mprotect()

change memory protection

Synopsis:

#include <sys/mman.h>
int mprotect( void *addr, size_t len, 
              int prot );

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 are described in the Header Files chapter.

Returns:

Zero. On error, -1 is returned and errno is set.

If the mprotect() function fails for reasons other than EINVAL, 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 are insufficient memory resources to reserve for locking the private pages (if required).

EINVAL

The value of addr isn't a multiple of the page size as returned by the sysconf() function for _SC_PAGESIZE.

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 aren't 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 1003.4

See also:

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