Hi Lorenzo, On Mon, Dec 02, 2024 at 04:58:29PM +0000, Lorenzo Stoakes wrote: > Lightweight guard region support has been added to Linux 6.13, which adds > MADV_GUARD_INSTALL and MADV_GUARD_REMOVE flags to the madvise() system > call. Therefore, update the manpage for madvise() and describe these > operations. > > Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx> Thanks for the patch! A few minor comments below. > --- > v3: > * Don't describe SIGSEGV as a fatal signal as per Jann. > > v2: > * Updated to use semantic newlines as suggested by Alejandro. > * Avoided emboldening parens as suggested by Alejandro. > * One very minor grammatical fix. > https://lore.kernel.org/all/20241129155943.85215-1-lorenzo.stoakes@xxxxxxxxxx > > v1: > https://lore.kernel.org/all/20241129093205.8664-1-lorenzo.stoakes@xxxxxxxxxx > > man/man2/madvise.2 | 93 ++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 93 insertions(+) > > diff --git a/man/man2/madvise.2 b/man/man2/madvise.2 > index 4f2210ee2..4cb5e7302 100644 > --- a/man/man2/madvise.2 > +++ b/man/man2/madvise.2 > @@ -676,6 +676,91 @@ or secret memory regions created using > Note that with > .BR MADV_POPULATE_WRITE , > the process can be killed at any moment when the system runs out of memory. > +.TP > +.BR MADV_GUARD_INSTALL " (since Linux 6.13)" > +Install a lightweight guard region into the range specified by > +.I addr > +and > +.IR size , > +causing any read or write in the range to result in a > +.B SIGSEGV > +signal being raised. > +.IP > +If the region maps memory pages they will be cleared as part of the operation, > +though if > +.B MADV_GUARD_INSTALL > +is applied to regions containing pre-existing lightweight guard regions, > +they are left in place. > +.IP > +This operation is only supported for writable anonymous private mappings which > +have not been mlock'd. > +An > +.B EINVAL > +error is returned if it is attempted on any other kind of mapping. > +.IP > +This operation is more efficient than mapping a new region of memory > +.BR PROT_NONE , > +as it does not require the establishment of new mappings, > +instead regions of an existing mapping simply have their page tables > +manipulated to establish the desired behavior. > +No additional memory is used. > +.IP > +Lightweight guard regions remain on fork > +(except for any parts which have had > +.B MADV_WIPEONFORK > +applied to them), > +and are not removed by > +.BR MADV_DONTNEED , > +.BR MADV_FREE , > +.BR MADV_PAGEOUT , > +or > +.BR MADV_COLD . > +.IP > +Attempting to > +.BR mlock () We should specify the chapter in the manual: (2) > +lightweight guard regions will fail, > +as will > +.B MADV_POPULATE_READ > +or > +.BR MADV_POPULATE_WRITE . > +.IP > +If the mapping has its attributes changed, > +or is split or partially unmapped, > +any existing guard regions remain in place > +(except if they are unmapped). > +.IP > +If a mapping is moved using > +.BR mremap (), Same here. > +lightweight guard regions are moved with it. > +.IP > +Lightweight guard regions are removed when unmapped, > +on process teardown, > +or when the > +.B MADV_GUARD_REMOVE > +operation is applied to them. > +.TP > +.BR MADV_GUARD_REMOVE " (since Linux 6.13)" > +Remove any lightweight guard regions which exist in the range specified by > +.I addr > +and > +.IR size . > +.IP > +All mappings in the range other than lightweight guard regions are left in place > +(including mlock'd mappings). > +The operation is, > +however, > +only valid for writable anonymous private mappings, Wouldn't it be better to say "valid only" instead of "only valid"? (Non-native speaker here, though.) Have a lovely night! Alex > +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. > +.IP > +If any transparent huge pages are encountered in the operation, > +they are left in place. > .SH RETURN VALUE > On success, > .BR madvise () > @@ -787,6 +872,14 @@ or > or secret memory regions created using > .BR memfd_secret(2) . > .TP > +.B EINVAL > +.I advice > +is > +.B MADV_GUARD_INSTALL > +or > +.BR MADV_GUARD_REMOVE , > +but the specified address range contains an unsupported mapping. > +.TP > .B EIO > (for > .BR MADV_WILLNEED ) > -- > 2.47.1 -- <https://www.alejandro-colomar.es/>
Attachment:
signature.asc
Description: PGP signature
