sys/tools: add -s options for KCFI use
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Authored by aokblast on Feb 23 2025, 5:54 PM.

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Reviewers

markj
brooks

Summary

The KCFI requires all function signature match.

For .m files in KCFI, it calls kobj_error_methods in default.

Which means the signature will mismatched thus the KCFI will emit trap
in kernel.

Thus we proposed a option -s for makeobjops.awk to generate the correct
signature for each missing default function.

We do not enable this feature by default because it may enlarge the
kernel size.

sys/kern: fix wrong indent

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rG FreeBSD src repository

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Buildable 62597
Build 59481: arc lint + arc unit

Event Timeline

aokblast created this revision.Feb 23 2025, 5:54 PM

Herald added subscribers: olce, imp. · View Herald TranscriptFeb 23 2025, 5:54 PM

aokblast requested review of this revision.Feb 23 2025, 5:54 PM

Harbormaster completed remote builds in B62597: Diff 151375.Feb 23 2025, 5:54 PM

aokblast added a child revision: D46193: sys: implement Kernel CFI from clang.Feb 23 2025, 6:46 PM

lwhsu added a subscriber: lwhsu.Feb 24 2025, 4:25 AM

aokblast added reviewers: markj, brooks.Feb 25 2025, 1:34 PM

We do not enable this feature by default because it may enlarge the kernel size.

How much larger is it in practice?

sys/tools/makeobjops.awk
302	How about `return kobj_error_method();`?

With opt_s:

    text      data       bss        dec         hex   filename
23241058   1754433   4537984   29533475   0x1c2a523   /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel

Without opt_s:

    text      data       bss        dec         hex   filename
23232582   1754433   4537984   29524999   0x1c28407   /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel

About 1k in text, not too much. But I think it is a useless size as it change nothings more than the signature.

sys/tools/makeobjops.awk
302	Calling kboj_error_method will incease the call stack. I don't know if it is a good implementation considering in kernel and the .m's frequently call. I don't have too much experience about it. If you think it is ok, I can do the corresponding change.