libc: Teach libc about the BTI elf note
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Authored by andrew on Oct 16 2023, 4:08 PM.

Details

Reviewers

markj
emaste

Group Reviewers

arm64

Commits

rGd4163257401c: rtld: Teach rtld about the BTI elf note
rGfd5aaf2ea017: libc: Teach libc about the BTI elf note
rG5270cc9757fb: rtld: Teach rtld about the BTI elf note

Summary

Add the Branch Target Identification (BTI) note to libc assembly
sources. As all obect files need the note for the library to have it
we need to insert it in all asm files.

Diff Detail

Repository

rG FreeBSD src repository

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Lint Not Applicable

Unit

Tests Not Applicable

Event Timeline

andrew created this revision.Oct 16 2023, 4:08 PM

Herald added subscribers: emaste, imp. · View Herald TranscriptOct 16 2023, 4:08 PM

andrew requested review of this revision.Oct 16 2023, 4:08 PM

andrew added a parent revision: D42227: csu: Teach libc about PAC and BTI.

andrew added a child revision: D42229: rtld: Teach rtld about the BTI elf note.

Harbormaster completed remote builds in B54007: Diff 128838.Oct 16 2023, 4:08 PM

Can we have some simple regression test which compiles and links a sample program with combinations of PAC and BTI enabled and disabled, and then verifies that libc and rtld don't silently cause features to be disabled? I'm worried that this will be a maintenance burden as new MI asm files are added.

There is a flag for lld that will cause it to fail to link when the note is missing BTI support. I've been using it to find all assembly files missing the note.

In D42228#964222, @andrew wrote:

There is a flag for lld that will cause it to fail to link when the note is missing BTI support. I've been using it to find all assembly files missing the note.

It would be nice if there was a way for the compiler to insert/update the note, rather than having to manually annotate every single assembly file...

This revision is now accepted and ready to land.Oct 23 2023, 2:04 PM

emaste accepted this revision.Oct 23 2023, 5:07 PM

Closed by commit rG5270cc9757fb: rtld: Teach rtld about the BTI elf note (authored by andrew). · Explain WhyOct 30 2023, 5:56 PM

This revision was automatically updated to reflect the committed changes.

andrew added a commit: rG5270cc9757fb: rtld: Teach rtld about the BTI elf note.

Herald added a subscriber: bdragon. · View Herald TranscriptOct 30 2023, 5:56 PM

andrew added a commit: rGfd5aaf2ea017: libc: Teach libc about the BTI elf note.Nov 21 2023, 11:18 AM

andrew added a commit: rGd4163257401c: rtld: Teach rtld about the BTI elf note.Feb 19 2024, 4:47 PM