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Linux 2.6 - man page for mprotect (linux section 3posix)

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

       mprotect - set protection of memory mapping

       #include <sys/mman.h>

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

       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

       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 shall require that addr be a multiple of the page size as  returned  by

       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.

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

       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.

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

       The following sections are informative.


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



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

       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, Copyright (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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003				      MPROTECT(P)

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