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