VM kernel crash may crash marionnet itself

[Franck Butelle]

When playing with new VM kernels (compiled with ARCH=um), we made a 64 bits kernel...
we tryied to run it with a VM in 32 bits... silly idea ! Of course the VM crashed but surprisingly
marionnet also crashed in less than a second. The debug option only showed "terminated", has if marionnet
have been killed by some regular signal. (Marionnet version 0.90.6).

[Luca Saiu (saiu)]

The issue is subtle, and I can't reproduce the problem without using UML; the example below works fine on my 64 bit machine. Notice that I tried both Unix.system and Unix.create_process, with the interprerter, the bytecode compiler, and the native compiler.

[Luca Saiu (saiu)]

I've run gdb several times on the native program (gdb --args marionnet.native); the signal (it's a SIGTERM) always arrived during a select call, when I tested (but not always from a death_monitor function, as in the attached log). This is not very significant anyway, since select can be used as a high-resolution sleep.

sysdeps/unix/syscall-template.S is part of the libc sources. It would be nice to start UML under a debugger, to see the point where it sends a signal to its parent...