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 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 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 original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .