On Tue, Jan 27, 2015 at 11:50:49AM -0800, Kees Cook wrote: > On Tue, Jan 27, 2015 at 1:41 AM, Cyrill Gorcunov <gorcu...@openvz.org> wrote: > > Signed-off-by: Cyrill Gorcunov <gorcu...@openvz.org> > > CC: Kees Cook <keesc...@chromium.org> > > CC: Andrew Morton <a...@linux-foundation.org> > > CC: "Kirill A. Shutemov" <kir...@shutemov.name> > > CC: Calvin Owens <calvinow...@fb.com> > > CC: Alexey Dobriyan <adobri...@gmail.com> > > CC: Oleg Nesterov <o...@redhat.com> > > CC: "Eric W. Biederman" <ebied...@xmission.com> > > CC: Al Viro <v...@zeniv.linux.org.uk> > > CC: Peter Feiner <pfei...@google.com> > > CC: Pavel Emelyanov <xe...@openvz.org> > > --- > > > > Gentlemen, could you please take a look once time permit. > > Which questions this text raises so I could add more info > > here (how we use it in criu, ptrace_may_access guards?) > > > > Documentation/filesystems/proc.txt | 23 +++++++++++++++++++++++ > > 1 file changed, 23 insertions(+) > > > > Index: linux-2.6.git/Documentation/filesystems/proc.txt > > =================================================================== > > --- linux-2.6.git.orig/Documentation/filesystems/proc.txt > > +++ linux-2.6.git/Documentation/filesystems/proc.txt > > @@ -42,6 +42,7 @@ Table of Contents > > 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm > > 3.7 /proc/<pid>/task/<tid>/children - Information about task children > > 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file > > + 3.9 /proc/<pid>/map_files - Information about memory mapped files > > > > 4 Configuring procfs > > 4.1 Mount options > > @@ -1763,6 +1764,28 @@ pair provide additional information part > > with TIMER_ABSTIME option which will be shown in 'settime flags', > > but 'it_value' > > still exhibits timer's remaining time. > > > > +3.9 /proc/<pid>/map_files - Information about memory mapped files > > +--------------------------------------------------------------------- > > +This directory consists of simbolic links which represent memory mapped > > files > > +the process is carrying. A typical output is like the following > > + > > + | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> > > /usr/lib64/ld-2.18.so > > + | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> > > /usr/lib64/ld-2.18.so > > + | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> > > /usr/lib64/ld-2.18.so > > + | ... > > + | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> > > /usr/lib64/libselinux.so.1 > > + | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls > > + > > +The name of a link is virtual memory bounds a particular map exhibits, i.e. > > +vm_area_struct::vm_start-vm_area_struct::vm_end. > > + > > +The main purpose of map_files directory is to be able to retrieve a set of > > +memory mapped files in a fast way instead of parsing /proc/<pid>/maps or > > +/proc/<pid>/smaps which contain a way more records. Same time one can > > open(2) > > +mappings from the listings of two processes and comparing inodes figure out > > +which anonymous memory areas are actually shared. > > Thanks for details! I still don't understand how this is used for > checkpoint/restore when the mmap offset isn't shown. Can't a process > map, say 4K of a file, from different offsets, and it would show up > as: > > 400000-401000 -> /some/file > 401000-402000 -> /some/file > > but there'd be no way to know how to restore that mapping?
IIUC, it's complementry to data in maps/smap. If the file was closed and unlinked, it's the only way to get file descriptor which points the inode under mapping. -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
