Early Draft: Add parameter to check if files are mapped in processes not part of the recording.

[bernhardu]

In its current state it just calls lsof with the pids inside the the recording excluded.

It would show the mapping that caused the issue in #3417, but the others are probably just read-only mappings due to /proc/pid/maps.

$ rr record --lsof -n atril sshfs/home/benutzer/test2.pdfrr: Saving execution to trace directory `/home/bernhard/data/entwicklung/2022/rr/rr-recordings/atril-14'.
Warning: /usr/lib/x86_64-linux-gnu/gconv/gconv-modules.cache seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /home/bernhard/.cache/fontconfig/a6050266-6adb-4e1c-8a1d-f55d18a3f9c3-le64.cache-7 seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /run/user/1000/dconf/user seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /home/bernhard/.local/share/mime/mime.cache seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /usr/local/share/mime/mime.cache seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /usr/share/mime/mime.cache seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /home/bernhard/.local/share/gvfs-metadata/root seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
Warning: /home/bernhard/.local/share/gvfs-metadata/root-5c301c7a.log seems to be mapped by a process outside of the recording. Diversions might happen when replaying this trace.
...

[bernhardu]

The call to system() might be ugly to dangerous. lsof seems to want in the long term to make it available as library. Would the license allow it?

[rocallahan]

This would be a cool feature to have but rather than calling lsof I think we would want to reimplement the functionality by scanning /proc/.../maps.

[bernhardu]

Rebased and removed the ugly lsof system call by manually iterating through /proc/.../maps. Command line option might need another name now.

[bernhardu]

Rebased and renamed the parameter from --lsof to --check-outside-mmaps.

Or is this something we want to activate generally?

[bernhardu]

Small addition, return after first process is found with outside mapping and message got printed.

Global activation would succeed with the test suite except test mmap_self_maps_shared.

[bernhardu]

• Replaced the system function call by fork+execve.
• Add timeout to the test executable, to avoid it runs forever.

I made some tests to activate it generally. This would at least not work for 32-bit rr running at a 64-bit kernel, because the KernelMapIterator does not like higher bitnesses than it being compiled for. Also the mmap_self_maps_shared test would trigger for files libc.so.6, libdl.so.2, ld-linux-x86-64.so.2, if used generally.

[bernhardu]

• Skip test when running a force32bit build on a 64-bit system.
• Add fatal message when running a force32bit build on a 64-bit system.
• Simplify by using Session::find_task.
• Fixed break, which left the check when the first traced process was reached.
• Change comparison from filename to device and inode.