mprotect - modify access protection for memory mapping

Syntax

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

Syntax	#include <sys/mman.h> int mprotect(void *addr, size_t len, int prot);
Description	The mprotect() function changes the access permissions for the mappings in the [addr, addr + len) area to the access permission specified in prot. The value specified in len is rounded to a multiple of the page size specified by sysconf(). All values that can also be specified in mmap() are permissible for prot. The values for prot are defined in sys/mman.h as follows:
	PROT_READ	Page can be read.
	PROT_WRITE	Page can be written.
	PROT_EXEC	Page can be executed.
	PROT_NONE	Page cannot be accessed.
	If mprotect() fails but the reason is not EINVAL, it may be that the access permissions of some pages were already changed in the specified area [addr, addr + len). If the error is in the address addr2, the access permissions of all whole pages in the area [addr, addr2] will be changed.
Return val.	0	if successful.
	-1	if an error occurs. errno is set to indicate the error.
Errors	Under the conditions described below, the mprotect() function will fail and set errno to the following values:
	EACCES	prot contains a value that does not match the access permissions of the process for the underlying file.
	EAGAIN	prot contains the value PROT_WRITE for a mapping of type MAP_PRIVATE and a memory bottleneck occurs, i.e. the storage resources for reserving and locking the private page are not sufficient.
	EINVAL	addr is not a multiple of the page size specified by sysconf(), or the len argument contains a value less than or equal to 0.
	ENOMEM	Addresses in the area [addr, addr + len) are invalid for the address area of the process, or one or more pages have been specified which are not mapped.
See also	mmap(), sysconf(), sys/mman.h.