On Wed, 2024-10-02 at 16:08 +0200, Laurent Vivier wrote: > Le 02/10/2024 à 10:08, Ilya Leoshkevich a écrit : > > On Fri, 2024-08-30 at 15:36 -0700, Noah Goldstein wrote: > > > The new option '-qemu-children' makes it so that on `execve` the > > > child > > > process will be launch by the same `qemu` executable that is > > > currently > > > running along with its current commandline arguments. > > > > > > The motivation for the change is to make it so that plugins > > > running > > > through `qemu` can continue to run on children. Why not just > > > `binfmt`?: Plugins can be desirable regardless of > > > system/architecture > > > emulation, and can sometimes be useful for elf files that can run > > > natively. Enabling `binfmt` for all natively runnable elf files > > > may > > > not be desirable. > > > > Another reason to have this is that one may not have root > > permissions > > to configure binfmt-misc. > > A little note on that: binfmt_misc is now part of the user namespace > (since linux v6.7), so you can > configure binfmt_misc as a non root user in a given namepace. > > There is helper to use it with unshare from util-linux, you can do > things like that: > > With 'F' flag, load the interpreter from the initial namespace: > > $ /bin/qemu-m68k-static --version > qemu-m68k version 8.2.2 (qemu-8.2.2-1.fc40) > Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project > developers > $ unshare --map-root-user --fork --pid > --load-interp=":qemu- > m68k:M::\\x7fELF\\x01\\x02\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x > 00\\x00\\x00\\x02\\x00\\x04:\\xff\\xff\\xff\\xff\\xff\\xff\\xfe\\x00\ > \xff\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\xfe\\xff\\xff:/bin/qemu > -m68k-static:OCF" > --root=chroot/m68k/sid > # QEMU_VERSION= ls > qemu-m68k version 8.2.2 (qemu-8.2.2-1.fc40) > Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project > developers > # /qemu-m68k --version > qemu-m68k version 8.0.50 (v8.0.0-340-gb1cff5e2da95) > Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project > developers > > Without 'F' flag, from inside the namespace: > > $ unshare --map-root-user --fork --pid > --load-interp=":qemu- > m68k:M::\\x7fELF\\x01\\x02\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x > 00\\x00\\x00\\x02\\x00\\x04:\\xff\\xff\\xff\\xff\\xff\\xff\\xfe\\x00\ > \xff\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\xff\\xfe\\xff\\xff:/qemu- > m68k:OC" > --root=chroot/m68k/sid > # QEMU_VERSION= ls > qemu-m68k version 8.0.50 (v8.0.0-340-gb1cff5e2da95) > Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project > developers > # /qemu-m68k --version > qemu-m68k version 8.0.50 (v8.0.0-340-gb1cff5e2da95) > Copyright (c) 2003-2022 Fabrice Bellard and the QEMU Project > developers > > Thanks, > Laurent >
Thanks for posting this, I wasn't aware of this feature and it looks really useful. IIUC it also resolves the main problem this patch is dealing with: Enabling `binfmt` for all natively runnable elf files may not be desirable.
