include/linux/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
  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
  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
  35 static inline int register_random_vmfork_notifier(struct notifier_block *nb) { return 0; }
  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);
  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  */
  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  */
  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  */
 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. */
 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 #ifdef CONFIG_SMP
 149 int random_prepare_cpu(unsigned int cpu);
 150 int random_online_cpu(unsigned int cpu);
 151 #endif
 152
 153 #ifndef MODULE
 154 extern const struct file_operations random_fops, urandom_fops;
 155 #endif
 156
 157 #endif /* _LINUX_RANDOM_H */