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, 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(3POSIX)