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



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

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. Implementa-
       tions 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 shall 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.

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

       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 following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The [EINVAL] error above is marked EX because it is defined as an optional error in the POSIX Realtime Extension.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       mmap(), sysconf(), the Base Definitions volume of IEEE Std 1003.1-2001, <sys/mman.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003  Edition,  Standard  for
       Information  Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  MPROTECT(3P)