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FETCH(9) FreeBSD Kernel Developer's Manual FETCH(9) NAME fetch, fubyte, fuword, fuword16, fuword32, fuword64, fueword, fueword32, fueword64 - fetch data from user-space SYNOPSIS #include <sys/types.h> #include <sys/systm.h> int fubyte(volatile const void *base); long fuword(volatile const void *base); int fuword16(volatile const void *base); int32_t fuword32(volatile const void *base); int64_t fuword64(volatile const void *base); int fueword(volatile const void *base, long *val); int fueword32(volatile const void *base, int32_t *val); int fueword64(volatile const void *base, int64_t *val); DESCRIPTION The fetch functions are designed to copy small amounts of data from user- space of the current process. If the user address is naturally aligned, then the operation will be performed atomically. Otherwise it may fail or be performed non-atomically, depending on the platform. The fetch routines provide the following functionality: fubyte() Fetches a byte of data from the user-space address base. The byte read is zero-extended into the results variable. fuword() Fetches a word of data (long) from the user-space address base. fuword16() Fetches 16 bits of data from the user-space address base. The half-word read is zero-extended into the results variable. fuword32() Fetches 32 bits of data from the user-space address base. fuword64() Fetches 64 bits of data from the user-space address base. fueword() Fetches a word of data (long) from the user-space address base and stores the result in the variable pointed by val. fueword32() Fetches 32 bits of data from the user-space address base and stores the result in the variable pointed by val. fueword64() Fetches 64 bits of data from the user-space address base and stores the result in the variable pointed by val. The callers of fuword(), fuword32() and fuword64() functions cannot distinguish between -1 read from userspace and function failure. RETURN VALUES The fubyte(), fuword(), fuword16(), fuword32(), and fuword64() functions return the data fetched or -1 on failure. The fueword(), fueword32() and fueword64() functions return 0 on success and -1 on failure. SEE ALSO copy(9), store(9) FreeBSD 14.1-RELEASE-p8 July 22, 2021 FreeBSD 14.1-RELEASE-p8