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 .