freebsd man page for mprotect

MPROTECT(2)						      BSD System Calls Manual						       MPROTECT(2)

NAME
     mprotect -- control the protection of pages

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <sys/mman.h>

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

DESCRIPTION
     The mprotect() system call changes the specified pages to have protection prot.  Not all implementations will guarantee protection on a page
     basis; the granularity of protection changes may be as large as an entire region.	A region is the virtual address space defined by the start
     and end addresses of a struct vm_map_entry.

     Currently these protection bits are known, which can be combined, OR'd together:

     PROT_NONE	 No permissions at all.
     PROT_READ	 The pages can be read.
     PROT_WRITE  The pages can be written.
     PROT_EXEC	 The pages can be executed.

RETURN VALUES
     The mprotect() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate the error.

ERRORS
     The mprotect() system call will fail if:

     [EINVAL]		The virtual address range specified by the addr and len arguments is not valid.

     [EACCES]		The calling process was not allowed to change the protection to the value specified by the prot argument.

SEE ALSO
     madvise(2), mincore(2), msync(2), munmap(2)

HISTORY
     The mprotect() system call first appeared in 4.4BSD.

BSD
								   June 9, 1993 							       BSD