Fix minor mistakes

Documentation/chap-device-drivers.tex

@@ -90,7 +90,7 @@ A call to this generic function returns an instance of the class
 
 \Defgeneric {read-block} {disk block address}
 
-Write a block of data to the disk.  The parameter \textit{disk} is an
+Read a block of data from the disk.  The parameter \textit{disk} is an
 instance of the class \textit{disk}, and \textit{block} is a a vector
 of type \texttt{(simple-array (unsigned-byte 8) (*))}.  The size of
 \textit{block} must be a power of 2, and the address must be aligned

Documentation/chap-protection.tex

@@ -70,7 +70,7 @@ execution is switched to \emph{user mode}.  As with traditional modern
 operating systems, the code of such software has its own \emph{address
   space}, which means that it can not directly manipulate \sysname{}
 capabilities.  Instead, it has to communicate with the system through
-the user of \emph{system calls}.  A system-wide object is referred to
+the use of \emph{system calls}.  A system-wide object is referred to
 by such code through an interposing \emph{object descriptor}, much
 like a file descriptor in \unix{}.  The details of this mechanism have
 not yet been fully determined.