MPROTECT(2) BSD System Calls Manual MPROTECT(2)
mprotect -- control the protection of pages
mprotect(void *addr, size_t len, int prot);
The mprotect() system call sets the access protections for the pages that
contain the address range addr through addr + len - 1 (inclusive). If
len is 0, no action is taken on the page that contains addr.
The protections (region accessibility) are specified in the prot argu-
ment. It should either be PROT_NONE (no permissions) or the bitwise OR
of one or more of the following values:
PROT_EXEC Pages may be executed.
PROT_READ Pages may be read.
PROT_WRITE Pages may be written.
Not all implementations will guarantee protection on a page basis; the
granularity of protection changes may be as large as an entire region.
Nor will all implementations guarantee to give exactly the requested per-
missions; more permissions may be granted than requested by prot. How-
ever, if PROT_WRITE was not specified then the page will not be writable.
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
mprotect() will fail if:
[EACCES] The process does not have sufficient access to the
underlying memory object to provide the requested pro-
[ENOMEM] The process has locked future pages with
mlockall(MCL_FUTURE), a page being protected is not
currently accessible, and making it accessible and
locked would exceed process or system limits.
[EINVAL] The prot argument is invalid or the specified address
range would wrap around.
madvise(2), mincore(2), msync(2), munmap(2)
The mprotect() function conforms to IEEE Std 1003.1-2008 (``POSIX.1'').
The mprotect() function first appeared in 4.4BSD.
The OpenBSD implementation of mprotect() does not require addr to be
page-aligned, although other implementations may.
BSD July 2, 2014 BSD