pmap_protect(9) on FreeBSD
The text 49cbafeabe70, as FreeBSD 7.0-RELEASE, FreeBSD 6.3-RELEASE, FreeBSD 6.2-RELEASE, FreeBSD 6.1-RELEASE, FreeBSD 6.0-RELEASE, FreeBSD 5.5-RELEASE, FreeBSD 5.4-RELEASE, FreeBSD 5.3-RELEASE shipped it.
set physical page protection