imgact_binmisc: Optionally pre-open the interpreter vnode
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Authored by dfr on Nov 18 2022, 3:11 PM.

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rG461210143fbb: imgact_binmisc: Optionally pre-open the interpreter vnode
rG5eeb4f737f11: imgact_binmisc: Optionally pre-open the interpreter vnode

Summary

This allows the use of chroot and/or jail environments which depend on
interpreters registed with imgact_binmisc.

Test Plan

Ad-hoc testing of arm64 chroot environments with qemu-user-static

Diff Detail

Repository

rG FreeBSD src repository

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Event Timeline

dfr requested review of this revision.Nov 18 2022, 3:11 PM

dfr created this revision.

Harbormaster completed remote builds in B48415: Diff 113264.Nov 18 2022, 3:11 PM

I added a new field to struct image_args. Since this was added to the end of the structure, it should make it possible to MFC to stable/13 since the structure is owned and zeroed by do_execve and any imgact modules should not be affected.

Rebased

Harbormaster completed remote builds in B48639: Diff 113902.Dec 7 2022, 2:00 PM

I'm not 100% sure about the vnode protocols are right, but they seem fine.
Not sure if I reinstall qemu and its implications, but that aught to be documented if it doesn't just work.

sys/kern/imgact_binmisc.c
69	Having this in the middle is OK, right? I believe so, since this is in the .c file so no other files can reference it...
179	What happens if I reinstall qemu?
sys/sys/imgact.h
97	This is good.

This revision is now accepted and ready to land.Dec 7 2022, 11:57 PM

Thanks for the review. I will follow up with a PR for qemu-bsd-user to remove the logic which adds the emulator binary to emulated execve calls and make a separate review for the qemu-user-static-devel port to enable pre-open and also remind users to 'service qemu_user_static restart' or something similar after an upgrade.

sys/kern/imgact_binmisc.c
69	Yes - nothing outside this file can depend on the layout of imgact_binmisc_entry
179	The kernel will continue to use the old qemu until binmiscctl refreshes the mapping.