[Valgrind-developers] valgrind --track-fds, fuse and other issues

[Mark W. <ma...@kl...>]

Hi,

At the Cauldron "Using the Valgrind error manager for file descriptor
tracking" talk
https://gcc.gnu.org/wiki/cauldron2024#cauldron2024talks.using_the_valgrind_error_manager_for_file_descriptor_tracking
there were various questions and suggestions. I added several to bugzilla:

Add bad fd usage errors for --track-fds in ML_(fd_allowed)
https://bugs.kde.org/show_bug.cgi?id=493418
Add --track-fds=bad mode (no "leak" tracking)
https://bugs.kde.org/show_bug.cgi?id=493434
Add a new fds only mode to --track-fds
https://bugs.kde.org/show_bug.cgi?id=493433
Review all syscalls (and ioctls) that use or return (new) file descriptors
https://bugs.kde.org/show_bug.cgi?id=493430

There was also a question about using valgrind on a program that
implements a fuse file system, like the new glibc test support helper
by Florian. I didn't give a very good answer to that one. Because I
forgot that valgrind already should be able to handle that. Valgrind
obviously already has to handle blocking syscalls that could be
unblock by another thread. There is a "sim hint" to extend this to
syscalls that might block when the underlying file system managed by
the program itself.

   --sim-hints=hint1,hint2,...
       Pass miscellaneous hints to Valgrind which slightly modify the
       simulated behaviour in nonstandard or dangerous ways, possibly to
       help the simulation of strange features. By default no hints are
       enabled. Use with caution! Currently known hints are:

[...]

       •   fuse-compatible: Enable special handling for certain system
           calls that may block in a FUSE file-system. This may be
           necessary when running Valgrind on a multi-threaded program
           that uses one thread to manage a FUSE file-system and another
           thread to access that file-system.

Please let me know if this still doesn't work. This hint hasn't been
updated in a long time and there might be some newer syscalls that
should enable this hint, but don't (yet).

Cheers,

Mark