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

[Alexander Graf <agraf@suse.de>]

On 25.08.14 11:09, Riku Voipio wrote:
> Hi,
> 
> After weekend, I think the solution to using the P flag is to
> go back to Joakim's original patch:
> 
> http://lists.gnu.org/archive/html/qemu-devel/2014-07/msg02269.html
> 
> With this, we get:
> 
> If you continue to use qemu-x-static in your binfmt_misc registration,
> nothing changes - both old and new qemu work using the old binfmt
> registration.
> 
> If you rename the binary qemu-x-binfmt, you need to update the
> binfmt_misc register to have P flag and new binary  - you get correct
> argv with new qemu. Any old qemu you still have around, will stop
> working. But with "file not found" error rather than obscurely eating
> one of the arguments and running regardless.
> 
> This leaves us with one case - people who are used to running
> qemu-x-static ./binary to test single binaries. Distro's will need
> leave a symlink from qemu-x-binfmt qemu-x-static. The "-binfmt" string
> check doesn't trigger, and qemu works as before.
> 
> The key point: this way nobody's working setup will break, unless they
> update binfmt registration. As long as the change is done by users
> them self (I need correct argv0 -> I will update binfmt), there is very
> little surprise for anyone. 
> 
> There will be some fallout once *distributions* change the binfmt - users
> will notice their existing qemu chroots stop working with a "file not
> found" error for any binary they try to run.
> 
> If we find even this breakage too much, I'm not sure this can be fixed.

I would very much prefer if we could stick with only a single binary.
And yes, switching semantics when you use binfmt wrappers will hurt for
a short while, but after that everyone will have their setups changed
and we're safe for the future.


Alex