Provided by: freebsd-manpages_8.0-1_all
mprotect - control the protection of pages
Standard C Library (libc, -lc)
mprotect(const void *addr, size_t len, int prot);
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
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.
The mprotect() function returns the value 0 if successful; otherwise the
value -1 is returned and the global variable errno is set to indicate the
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
madvise(2), mincore(2), msync(2), munmap(2)
The mprotect() system call first appeared in 4.4BSD.