[patch] Support live PIDs with deleted files

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

Hi Mark,

jankratochvil/deleted

with the new /proc/PID/map_files/ feature it is possible to fully access even
deleted executable + shared_libraries.  Current Linux kernels (3.11.10) permit
on root user as the tracer but (1) hopefully it gets fixed in the future and
(2) at least for the use in ABRT it is OK as backtracer is run from core
dumping hook.

Linux kernels have always supported also /proc/PID/exe which works for deleted
main executable.  It even works for non-root users.  But it works only for the
executable, not for shared libraries.  I find more useful to push for Linux
kernel /proc/PID/map_files/ permissions fix than to implement /proc/PID/exe.

If the running binary has been upgraded while it is still running its separate
debug info files in /usr/lib/debug/ will no longer match.  But still
.eh_frame-based unwind is possible using /proc/PID/map_files/ that time.

Testcase is skipped when /proc/PID/map_files/ gives permission error.

OK for check-in?

I am not completely sure setting just mod->main.name is right but it looks so.


Thanks,
Jan
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