[GSoC] Making vkernels checkpointable - week 11

[Pawel Dziepak]

Hello,

Last week I continued improving checkpointing code and introduced some
enhacnements I've already mentioned earlier but did not implement
until now. When reading a checkpoint file, if an unrecognized ELF note
is encountered it is simply ignored instead of failing. That would
allow to add any additional data to the checkpoint files and keep the
older versions of the kernel still able to restore process from such
file. Moreover, the two notes that keep version information
NT_PRPSINFO and NT_PRSTATUS are allowed to be bigger than expected
thus making it possible for a new kernel to properly interpret the
older checkpoint files.

Apart from that, I spent some time solving the outstanding issues with
restored virtual processes. As I expected, explicitly calling
vmspace_ctl() in the SIGCKPT[EXIT] signal handler wasn't necessary.
There are still problems with switching threads and timers, though.
That's what I am going to work on this week.

Paweł