ++base_crng.generation; - crng_init = 1; - } - spin_unlock_irqrestore(&base_crng.lock, flags); - if (crng_init == 1) - pr_notice("fast init done\n"); - return ret; -} +/* Used by crng_reseed() to extract a new seed from the input pool. */ +static bool drain_entropy(void *buf, size_t nbytes);
/* - * crng_slow_load() is called by add_device_randomness, which has two - * attributes. (1) We can't trust the buffer passed to it is - * guaranteed to be unpredictable (so it might not have any entropy at - * all), and (2) it doesn't have the performance constraints of - * crng_fast_load(). - * - * So, we simply hash the contents in with the current key. Finally, - * we do *not* advance crng_init_cnt since buffer we may get may be - * something like a fixed DMI table (for example), which might very - * well be unique to the machine, but is otherwise unvarying. + * This extracts a new crng key from the input pool, but only if there is a + * sufficient amount of entropy available, in order to mitigate bruteforcing + * of newly added bits. */ -static void crng_slow_load(const void *cp, size_t len) -{ - unsigned long flags; - struct blake2s_state hash; - - blake2s_init(&hash, sizeof(base_crng.key)); - - if (!spin_trylock_irqsave(&base_crng.lock, flags)) - return; - if (crng_init != 0) { - spin_unlock_irqrestore(&base_crng.lock, flags); - return; - } - - blake2s_update(&hash, base_crng.key, sizeof(base_crng.key)); - blake2s_update(&hash, cp, len); - blake2s_final(&hash, base_crng.key); - - spin_unlock_irqrestore(&base_crng.lock, flags); -} - static void crng_reseed(void) { unsigned long flags; @@ -635,13 +484,11 @@ static void crng_reseed(void) }
/* - * The general form here is based on a "fast key erasure RNG" from - * https://blog.cr.yp.to/20170723-random.html. It generates a ChaCha - * block using the provided key, and then immediately overwites that - * key with half the block. It returns the resultant ChaCha state to the - * user, along with the second half of the block containing 32 bytes of - * random data that may be used; random_data_len may not be greater than - * 32. + * This generates a ChaCha block using the provided key, and then + * immediately overwites that key with half the block. It returns + * the resultant ChaCha state to the user, along with the second + * half of the block containing 32 bytes of random data that may + * be used; random_data_len may not be greater than 32. */ static void crng_fast_key_erasure(u8 key[CHACHA_KEY_SIZE], u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)], @@ -728,6 +575,126 @@ static void crng_make_state(u32 chacha_s local_irq_restore(flags); }
+/* + * This function is for crng_init == 0 only. + * + * crng_fast_load() can be called by code in the interrupt service + * path. So we can't afford to dilly-dally. Returns the number of + * bytes processed from cp. + */ +static size_t crng_fast_load(const void *cp, size_t len) +{ + static int crng_init_cnt = 0; + unsigned long flags; + const u8 *src = (const u8 *)cp; + size_t ret = 0; + + if (!spin_trylock_irqsave(&base_crng.lock, flags)) + return 0; + if (crng_init != 0) { + spin_unlock_irqrestore(&base_crng.lock, flags); + return 0; + } + while (len > 0 && crng_init_cnt < CRNG_INIT_CNT_THRESH) { + base_crng.key[crng_init_cnt % sizeof(base_crng.key)] ^= *src; + src++; crng_init_cnt++; len--; ret++; + } + if (crng_init_cnt >= CRNG_INIT_CNT_THRESH) { + ++base_crng.generation; + crng_init = 1; + } + spin_unlock_irqrestore(&base_crng.lock, flags); + if (crng_init == 1) + pr_notice("fast init done\n"); + return ret; +} + +/* + * This function is for crng_init == 0 only. + * + * crng_slow_load() is called by add_device_randomness, which has two + * attributes. (1) We can't trust the buffer passed to it is + * guaranteed to be unpredictable (so it might not have any entropy at + * all), and (2) it doesn't have the performance constraints of + * crng_fast_load(). + * + * So, we simply hash the contents in with the current key. Finally, + * we do *not* advance crng_init_cnt since buffer we may get may be + * something like a fixed DMI table (for example), which might very + * well be unique to the machine, but is otherwise unvarying. + */ +static void crng_slow_load(const void *cp, size_t len) +{ + unsigned long flags; + struct blake2s_state hash; + + blake2s_init(&hash, sizeof(base_crng.key)); + + if (!spin_trylock_irqsave(&base_crng.lock, flags)) + return; + if (crng_init != 0) { + spin_unlock_irqrestore(&base_crng.lock, flags); + return; + } + + blake2s_update(&hash, base_crng.key, sizeof(base_crng.key)); + blake2s_update(&hash, cp, len); + blake2s_final(&hash, base_crng.key); + + spin_unlock_irqrestore(&base_crng.lock, flags); +} + +static void _get_random_bytes(void *buf, size_t nbytes) +{ + u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)]; + u8 tmp[CHACHA_BLOCK_SIZE]; + size_t len; + + if (!nbytes) + return; + + len = min_t(size_t, 32, nbytes); + crng_make_state(chacha_state, buf, len); + nbytes -= len; + buf += len; + + while (nbytes) { + if (nbytes < CHACHA_BLOCK_SIZE) { + chacha20_block(chacha_state, tmp); + memcpy(buf, tmp, nbytes); + memzero_explicit(tmp, sizeof(tmp)); + break; + } + + chacha20_block(chacha_state, buf); + if (unlikely(chacha_state[12] == 0)) + ++chacha_state[13]; + nbytes -= CHACHA_BLOCK_SIZE; + buf += CHACHA_BLOCK_SIZE; + } + + memzero_explicit(chacha_state, sizeof(chacha_state)); +} + +/* + * This function is the exported kernel interface. It returns some + * number of good random numbers, suitable for key generation, seeding + * TCP sequence numbers, etc. It does not rely on the hardware random + * number generator. For random bytes direct from the hardware RNG + * (when available), use get_random_bytes_arch(). In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. + */ +void get_random_bytes(void *buf, size_t nbytes) +{ + static void *previous; + + warn_unseeded_randomness(&previous); + _get_random_bytes(buf, nbytes); +} +EXPORT_SYMBOL(get_random_bytes); + static ssize_t get_random_bytes_user(void __user *buf, size_t nbytes) { bool large_request = nbytes > 256; @@ -775,6 +742,265 @@ static ssize_t get_random_bytes_user(voi return ret; }
+/* + * Batched entropy returns random integers. The quality of the random + * number is good as /dev/urandom. In order to ensure that the randomness + * provided by this function is okay, the function wait_for_random_bytes() + * should be called and return 0 at least once at any point prior. + */ +struct batched_entropy { + union { + /* + * We make this 1.5x a ChaCha block, so that we get the + * remaining 32 bytes from fast key erasure, plus one full + * block from the detached ChaCha state. We can increase + * the size of this later if needed so long as we keep the + * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. + */ + u64 entropy_u64[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u64))]; + u32 entropy_u32[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u32))]; + }; + unsigned long generation; + unsigned int position; +}; + + +static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = { + .position = UINT_MAX +}; + +u64 get_random_u64(void) +{ + u64 ret; + unsigned long flags; + struct batched_entropy *batch; + static void *previous; + unsigned long next_gen; + + warn_unseeded_randomness(&previous); + + local_irq_save(flags); + batch = raw_cpu_ptr(&batched_entropy_u64); + + next_gen = READ_ONCE(base_crng.generation); + if (batch->position >= ARRAY_SIZE(batch->entropy_u64) || + next_gen != batch->generation) { + _get_random_bytes(batch->entropy_u64, sizeof(batch->entropy_u64)); + batch->position = 0; + batch->generation = next_gen; + } + + ret = batch->entropy_u64[batch->position]; + batch->entropy_u64[batch->position] = 0; + ++batch->position; + local_irq_restore(flags); + return ret; +} +EXPORT_SYMBOL(get_random_u64); + +static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = { + .position = UINT_MAX +}; + +u32 get_random_u32(void) +{ + u32 ret; + unsigned long flags; + struct batched_entropy *batch; + static void *previous; + unsigned long next_gen; + + warn_unseeded_randomness(&previous); + + local_irq_save(flags); + batch = raw_cpu_ptr(&batched_entropy_u32); + + next_gen = READ_ONCE(base_crng.generation); + if (batch->position >= ARRAY_SIZE(batch->entropy_u32) || + next_gen != batch->generation) { + _get_random_bytes(batch->entropy_u32, sizeof(batch->entropy_u32)); + batch->position = 0; + batch->generation = next_gen; + } + + ret = batch->entropy_u32[batch->position]; + batch->entropy_u32[batch->position] = 0; + ++batch->position; + local_irq_restore(flags); + return ret; +} +EXPORT_SYMBOL(get_random_u32); + +/** + * randomize_page - Generate a random, page aligned address + * @start: The smallest acceptable address the caller will take. + * @range: The size of the area, starting at @start, within which the + * random address must fall. + * + * If @start + @range would overflow, @range is capped. + * + * NOTE: Historical use of randomize_range, which this replaces, presumed that + * @start was already page aligned. We now align it regardless. + * + * Return: A page aligned address within [start, start + range). On error, + * @start is returned. + */ +unsigned long randomize_page(unsigned long start, unsigned long range) +{ + if (!PAGE_ALIGNED(start)) { + range -= PAGE_ALIGN(start) - start; + start = PAGE_ALIGN(start); + } + + if (start > ULONG_MAX - range) + range = ULONG_MAX - start; + + range >>= PAGE_SHIFT; + + if (range == 0) + return start; + + return start + (get_random_long() % range << PAGE_SHIFT); +} + +/* + * This function will use the architecture-specific hardware random + * number generator if it is available. It is not recommended for + * use. Use get_random_bytes() instead. It returns the number of + * bytes filled in. + */ +size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes) +{ + size_t left = nbytes; + u8 *p = buf; + + while (left) { + unsigned long v; + size_t chunk = min_t(size_t, left, sizeof(unsigned long)); + + if (!arch_get_random_long(&v)) + break; + + memcpy(p, &v, chunk); + p += chunk; + left -= chunk; + } + + return nbytes - left; +} +EXPORT_SYMBOL(get_random_bytes_arch); + +enum { + POOL_BITS = BLAKE2S_HASH_SIZE * 8, + POOL_MIN_BITS = POOL_BITS /* No point in settling for less. */ +}; + +/* + * Static global variables + */ +static DECLARE_WAIT_QUEUE_HEAD(random_write_wait); + +/********************************************************************** + * + * OS independent entropy store. Here are the functions which handle + * storing entropy in an entropy pool. + * + **********************************************************************/ + +static struct { + struct blake2s_state hash; + spinlock_t lock; + unsigned int entropy_count; +} input_pool = { + .hash.h = { BLAKE2S_IV0 ^ (0x01010000 | BLAKE2S_HASH_SIZE), + BLAKE2S_IV1, BLAKE2S_IV2, BLAKE2S_IV3, BLAKE2S_IV4, + BLAKE2S_IV5, BLAKE2S_IV6, BLAKE2S_IV7 }, + .hash.outlen = BLAKE2S_HASH_SIZE, + .lock = __SPIN_LOCK_UNLOCKED(input_pool.lock), +}; + +static void extract_entropy(void *buf, size_t nbytes); +static bool drain_entropy(void *buf, size_t nbytes); + +static void crng_reseed(void); + +/* + * This function adds bytes into the entropy "pool". It does not + * update the entropy estimate. The caller should call + * credit_entropy_bits if this is appropriate. + */ +static void _mix_pool_bytes(const void *in, size_t nbytes) +{ + blake2s_update(&input_pool.hash, in, nbytes); +} + +static void mix_pool_bytes(const void *in, size_t nbytes) +{ + unsigned long flags; + + spin_lock_irqsave(&input_pool.lock, flags); + _mix_pool_bytes(in, nbytes); + spin_unlock_irqrestore(&input_pool.lock, flags); +} + +struct fast_pool { + union { + u32 pool32[4]; + u64 pool64[2]; + }; + unsigned long last; + u16 reg_idx; + u8 count; +}; + +/* + * This is a fast mixing routine used by the interrupt randomness + * collector. It's hardcoded for an 128 bit pool and assumes that any + * locks that might be needed are taken by the caller. + */ +static void fast_mix(u32 pool[4]) +{ + u32 a = pool[0], b = pool[1]; + u32 c = pool[2], d = pool[3]; + + a += b; c += d; + b = rol32(b, 6); d = rol32(d, 27); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 16); d = rol32(d, 14); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 6); d = rol32(d, 27); + d ^= a; b ^= c; + + a += b; c += d; + b = rol32(b, 16); d = rol32(d, 14); + d ^= a; b ^= c; + + pool[0] = a; pool[1] = b; + pool[2] = c; pool[3] = d; +} + +static void credit_entropy_bits(size_t nbits) +{ + unsigned int entropy_count, orig, add; + + if (!nbits) + return; + + add = min_t(size_t, nbits, POOL_BITS); + + do { + orig = READ_ONCE(input_pool.entropy_count); + entropy_count = min_t(unsigned int, POOL_BITS, orig + add); + } while (cmpxchg(&input_pool.entropy_count, orig, entropy_count) != orig); + + if (crng_init < 2 && entropy_count >= POOL_MIN_BITS) + crng_reseed(); +} + /********************************************************************* * * Entropy input management @@ -1043,57 +1269,6 @@ static bool drain_entropy(void *buf, siz }
/* - * This function is the exported kernel interface. It returns some - * number of good random numbers, suitable for key generation, seeding - * TCP sequence numbers, etc. It does not rely on the hardware random - * number generator. For random bytes direct from the hardware RNG - * (when available), use get_random_bytes_arch(). In order to ensure - * that the randomness provided by this function is okay, the function - * wait_for_random_bytes() should be called and return 0 at least once - * at any point prior. - */ -static void _get_random_bytes(void *buf, size_t nbytes) -{ - u32 chacha_state[CHACHA_BLOCK_SIZE / sizeof(u32)]; - u8 tmp[CHACHA_BLOCK_SIZE]; - size_t len; - - if (!nbytes) - return; - - len = min_t(size_t, 32, nbytes); - crng_make_state(chacha_state, buf, len); - nbytes -= len; - buf += len; - - while (nbytes) { - if (nbytes < CHACHA_BLOCK_SIZE) { - chacha20_block(chacha_state, tmp); - memcpy(buf, tmp, nbytes); - memzero_explicit(tmp, sizeof(tmp)); - break; - } - - chacha20_block(chacha_state, buf); - if (unlikely(chacha_state[12] == 0)) - ++chacha_state[13]; - nbytes -= CHACHA_BLOCK_SIZE; - buf += CHACHA_BLOCK_SIZE; - } - - memzero_explicit(chacha_state, sizeof(chacha_state)); -} - -void get_random_bytes(void *buf, size_t nbytes) -{ - static void *previous; - - warn_unseeded_randomness(&previous); - _get_random_bytes(buf, nbytes); -} -EXPORT_SYMBOL(get_random_bytes); - -/* * Each time the timer fires, we expect that we got an unpredictable * jump in the cycle counter. Even if the timer is running on another * CPU, the timer activity will be touching the stack of the CPU that is @@ -1142,33 +1317,6 @@ static void try_to_generate_entropy(void mix_pool_bytes(&stack.now, sizeof(stack.now)); }
-/* - * This function will use the architecture-specific hardware random - * number generator if it is available. It is not recommended for - * use. Use get_random_bytes() instead. It returns the number of - * bytes filled in. - */ -size_t __must_check get_random_bytes_arch(void *buf, size_t nbytes) -{ - size_t left = nbytes; - u8 *p = buf; - - while (left) { - unsigned long v; - size_t chunk = min_t(size_t, left, sizeof(unsigned long)); - - if (!arch_get_random_long(&v)) - break; - - memcpy(p, &v, chunk); - p += chunk; - left -= chunk; - } - - return nbytes - left; -} -EXPORT_SYMBOL(get_random_bytes_arch); - static bool trust_cpu __ro_after_init = IS_ENABLED(CONFIG_RANDOM_TRUST_CPU); static int __init parse_trust_cpu(char *arg) { @@ -1521,126 +1669,6 @@ struct ctl_table random_table[] = { }; #endif /* CONFIG_SYSCTL */
-struct batched_entropy { - union { - /* - * We make this 1.5x a ChaCha block, so that we get the - * remaining 32 bytes from fast key erasure, plus one full - * block from the detached ChaCha state. We can increase - * the size of this later if needed so long as we keep the - * formula of (integer_blocks + 0.5) * CHACHA_BLOCK_SIZE. - */ - u64 entropy_u64[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u64))]; - u32 entropy_u32[CHACHA_BLOCK_SIZE * 3 / (2 * sizeof(u32))]; - }; - unsigned long generation; - unsigned int position; -}; - -/* - * Get a random word for internal kernel use only. The quality of the random - * number is good as /dev/urandom. In order to ensure that the randomness - * provided by this function is okay, the function wait_for_random_bytes() - * should be called and return 0 at least once at any point prior. - */ -static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64) = { - .position = UINT_MAX -}; - -u64 get_random_u64(void) -{ - u64 ret; - unsigned long flags; - struct batched_entropy *batch; - static void *previous; - unsigned long next_gen; - - warn_unseeded_randomness(&previous); - - local_irq_save(flags); - batch = raw_cpu_ptr(&batched_entropy_u64); - - next_gen = READ_ONCE(base_crng.generation); - if (batch->position >= ARRAY_SIZE(batch->entropy_u64) || - next_gen != batch->generation) { - _get_random_bytes(batch->entropy_u64, sizeof(batch->entropy_u64)); - batch->position = 0; - batch->generation = next_gen; - } - - ret = batch->entropy_u64[batch->position]; - batch->entropy_u64[batch->position] = 0; - ++batch->position; - local_irq_restore(flags); - return ret; -} -EXPORT_SYMBOL(get_random_u64); - -static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u32) = { - .position = UINT_MAX -}; - -u32 get_random_u32(void) -{ - u32 ret; - unsigned long flags; - struct batched_entropy *batch; - static void *previous; - unsigned long next_gen; - - warn_unseeded_randomness(&previous); - - local_irq_save(flags); - batch = raw_cpu_ptr(&batched_entropy_u32); - - next_gen = READ_ONCE(base_crng.generation); - if (batch->position >= ARRAY_SIZE(batch->entropy_u32) || - next_gen != batch->generation) { - _get_random_bytes(batch->entropy_u32, sizeof(batch->entropy_u32)); - batch->position = 0; - batch->generation = next_gen; - } - - ret = batch->entropy_u32[batch->position]; - batch->entropy_u32[batch->position] = 0; - ++batch->position; - local_irq_restore(flags); - return ret; -} -EXPORT_SYMBOL(get_random_u32); - -/** - * randomize_page - Generate a random, page aligned address - * @start: The smallest acceptable address the caller will take. - * @range: The size of the area, starting at @start, within which the - * random address must fall. - * - * If @start + @range would overflow, @range is capped. - * - * NOTE: Historical use of randomize_range, which this replaces, presumed that - * @start was already page aligned. We now align it regardless. - * - * Return: A page aligned address within [start, start + range). On error, - * @start is returned. - */ -unsigned long randomize_page(unsigned long start, unsigned long range) -{ - if (!PAGE_ALIGNED(start)) { - range -= PAGE_ALIGN(start) - start; - start = PAGE_ALIGN(start); - } - - if (start > ULONG_MAX - range) - range = ULONG_MAX - start; - - range >>= PAGE_SHIFT; - - if (range == 0) - return start; - - return start + (get_random_long() % range << PAGE_SHIFT); -} - /* Interface for in-kernel drivers of true hardware RNGs. * Those devices may produce endless random bits and will be throttled * when our pool is full.