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 correspond-
       ing 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  fol-
       lowing  values of prot: PROT_NONE, PROT_READ, PROT_WRITE, and the bitwise-inclusive OR of PROT_READ and PROT_WRITE. If PROT_WRITE is speci-
       fied, 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 Technol-
       ogy -- 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 original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003							      MPROTECT(3P)