mprotect()

Change memory protection

Synopsis:

#include <sys/mman.h>

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

Library:

libc

Description:

The mprotect() function changes the access protections on any mappings residing in the range starting at addr, and continuing for len bytes.

The prot parameter specifies the new access capabilities to the mapped memory region(s). The bits that can be combined in this field are defined in <sys/mman.h> and listed below:

PROT_EXEC

The region can be executed.

PROT_NOCACHE

Disable caching of the region (for example, can be used to access dual ported memory).

PROT_NONE

The region can't be accessed.

PROT_READ

The region can be read.

PROT_WRITE

The region can be written.

Returns:

0

Success.

-1

An error occurred (errno is set).

If mprotect() fails, the protections on some of the pages in the address range starting at addr and continuing for len bytes may have been changed.

Errors:

EACCES

The memory object wasn't opened for read, regardless of the protection specified.

The memory object wasn't opened for write, and PROT_WRITE was specified for a MAP_SHARED type mapping.

EAGAIN

The prot argument specifies PROT_WRITE on a MAP_PRIVATE mapping and there's insufficient memory resources to reserve for locking the private pages (if required).

ENOMEM

The addresses in the range starting at addr and continuing for len bytes are outside the range allowed for the address space of a process, or specify one or more pages that are not mapped.

The prot argument specifies PROT_WRITE on a MAP_PRIVATE mapping, and locking the private pages (if required) would need more space than the system can supply to reserve for doing so.

ENOSYS

The function mprotect() isn't supported by this implementation.

Classification:

POSIX 1003.1 (Realtime Extensions)

See also:

errno, mmap(), munmap(), shm_open(), shm_unlink()