[CRIU] CRIU ARM branch

[Cyrill Gorcunov]

On Wed, Dec 12, 2012 at 05:34:10PM +0400, alekskartashov at parallels.com wrote:
> Dear colleagues,
> 
> This patchset implements the ARM support in CRIU.
> 
> Known issues:
> 
> * The following tests fail in the ARM version:
>   - static/pty03,
>   - transition/file_read,
>   - static/file_fown,
>   - static/ipc_namespace,
>   - static/ipc.
> 
> * The test static/session01 contains x86-specific lock operations so it has to be excluded
>   while testing on ARM.
> 
> * The test static/futex segfaults when the program crtools is compiled with the switch -O2.
> 
> 
> This patchset takes into account notes by Pavel Emelyanov about the previous version
> of the patchset:
> 
> * Keep the current x86-specific build scripts intact.
> * Fix all compilation warnings in the ARM branch.

Alexander, before anything else, could you please describe the main problems
between ARM code and x86-64 code which you had to resolve in attempt to
implemtent c/r on this architecture?

As far as I can tell (out from ARM platforms zoo, which now even start to
include ARM64 cpus, what a suprise ;) the main differences are (correct
me please, if I make a mistake somewhere)

 - ARM port is for 32 bit cpu with bi-endianing, which means it may be either LE or BE,
   depending on particular settings, right? By LE/BE I mean little-ending or
   big-ending byte ordering in words and such, at moment you'are targeting LE
   order

 - since it's 32 bit arch, you need to define u64 somewhere separately from our
   types.h file

 - this as well force you to check if %lx format for pr_ helpers were used
   corectly and if not you had to fix it up

 - in image file the registers had to be converted to new set which is suitable
   for ARM machines

 - some explanations about what have been done to parasite code and restorer
   code (how rt_sigreturn frame looks on ARM).

I mean it would be a way more convenient if you describe what hardness you met
during porting procedure and what had you to do to resolve it, in big picture.

	Cyrill