Retrieves a byte of data from user memory.
#include <sys/types.h> #include <sys/errno.h> int fubyte ( uaddr) uchar *uaddr;
Item | Description |
---|---|
uaddr | Specifies the address of the user data. |
The fubyte kernel service fetches, or retrieves, a byte of data from the specified address in user memory. It is provided so that system calls and device heads can safely access user data. The fubyte service ensures that the user has the appropriate authority to:
The fubyte service should be called only while executing in kernel mode in the user process.
The fubyte kernel service can be called from the process environment only.
When successful, the fubyte service returns the specified byte.
Item | Description |
---|---|
-1 | Indicates a uaddr parameter that is not valid. |
The access is not valid under the following circumstances: