MPROTECT(3)                POSIX Programmer's Manual               MPROTECT(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       mprotect -- set protection of memory mapping

SYNOPSIS
       #include <sys/mman.h>

       int mprotect(void *addr, size_t len, int prot);

DESCRIPTION
       The mprotect() function shall change the access protections to be that
       specified by prot for those whole pages containing any part of the
       address space of the process starting at address addr and continuing
       for len bytes. The parameter prot determines whether read, write,
       execute, or some combination of accesses are permitted to the data
       being mapped. The prot argument should be either PROT_NONE or the
       bitwise-inclusive OR of one or more of PROT_READ, PROT_WRITE, and
       PROT_EXEC.

       If an implementation cannot support the combination of access types
       specified by prot, the call to mprotect() shall fail.

       An implementation may permit accesses other than those specified by
       prot; however, no implementation shall permit a write to succeed where
       PROT_WRITE has not been set or shall permit any access where PROT_NONE
       alone has been set. Implementations shall support at least the
       following values of prot: PROT_NONE, PROT_READ, PROT_WRITE, and the
       bitwise-inclusive OR of PROT_READ and PROT_WRITE. If PROT_WRITE is
       specified, the application shall ensure that it has opened the mapped
       objects in the specified address range with write permission, unless
       MAP_PRIVATE was specified in the original mapping, regardless of
       whether the file descriptors used to map the objects have since been
       closed.

       The implementation may require that addr be a multiple of the page size
       as returned by sysconf().

       The behavior of this function is unspecified if the mapping was not
       established by a call to mmap().

       When mprotect() fails for reasons other than [EINVAL], the protections
       on some of the pages in the range [addr,addr+len) may have been
       changed.

RETURN VALUE
       Upon successful completion, mprotect() shall return 0; otherwise, it
       shall return -1 and set errno to indicate the error.

ERRORS
       The mprotect() function shall fail if:

       EACCES The prot argument specifies a protection that violates the
              access permission the process has to the underlying memory
              object.

       EAGAIN The prot argument specifies PROT_WRITE over a MAP_PRIVATE
              mapping and there are insufficient memory resources to reserve
              for locking the private page.

       ENOMEM Addresses in the range [addr,addr+len) are invalid for the
              address space of a process, or specify one or more pages which
              are not mapped.

       ENOMEM The prot argument specifies PROT_WRITE on a MAP_PRIVATE mapping,
              and it would require more space than the system is able to
              supply for locking the private pages, if required.

       ENOTSUP
              The implementation does not support the combination of accesses
              requested in the prot argument.

       The mprotect() function may fail if:

       EINVAL The addr argument is not a multiple of the page size as returned
              by sysconf().

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       Most implementations require that addr is a multiple of the page size
       as returned by sysconf().

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mmap(), sysconf()

       The Base Definitions volume of POSIX.1-2017, <sys_mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          MPROTECT(3)
