xref: /openbmc/linux/include/linux/random.h (revision 6bb20c15)
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 
12 struct notifier_block;
13 
14 void add_device_randomness(const void *buf, size_t len);
15 void __init add_bootloader_randomness(const void *buf, size_t len);
16 void add_input_randomness(unsigned int type, unsigned int code,
17 			  unsigned int value) __latent_entropy;
18 void add_interrupt_randomness(int irq) __latent_entropy;
19 void add_hwgenerator_randomness(const void *buf, size_t len, size_t entropy, bool sleep_after);
20 
add_latent_entropy(void)21 static 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)
31 void add_vmfork_randomness(const void *unique_vm_id, size_t len);
32 int register_random_vmfork_notifier(struct notifier_block *nb);
33 int unregister_random_vmfork_notifier(struct notifier_block *nb);
34 #else
register_random_vmfork_notifier(struct notifier_block * nb)35 static inline int register_random_vmfork_notifier(struct notifier_block *nb) { return 0; }
unregister_random_vmfork_notifier(struct notifier_block * nb)36 static inline int unregister_random_vmfork_notifier(struct notifier_block *nb) { return 0; }
37 #endif
38 
39 void get_random_bytes(void *buf, size_t len);
40 u8 get_random_u8(void);
41 u16 get_random_u16(void);
42 u32 get_random_u32(void);
43 u64 get_random_u64(void);
get_random_long(void)44 static 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 
53 u32 __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  */
get_random_u32_below(u32 ceil)60 static 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  */
get_random_u32_above(u32 floor)98 static 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  */
get_random_u32_inclusive(u32 floor,u32 ceil)110 static 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 
118 void __init random_init_early(const char *command_line);
119 void __init random_init(void);
120 bool rng_is_initialized(void);
121 int wait_for_random_bytes(void);
122 int 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. */
get_random_bytes_wait(void * buf,size_t nbytes)126 static 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 #define declare_get_random_var_wait(name, ret_type) \
134 	static inline int get_random_ ## name ## _wait(ret_type *out) { \
135 		int ret = wait_for_random_bytes(); \
136 		if (unlikely(ret)) \
137 			return ret; \
138 		*out = get_random_ ## name(); \
139 		return 0; \
140 	}
141 declare_get_random_var_wait(u8, u8)
142 declare_get_random_var_wait(u16, u16)
143 declare_get_random_var_wait(u32, u32)
144 declare_get_random_var_wait(u64, u32)
145 declare_get_random_var_wait(long, unsigned long)
146 #undef declare_get_random_var
147 
148 /*
149  * This is designed to be standalone for just prandom
150  * users, but for now we include it from <linux/random.h>
151  * for legacy reasons.
152  */
153 #include <linux/prandom.h>
154 
155 #ifdef CONFIG_SMP
156 int random_prepare_cpu(unsigned int cpu);
157 int random_online_cpu(unsigned int cpu);
158 #endif
159 
160 #ifndef MODULE
161 extern const struct file_operations random_fops, urandom_fops;
162 #endif
163 
164 #endif /* _LINUX_RANDOM_H */
165