Le 14/07/2019 à 18:19, John Paul Adrian Glaubitz a écrit : > Hi! > >> On Jul 14, 2019, at 3:40 PM, Laurent Vivier <laur...@vivier.eu> wrote: >> >> Add --preserve-arg0 in qemu-binfmt-conf.sh to configure the preserve-arg0 >> flag. >> >> Now, if QEMU is started with -0 or QEMU_ARGV0 and an empty parameter >> argv[0] (the full pathname provided by binfmt-misc) is removed and >> replaced by argv[1] (the original argv[0] provided by binfmt-misc when >> 'P'/preserve-arg[0] is set) >> >> For instance: >> >> $ sudo QEMU_ARGV0= chroot m68k-chroot sh -c 'echo $0' >> sh >> >> without this patch: >> >> $ sudo chroot m68k-chroot sh -c 'echo $0' >> /usr/bin/sh > > As a regular user of qemu-user (we’re using qemu-user to run Debian’s buildds > for m68k and sh4), I would like to add that the idea of having to pass > additional environment variables to make qemu behave as expected, i.e. as the > real hardware, is sub-optimal. > > I would prefer that enabling the preserve flag with the qemu-binfmt.sh script > would make qemu-user behave correctly.
QEMU is not able to detect if it has been started by binfmt_misc with the preserve-arg[0] enabled or not, so it can't adapt the args analysis to get the correct list. > > If I understand correctly, the current design with the environment variable > was chosen because my preferred approach would break compatibility in certain > cases. However, I think that correct emulation is more important than > compatibility to an old broken behavior and I would therefore be in favor to > make the correct behavior default. > > This will also be necessary when using qemu-user with Debian’s sbuild to > “cross”-build packages with qemu-user. This particular bug was actually > discovered while building Debian packages for m68k and sh4 using qemu-user. The problem we have here is we don't know how qemu-user is used in the wild. In my knowledge you are the most involved user, but you're not the only one reporting problem via launchpad. Moreover, distros provide qemu-user statically linked and binfmt configuration files, so we can guess we have other users. And I don't like to break existing things... What I can propose: 1- modify this patch to add a configure option: by default qemu will need the QEMU_ARGV0 but we will be able to define at configure time it always runs with preserve-arg[0] flag enabled (something like "--enable-preserve-arg0") [So debian will be able to provide qemu-user-static with this enabled by default if you're not afraid to break debian users environment] 2- try (again) to push in the kernel the binfmt_misc namespace that allows to have per chroot basis binfmt configuration 3- once 3 done, enable preserve-arg[0] by default Thanks, Laurent
