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/*
* include/linux/random.h
*
* Include file for the random number generator.
*/
#ifndef _LINUX_RANDOM_H
#define _LINUX_RANDOM_H
#include <unistd.h>
#include <sys/syscall.h>
#include <linux/bug.h>
#include <linux/log2.h>
#ifdef SYS_getrandom
static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
{
return syscall(SYS_getrandom, buf, buflen, flags);
}
#else
extern int urandom_fd;
static inline int getrandom(void *buf, size_t buflen, unsigned int flags)
{
return read(urandom_fd, buf, buflen);
}
#endif
static inline void get_random_bytes(void *buf, int nbytes)
{
BUG_ON(getrandom(buf, nbytes, 0) != nbytes);
}
#define get_random_type(type) \
static inline type get_random_##type(void) \
{ \
type v; \
\
get_random_bytes(&v, sizeof(v)); \
return v; \
}
get_random_type(int);
get_random_type(long);
get_random_type(u8);
get_random_type(u16);
get_random_type(u32);
get_random_type(u64);
static inline u32 get_random_u32_below(u32 ceil)
{
if (ceil <= 1)
return 0;
for (;;) {
if (ceil <= 1U << 8) {
u32 mult = ceil * get_random_u8();
if (likely(is_power_of_2(ceil) || (u8)mult >= (1U << 8) % ceil))
return mult >> 8;
} else if (ceil <= 1U << 16) {
u32 mult = ceil * get_random_u16();
if (likely(is_power_of_2(ceil) || (u16)mult >= (1U << 16) % ceil))
return mult >> 16;
} else {
u64 mult = (u64)ceil * get_random_u32();
if (likely(is_power_of_2(ceil) || (u32)mult >= -ceil % ceil))
return mult >> 32;
}
}
}
#endif /* _LINUX_RANDOM_H */
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