Process management

Other mapping functions

long
sysconf(PAGESIZE);

sysconf returns the system-dependent size of a memory page. For portability, applications should not embed any constants specifying the size of a page, and instead should make use of sysconf to obtain that information. Note that it is not unusual for page sizes to vary even among implementations of the same instruction set, increasing the importance of using this function for portability.

int
mprotect(caddr_t addr, size_t len, int prot);

mprotect has the effect of assigning protection prot to all pages in the range [addr, addr + len). The protection assigned can not exceed the permissions allowed on the underlying object. For instance, a read-only mapping to a file that was opened for read-only access can not be set to be writable with mprotect (unless the mapping is of the MAP_PRIVATE type, in which case the write access is permitted since the writes will modify copies of pages from the object, and not the object itself).