We have a bug. If someone opens proc with open_pid_proc or alike
with PROC_SELF of real PID before going to restore fds, then the
fd cached by proc helpers would be cached in fd 0 (we close all
fds beforehead) and it may clash with restored fds.

We don't hit this right now simply due to being too lucky -- we
call open_proc(PROC_GEN) on "locks" which first closes the cached
the per-pid descriptor and then reports back just the /proc one
which sits in service area.

But once we change this (next patch) things would get broken.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

We have a, well, issue with how we calculate the vma's mnt_id.

Right now get one via criu side file descriptor that it got by
opening the /proc/pid/map_files/ link. The problem is that these
descriptors are 'merged' or 'borrowed' by adjacent vmas from
previous ones. Thus, getting the mnt_id value for each of them
makes no sense -- these files are the same.

So move this mnt_id getting earlier into vma parsing code. This
brings a potential problem -- if we have two adjacent vmas
mapping the same inode (dev:ino pair) but living in different
mount namespaces -- this check would produce wrong result.
"Wrong" from the perspective that on restore correct file would
be opened from wrong namespace.

I propose to live with it, since this is not worse than the
--evasive-devices option, it's _very_ unlikely, but saves a lot
of openeings.

Note, that in case app switched mount namespace and then mapped
some new library (with dlopen) things would work correctly -- new
vmas will likely be not adjacent and for different dev:ino.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

We have non-obvious handling of vm_file_fd/vm_socket_id
pair and the vma->file_borrowed.

Comment these to in the structure.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

We have some fields, that are dump-only and some that
are restore only (quite a lot of them actually).

Reshuffle them on the vma_area to explicitly show which
one is which. And rename some of them for easier grep.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Reported-by: Mr Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Currently this optimization skips unscanned data
and doesn't work. Lets skip scanned data only.

Reported-by: Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

This sounds strange, but we kinda need one. Here's the
justification for that.

We heavily open /proc/pid/foo files. To speed things up we
do pid_dir = open("/proc/pid") then openat(pid_dir, foo).
This really saves time on big trees, up to 10%.

Sometimes we need line-by-line scan of these files, and for
that we currently use the fdopen() call. It takes a file
descriptor (obtained with openat from above) and wraps one
into a FILE*.

The problem with the latter is that fdopen _always_ mmap()s
a buffer for reads and this buffer always (!) gets unmapped
back on fclose(). This pair of mmap() + munmap() eats time
on big trees, up to 10% in my experiments with p.haul tests.

The situation is made even worse by the fact that each fgets
on the file results in a new page allocated in the kernel
(since the mapping is new). And also this fgets copies data,
which is not big deal, but for e.g. smaps file this results
in ~8K bytes being just copied around.

Having said that, here's a small but fast way of reading a
descriptor line-by-line using big buffer for reducing the
amount of read()s.

After all per-task fopen_proc()-s get reworked on this engine
(next 4 patches) the results on p.haul test would be

        Syscall     Calls      Time (% of time)
Now:
           mmap:      463  0.012033 (3.2%)
         munmap:      447  0.014473 (3.9%)
Patched:
         munmap:       57  0.002106 (0.6%)
           mmap:       74  0.002286 (0.7%)

The amount of read()s and open()s doesn't change since FILE*
also uses page-sized buffer for reading.

Also this eliminates some amount of lseek()s and fstat()s
the fdopen() does every time to catch up with file position
and to determine what sort of buffering it should use (for
terminals it's \n-driven, for files it's not).
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

The main reason for this is -- dumping namespace has a lot of
points when the process just waits for something. At the same
time criu process wait for the ns dumper and doesn't dump
others.

The great example of waiting for something is setns syscall.
Very often it calls synchronize_rcu() which can be quite long.
Let other processes do smth useful while this.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Andrew Vagin <avagin@parallels.com>

Unless we seek and re-read the PB images, the only way I can see to do this is
to keep a list of the previously seen dead pids and check if a new remap is in
that list.
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

We can't remap these files correctly anyway, so we should just return success
if we find one of these files to remap.

v2: don't try to remap accessible files in /proc
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

We currently have all mouninfo-s from all mnt namespaces collected
in one big list. On dump we scan through it to find the namespaces
we need to dump.

This can be optimized by walking the list of namespaces instead.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Andrew Vagin <avagin@parallels.com>

Fix compilation on ARM:
pie/restorer.c: In function ‘wait_helpers’:
pie/restorer.c:728:3: error: implicit declaration of function ‘sys_waitpid’ [-Werror=implicit-function-declaration]
cc1: all warnings being treated as errors

Reported-by: Mr Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Andrey Vagin <avagin@parallels.com>

Unfortunately the kernel doesn't flush hw breakpoints on
detaching ptrace. If a breakpoint is triggered without ptrace, it
will be killed by SIGTRAP.

Reported-by: Mr Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Since we now can return port to user in autobind case, it's ok to request
page-server without setting ps_info.
Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

On restore parasite_stop_on_syscall() can be called after PTRACE_SYSCALL
and after a breakpoint. parasite_stop_on_syscall() must be called only
after PTRACE_SYSCALL, so all tests where is one process stuck.

Reported-by: Mr Jenkins
Signed-off-by: Andrew Vagin <avagin@openvz.org>
Acked-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Here is a race now:
./zdtm.sh --ct -d -C -x static/cgroup02 ns/static/pipe02 &> ns_static_pipe02.log || \
{ flock Makefile cat ns_static_pipe02.log; exit 1; }
./zdtm.sh --ct -d -C -x static/cgroup02 ns/static/busyloop00 &> ns_static_busyloop00.log || \
{ flock Makefile cat ns_static_busyloop00.log; exit 1; }
make[3]: `zdtm_ct' is up to date.
mkdir: cannot create directory ‘zdtm.GgIjUS/holder’: File exists

Reported-by: Mr Jenkins
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Currently CRIU traces syscalls to catch a moment, when sigreturn() is
called. Now we trace recv(cmd), close(logfd), close(cmdfd), sigreturn().

We can reduce a number of steps by using hw breakpoints. A breakpoint is
set before sigreturn, so we will need to trace only it.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Currently CRIU traces syscalls to catch a moment, when sigreturn() is
called. Now we trace recv(cmd), close(logfd), close(cmdfd), sigreturn().

We can reduce a number of steps by using hw breakpoints. A breakpoint is
set before sigreturn, so we will need to trace only it.

v2: In the first version a breakpoint is set after sigreturn. In this
case we have a problem with signals. If a process has pending signals,
it will start to precess them after exiting from sigreturn(), but before
returning to userspace. So the breakpoint will not be triggered.

And at the end Here are a few numbers how we catch sigreturn.
Before this patch criu executes 36 syscalls and gets 12 signals.
With this patch criu executes 18 syscalls and gets 5 signals.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

The control socket has enough buffer for one command and the target
process will not wait a new command, so we will avoid extra context
switches.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Test maps 17 pages and mlocks them, then changes user id from root
to 18943, after c/r checks that MAP_LOCKED bit is set for that vma.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Tikhomirov <ptikhomirov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

If a file like /proc/20/mountinfo is open, but 20 is a zombie (or doesn't exist
any more), we can't read this file at all, so a link remap won't work. Instead,
we add a new remap, called the dead process remap, which forks a TASK_HELPER as
that dead pid so that the restore task can open the new /proc/20/mountinfo
instead.

This commit also adds a new stage CR_STATE_RESTORE_SHARED. Since new
TASK_HELPERS are added when loading the shared resource images, we need to wait
to start forking tasks until after these resources are loaded.

v2: fix a mutex bug
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

In order to use TASK_HELPERS to open files from dead processes, they should
persist until criu is done restoring the filesystem, which happens in the
RESTORE stage. To do this, we need to pass each helper's PIDs to the restorer
blob, so that it can wait() on them when the restore stage is done.

This commit is in preparation for the remap_dead_pid commits.

v2: wait() on helpers after restore stage is over
v3: add CR_STATE_RESTORE_FS stage
v4: CR_STATE_RESTORE_FS waits for nr_tasks + nr_helpers, not nr_threads
v5: ditch CR_STATE_RESTORE_FS in favor of passing helpers to restorer blob
Signed-off-by: Tycho Andersen <tycho.andersen@canonical.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Currently here is a bug, because when we see criu's mount namespace,
we go to the "out" mark and don't validate mounts.
Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

The same reasoning as for personality file -- switch to
plan open + read + close.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

It turned out, that fdopen (used in fopen_proc) always maps
a 4k buffer for reads and this buffer gets unmap-ed later
on fclose.

Taking into account the amount of proc files we read (~20
per task plus one file per opened file descriptor) this
mmap+munmap result in quite a lot of useless CPU time.

E.g. for a container of 20 tasks we have 1000 calls taking
~8% of total dump time.

So lets first stop doing this for simple cases -- one line
proc files.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

So it won't depend on the order in declaration.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

They don't change these objects, so can share them
with parent (will be created slightly faster :) ).

The plan is to make them CLONE_VM, but it's not that
easy.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

When clone-ing kids we can set their stack on current, as
it will anyway be COW-ed later. One thing to note -- we do
need to reserve some space on the stack for glibc's arguments
and retcode allocation. 128 bytes should be enough for 16
pointers while clone has 5 arguments.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>