fetch(9) - NetBSD Manual Pages

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FETCH(9)                     NetBSD Kernel Manual                     FETCH(9)


NAME

     fetch, fubyte, fuibyte, fusword, fuswintr, fuword, fuiword - fetch data
     from user-space


SYNOPSIS

     #include <sys/types.h>
     #include <sys/systm.h>

     int
     fubyte(const void *base);

     int
     fusword(const void *base);

     int
     fuswintr(const void *base);

     long
     fuword(const void *base);


DESCRIPTION

     The fetch functions are designed to copy small amounts of data from user-
     space.

     The fetch routines provide the following functionality:

     fubyte()    Fetches a byte of data from the user-space address base.

     fusword()   Fetches a short word of data from the user-space address
                 base.

     fuswintr()  Fetches a short word of data from the user-space address
                 base.  This function is safe to call during an interrupt con-
                 text.

     fuword()    Fetches a word of data from the user-space address base.


RETURN VALUES

     The fetch functions return the data fetched or -1 on failure.  Note that
     these functions all do "unsigned" access, and therefore will never sign
     extend byte or short values.  This prevents ambiguity with the error re-
     turn value for all functions except fuword().


SEE ALSO

     copy(9), store(9)


BUGS

     The function fuword() has no way to unambiguously signal an error, be-
     cause the data it reads might legitimately be the same as the -1 used to
     indicate an error.  The other functions do not have this problem because
     the unsigned values returned by those can never match the -1 error return
     value.

NetBSD 1.6                      January 7, 1996                              1