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mprotect()

Change memory protection

Synopsis:

#include <sys/mman.h>

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

Arguments:

addr

The beginning of the range of addresses whose protection you want to change.

len

The length of the range of addresses, in bytes.

prot

The new access capabilities for the mapped memory region(s). You can combine the following bits, which are defined in <sys/mman.h>:

• PROT_EXEC -- the region can be executed.
• PROT_NOCACHE -- disable caching of the region (for example, 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.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

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

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 MPR

See also:

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