Re: [Qemu-devel] linux-user: enabling binfmt P flag

[Paolo Bonzini]

Il 01/09/2014 11:12, Peter Maydell ha scritto:
>> We'd just add Ps and we'd be fine.
> 
> But this would break all your existing users' existing
> chroot setups. That's the question I'm after an answer to:
> what do you (as a distro) think would be acceptable as
> transitional breakage, if anything?

Yes, but it's not like Fedora'd have choice.  Distros have to follow
what upstream does, even if it breaks something else (or they could
revert the "P" patch and get an entirely specular set of bug reports).

>> > The solution could be to extend binfmt_misc so that it sets two
>> > environment variables BINFMT_MISC_PID and BINFMT_MISC_ORIG_ARGV0.  The
>> > former is set to the pid of the binfmt "interpreter" program, the latter
>> > to the argv[0] value.  Then QEMU can check if BINFMT_MISC_PID matches
>> > getpid() and, if so, trust the BINFMT_MISC_ORIG_ARGV0 value.
> Certainly if we're in a position to get the kernel to be more
> informative about how it invoked us that would be the ideal.

I think it's simply that "P" was ill-designed (possibly because
implementing the above is not trivial).

Paolo