> Le 25 août 2014 à 14:46, Alexander Graf <ag...@suse.de> a écrit : > > > > > On 25.08.14 14:42, Riku Voipio wrote: > > On Mon, Aug 25, 2014 at 11:14:58AM +0200, Alexander Graf wrote: > >> > >> > >> 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. > > > > I don't really the unpredictable nature of the breakage. Take > > $ rm a b c > > > > With P flag: /bin/rm rm a b c > > Without P flag: /bin/rm a b c > > > > If we use old qemu with P flag: qemu will run /bin/rm with argv: "/bin/rm rm > > a b c" > > -> tries to delete "rm" > > If we use new qemu without P flag, qemu will run /bin/rm with argv: "a b c" > > -> fails to delete "a" > > > > This is the black magic errors that drive users nuts when they try to debug > > what > > is happening... "File not found" when the qemu binary is not in the > > right place is confusing enough. > > Yes, but is anyone actually using the "P" flag? We've never advertised > anywhere that QEMU supports it. > > Maybe we should just make the next version be 3.0 and declare it a major > ABI breakage ;).
You can also add the feature and let's the configure manages if it must be enabled or not. Regards, Laurent
