NAME
fetch, fubyte, fuword, fuword16, fuword32, fuword64, fueptr, 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
fueptr(volatile const void *base, intptr_t *val);
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.
- fueptr()
-
Fetches a pointer from the user-space address base and stores the result in the variable pointed by val. fueptr() preserves the provenance of pointers fetched from user-space (see memory_model(7) for further information).
- 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 fueptr(), fueword(), fueword32() and fueword64() functions return 0 on success and -1 on failure.