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.TH MPROTECT 2 "Jan 12, 1998"
.SH NAME
mprotect \- set protection of memory mapping
.SH SYNOPSIS
.LP
.nf
#include <sys/mman.h>

\fBint\fR \fBmprotect\fR(\fBvoid *\fR\fIaddr\fR, \fBsize_t\fR \fIlen\fR, \fBint\fR \fIprot\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The  \fBmprotect()\fR function changes the access protections on the mappings
specified by the range [\fIaddr, addr + len\fR\|), rounding \fIlen\fR up to the
next multiple of the page size as returned by \fBsysconf\fR(3C), to be that
specified by \fIprot\fR. Legitimate values for \fIprot\fR are the same as those
permitted for \fBmmap\fR(2) and are defined in <\fBsys/mman.h\fR> as:
.sp
.ne 2
.na
\fB\fBPROT_READ\fR\fR
.ad
.RS 14n
\fB/* page can be read */\fR
.RE

.sp
.ne 2
.na
\fB\fBPROT_WRITE\fR\fR
.ad
.RS 14n
\fB/* page can be written */\fR
.RE

.sp
.ne 2
.na
\fB\fBPROT_EXEC\fR\fR
.ad
.RS 14n
\fB/* page can be executed */\fR
.RE

.sp
.ne 2
.na
\fB\fBPROT_NONE\fR\fR
.ad
.RS 14n
\fB/* page can not be accessed */\fR
.RE

.sp
.LP
When \fBmprotect()\fR fails for reasons other than \fBEINVAL\fR, the
protections on some of the pages in the range [\fIaddr, addr + len\fR) may have
been changed. If the error occurs on some page at \fIaddr2\fR, then the
protections of all whole pages in the range [\fIaddr, addr2\fR] will have been
modified.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBmprotect()\fR returns \fB0\fR. Otherwise, it
returns \fB\(mi1\fR and sets \fBerrno\fR to indicate the error.
.SH ERRORS
.sp
.LP
The \fBmprotect()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEACCES\fR\fR
.ad
.RS 10n
The \fIprot\fR argument specifies a protection that violates the access
permission the process has to the underlying memory object.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIlen\fR argument has a value equal to 0, or \fIaddr\fR is not a multiple
of the page size as returned by \fBsysconf\fR(3C).
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Addresses in the range [\fIaddr, addr + len\fR) are invalid for the address
space of a process, or specify one or more pages which are not mapped.
.RE

.sp
.LP
The \fBmprotect()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
The address range [\fIaddr, addr + len\fR) includes one or more pages that have
been locked in memory and that were mapped \fB\fR\fBMAP_PRIVATE\fR\fB;\fR
\fIprot\fR includes \fB\fR\fBPROT_WRITE\fR\fB;\fR and the system has
insufficient resources to reserve memory for the private pages that may be
created. These private pages may be created by store operations in the
now-writable address range.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
.TE

.SH SEE ALSO
.sp
.LP
.BR mmap (2),
.BR mlock (3C),
.BR mlockall (3C),
.BR plock (3C),
.BR sysconf (3C),
.BR attributes (7),
.BR standards (7)