From: Lorenzo Stoakes Date: Wed, 23 Apr 2025 18:31:05 +0000 (+0100) Subject: man/man2/madvise.2: Update MADV_GUARD_INSTALL, MADV_GUARD_REMOVE for Linux 6.15 X-Git-Tag: man-pages-6.14~14 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9ee66d0b01dfc797c57b4735fd48c138f97a66d2;p=thirdparty%2Fman-pages.git man/man2/madvise.2: Update MADV_GUARD_INSTALL, MADV_GUARD_REMOVE for Linux 6.15 Lightweight guard region support has been extended in Linux 6.15, permitting the use of these features for file-backed and read-only mappings. Update the description for these operations in the madvise manpage to describe the changed behaviour. Signed-off-by: Lorenzo Stoakes Message-ID: <20250423183105.116978-1-lorenzo.stoakes@oracle.com> Signed-off-by: Alejandro Colomar --- diff --git a/man/man2/madvise.2 b/man/man2/madvise.2 index bd2b90b7a..be1ba17ae 100644 --- a/man/man2/madvise.2 +++ b/man/man2/madvise.2 @@ -697,9 +697,24 @@ is applied to regions containing pre-existing lightweight guard regions, they are left in place. .IP -This operation is supported -only for writable anonymous private mappings -which have not been mlock'd. +Prior to Linux 6.15, +this operation was supported +only for writable anonymous private mappings. +Since Linux 6.15, +both anonymous and file-backed mappings are supported, +including read-only mappings. +.IP +The mapping must not be mlock'd, +map hugetlb ranges, +nor contain special mappings. +For example, +mappings marked with kernel-internal flags such as +.B VM_PFNMAP +or +.BR VM_IO , +or secret memory regions created using +.BR memfd_secret (2). +.IP An .B EINVAL error is returned if it is attempted on any other kind of mapping. @@ -756,19 +771,23 @@ and .IP All mappings in the range other than lightweight guard regions -are left in place -(including mlock'd mappings). -The operation is, -however, -valid only for writable anonymous private mappings, +are left in place. +The operation is supported on those mappings +permitted by +.B MADV_GUARD_INSTALL +in addition to mlock()'d mappings, returning an .B EINVAL error otherwise. .IP When lightweight guard regions are removed, they act as empty regions of the containing mapping. -Since only writable anonymous private mappings are supported, -they therefore become zero-fill-on-demand pages. +Therefore, +anonymous private mappings become +zero-fill-on-demand pages, +and file-backed mappings are repopulated with the +memory contents from the up-to-date contents of the +underlying mapped file. .IP If any transparent huge pages are encountered in the operation, they are left in place.