random.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2
  3#ifndef _LINUX_RANDOM_H
  4#define _LINUX_RANDOM_H
  5
  6#include <linux/bug.h>
  7#include <linux/kernel.h>
  8#include <linux/list.h>
  9
 10#include <uapi/linux/random.h>
 11
 12struct notifier_block;
 13
 14void add_device_randomness(const void *buf, size_t len);
 15void __init add_bootloader_randomness(const void *buf, size_t len);
 16void add_input_randomness(unsigned int type, unsigned int code,
 17			  unsigned int value) __latent_entropy;
 18void add_interrupt_randomness(int irq) __latent_entropy;
 19void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after);
 20
 21static inline void add_latent_entropy(void)
 22{
 23#if defined(LATENT_ENTROPY_PLUGIN) && !defined(__CHECKER__)
 24	add_device_randomness((const void *)&latent_entropy, sizeof(latent_entropy));
 25#else
 26	add_device_randomness(NULL, 0);
 27#endif
 28}
 29
 30#if IS_ENABLED(CONFIG_VMGENID)
 31void add_vmfork_randomness(const void *unique_vm_id, size_t len);
 32int register_random_vmfork_notifier(struct notifier_block *nb);
 33int unregister_random_vmfork_notifier(struct notifier_block *nb);
 34#else
 35static inline int register_random_vmfork_notifier(struct notifier_block *nb) { return 0; }
 36static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { return 0; }
 37#endif
 38
 39void get_random_bytes(void *buf, size_t len);
 40u8 get_random_u8(void);
 41u16 get_random_u16(void);
 42u32 get_random_u32(void);
 43u64 get_random_u64(void);
 44static inline unsigned long get_random_long(void)
 45{
 46#if BITS_PER_LONG == 64
 47	return get_random_u64();
 48#else
 49	return get_random_u32();
 50#endif
 51}
 52
 53u32 __get_random_u32_below(u32 ceil);
 54
 55/*
 56 * Returns a random integer in the interval [0, ceil), with uniform
 57 * distribution, suitable for all uses. Fastest when ceil is a constant, but
 58 * still fast for variable ceil as well.
 59 */
 60static inline u32 get_random_u32_below(u32 ceil)
 61{
 62	if (!__builtin_constant_p(ceil))
 63		return __get_random_u32_below(ceil);
 64
 65	/*
 66	 * For the fast path, below, all operations on ceil are precomputed by
 67	 * the compiler, so this incurs no overhead for checking pow2, doing
 68	 * divisions, or branching based on integer size. The resultant
 69	 * algorithm does traditional reciprocal multiplication (typically
 70	 * optimized by the compiler into shifts and adds), rejecting samples
 71	 * whose lower half would indicate a range indivisible by ceil.
 72	 */
 73	BUILD_BUG_ON_MSG(!ceil, "get_random_u32_below() must take ceil > 0");
 74	if (ceil <= 1)
 75		return 0;
 76	for (;;) {
 77		if (ceil <= 1U << 8) {
 78			u32 mult = ceil * get_random_u8();
 79			if (likely(is_power_of_2(ceil) || (u8)mult >= (1U << 8) % ceil))
 80				return mult >> 8;
 81		} else if (ceil <= 1U << 16) {
 82			u32 mult = ceil * get_random_u16();
 83			if (likely(is_power_of_2(ceil) || (u16)mult >= (1U << 16) % ceil))
 84				return mult >> 16;
 85		} else {
 86			u64 mult = (u64)ceil * get_random_u32();
 87			if (likely(is_power_of_2(ceil) || (u32)mult >= -ceil % ceil))
 88				return mult >> 32;
 89		}
 90	}
 91}
 92
 93/*
 94 * Returns a random integer in the interval (floor, U32_MAX], with uniform
 95 * distribution, suitable for all uses. Fastest when floor is a constant, but
 96 * still fast for variable floor as well.
 97 */
 98static inline u32 get_random_u32_above(u32 floor)
 99{
100	BUILD_BUG_ON_MSG(__builtin_constant_p(floor) && floor == U32_MAX,
101			 "get_random_u32_above() must take floor < U32_MAX");
102	return floor + 1 + get_random_u32_below(U32_MAX - floor);
103}
104
105/*
106 * Returns a random integer in the interval [floor, ceil], with uniform
107 * distribution, suitable for all uses. Fastest when floor and ceil are
108 * constant, but still fast for variable floor and ceil as well.
109 */
110static inline u32 get_random_u32_inclusive(u32 floor, u32 ceil)
111{
112	BUILD_BUG_ON_MSG(__builtin_constant_p(floor) && __builtin_constant_p(ceil) &&
113			 (floor > ceil || ceil - floor == U32_MAX),
114			 "get_random_u32_inclusive() must take floor <= ceil");
115	return floor + get_random_u32_below(ceil - floor + 1);
116}
117
118void __init random_init_early(const char *command_line);
119void __init random_init(void);
120bool rng_is_initialized(void);
121int wait_for_random_bytes(void);
122int execute_with_initialized_rng(struct notifier_block *nb);
123
124/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes).
125 * Returns the result of the call to wait_for_random_bytes. */
126static inline int get_random_bytes_wait(void *buf, size_t nbytes)
127{
128	int ret = wait_for_random_bytes();
129	get_random_bytes(buf, nbytes);
130	return ret;
131}
132
133#ifdef CONFIG_SMP
134int random_prepare_cpu(unsigned int cpu);
135int random_online_cpu(unsigned int cpu);
136#endif
137
138#ifndef MODULE
139extern const struct file_operations random_fops, urandom_fops;
140#endif
141
142#endif /* _LINUX_RANDOM_H */