osf1 man page for mprotect

mprotect(2)							System Calls Manual						       mprotect(2)

NAME
       mprotect - Modifies access protections of memory mapping

SYNOPSIS
       #include <sys/mman.h>

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

       The following definitions of the addr parameter do not conform to current standards and are supported only for backward compatibility:

	    caddr_t addr      const void addr

STANDARDS
       Interfaces documented on this reference page conform to industry standards as follows:

       mprotect(): XSH4.2

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS
       Points  to the address of the region to be modified.  Specifies the length in bytes of the region to be modified.  Specifies access permis-
       sions as PROT_NONE or any combination of PROT_READ, PROT_WRITE, and PROT_EXEC ORed together.

DESCRIPTION
       The mprotect() function modifies the access protection of a mapped file or shared memory region. The addr and len  parameters  specify  the
       address	and  length  in  bytes	of  the  region  to  be  modified.   The  len parameter must be a multiple of the page size as returned by
       sysconf(_SC_PAGE_SIZE).	If len is not a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE), the length of the region will	be
       rounded up to the next multiple of the page size.

       The  prot  parameter  specifies the new access protection for the region.  The sys/mman.h header file defines the following access options:
       The mapped region can be read.  The mapped region can be written.  The mapped  region  can  be  executed.   The	mapped	region	cannot	be
       accessed.

       The  prot  parameter can be PROT_NONE or any combination of PROT_READ, PROT_WRITE, and PROT_EXEC ORed together.	If PROT_NONE is not speci-
       fied, access permissions may be granted to the region in addition to those explicitly requested, except	that  write  access  will  not	be
       granted unless PROT_WRITE is specified.

       If  the	region is a mapped file which was mapped with MAP_SHARED, the mprotect() function grants read or execute access permission only if
       the file descriptor used to map the file is open for reading, and grants write access permission only if the file descriptor  used  to  map
       the  file  is  open  for  writing.   If the region is a mapped file which was mapped with MAP_PRIVATE, the mprotect() function grants read,
       write, or execute access permission only if the file descriptor used to map the file is open for reading.  If the region is a shared memory
       region which was mapped with MAP_ANONYMOUS, the mprotect() function grants all requested access permissions.

       The  mprotect()	function  does	not modify the access permission of any region which lies outside of the specified region, except that the
       effect on addresses between the end of the region and the end of the page containing the end of the region is unspecified.

       If the mprotect() function fails under a condition other than that specified by [EINVAL], the access protection of some of the pages in the
       range  [addr,  addr  + len) may have been changed.  For example, if the error occurs on some page at an addr2, mprotect() may have modified
       the protections of all whole pages in the range [addr, addr2).

RETURN VALUES
       Upon successful completion, the mprotect() function returns 0 (zero).  Otherwise, mprotect() returns -1 and  sets  errno  to  indicate  the
       error.

ERRORS
       The mprotect() function sets errno to the specified values for the following conditions:

       The prot parameter specifies a protection that conflicts with the access permission set for the underlying file.  The prot parameter speci-
       fies PROT_WRITE over a MAP_PRIVATE mapping and there are insufficient memory resources to reserve for locking  the  private  page.   [Tru64
       UNIX]  Some  or all of the addresses in the range starting at addr and continuing for len bytes are locked.  [Tru64 UNIX]  The range [addr,
       addr + len) includes an invalid address.  The prot parameter is invalid, or the addr parameter is not  a  multiple  of  the  page  size	as
       returned  by  sysconf(_SC_PAGE_SIZE).   [Tru64  UNIX]  Addresses  in  the  range  [addr, addr + len) are invalid for the address space of a
       process, or specify one or more unmapped pages.

	      [Tru64 UNIX]  A system resource was exhausted or a system limit was exceeded.  The most common case occurs when the calling  process
	      exceeds  the  kernel configuration parameter VPAGEMAX.  This limit specifies the maximum number of pages per process that can reside
	      in regions of contiguous virtual address space which have mixed page protections.  The system administrator can override the default
	      VPAGEMAX	value  by  setting  the  vpagemax  nnn option in the system configuration file, then reconfiguring the kernel, and finally
	      rebooting the system.

RELATED INFORMATION
       Functions: getpagesize(2), mmap(2), msync(2), sysconf(3)

       Standards: standards(5) delim off

																       mprotect(2)