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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 (consult 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, exe-
       cute, 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  follow-
       ing  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 map-
              ping 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  sup-
              ply 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.1-2008, <sys_mman.h>
COPYRIGHT
       Portions of this text are reprinted and reproduced in  electronic  form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal and Electronics Engineers,  Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical Corrigendum 1 applied.) 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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                         MPROTECT(3P)