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Differential D42530

kern linker: Do not try to unload kernel
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Authored by zlei on Nov 9 2023, 3:43 PM.
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guest-patmaddox
imp
jhb
olce

Details

Reviewers
kib
dfr
dab
cem
jhb
Commits
rGa7b2c455505a: kern linker: Do not touch userrefs of the kernel file
rG7da45efb0921: kern linker: Do not touch userrefs of the kernel file
rG39450eba8e6c: kern linker: Do not touch userrefs of the kernel file
Summary

The userland or kernel shall not unload the kernel module.

MFC after: 2 weeks

Test Plan
# kldstat 
Id Refs Address                Size Name
 1    1 0xffffffff80200000  1d35008 kernel
# kldunload kernel
kldunload: can't unload file: Device busy

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rG FreeBSD src repository
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Event Timeline

zlei created this revision.Nov 9 2023, 3:43 PM
Herald added a subscriber: imp. · View Herald TranscriptNov 9 2023, 3:43 PM
zlei requested review of this revision.Nov 9 2023, 3:43 PM
dfr accepted this revision.Nov 9 2023, 3:44 PM

Looks good

This revision is now accepted and ready to land.Nov 9 2023, 3:44 PM
dab accepted this revision.Nov 10 2023, 2:07 AM
zlei added a reviewer: cem.Nov 10 2023, 9:25 AM
zlei added a comment.Nov 10 2023, 9:32 AM

I was about to commit this I found that prior to d9ce8a41eac9 (kern_linker: Handle module-loading failures in preloaded .ko files) the kernel can not be unloaded.

CC the author @cem for this. See also discuss at ML https://lists.freebsd.org/archives/freebsd-current/2023-November/004950.html .

So this is more a regression than a feature.

zlei added a comment.Nov 10 2023, 7:17 PM

I tested FreeBSD-11.4-RELEASE-amd64-bootonly.iso which does not have d9ce8a41eac9 ,:

# kldunload kernel
kldunload: can't unload file: Device busy

There is also log kldunload: attempt to unload file that was loaded by the kernel from dmesg.

So I can conclude d9ce8a41eac9 introduced regression.

jhb accepted this revision.Nov 15 2023, 4:10 PM
jhb added a subscriber: jhb.

Yes, this is a regression from d9ce8a41eac9 and I think this is the right way to fix it.

sys/kern/kern_linker.c
1798–1799

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guest-patmaddox added a subscriber: guest-patmaddox.Dec 13 2023, 9:59 PM
Closed by commit rG39450eba8e6c: kern linker: Do not touch userrefs of the kernel file (authored by zlei). · Explain WhyMar 26 2024, 8:48 AM
This revision was automatically updated to reflect the committed changes.
zlei added a commit: rG39450eba8e6c: kern linker: Do not touch userrefs of the kernel file.
Herald added a subscriber: olce. · View Herald TranscriptMar 26 2024, 8:48 AM
zlei added a commit: rG7da45efb0921: kern linker: Do not touch userrefs of the kernel file.Apr 9 2024, 4:11 AM
zlei added a commit: rGa7b2c455505a: kern linker: Do not touch userrefs of the kernel file.Apr 9 2024, 4:14 AM

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sys/
kern/
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sys/kern/kern_linker.c

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