MPROTECT(2)               FreeBSD 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(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.

     In addition to these protection flags, FreeBSD provides the ability to
     set the maximum protection of a region (which prevents mprotect from
     upgrading the permissions).  This is accomplished by or'ing one or more
     PROT_ values wrapped in the PROT_MAX() macro into the prot argument.

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 indicate the
     error.

ERRORS
     The mprotect() system call will fail if:

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

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

     [EINVAL]           The prot argument contains unhandled bits.

     [ENOTSUP]          The prot argument contains permissions which are not a
                        subset of the specified maximum permissions.

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

HISTORY
     The mprotect() system call was first documented in 4.2BSD and first
     appeared in 4.4BSD.

     The PROT_MAX functionality was introduced in FreeBSD 13.

FreeBSD 13.1-RELEASE-p6        February 26, 2020       FreeBSD 13.1-RELEASE-p6