csu: Teach libc about PAC and BTI
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Authored by andrew on Oct 16 2023, 4:08 PM.

Details

Reviewers

markj

Group Reviewers

arm64

Commits

rGeb1dae1c40f2: csu: Teach csu about PAC and BTI
rG522126fea724: csu: Teach csu about PAC and BTI

Summary

Add the Branch Target Identification (BTI) note to libc assembly
sources and Pointer Authentication Code (PAC) instructions to _init and
_fini.

_init and _fini may be called indirectly so need a BTI landing pad. As
they are non-leaf functions use the appropriate PAC instruction that
also guardes against changing the link register.

As all obect files need the note for any binary using these object files
we need to insert it in all asm files.

Diff Detail

Repository

rG FreeBSD src repository

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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: D42226: arm64: Add PAC instruction macros.

andrew added a child revision: D42228: libc: Teach libc about the BTI elf note.

Harbormaster completed remote builds in B54006: Diff 128837.Oct 16 2023, 4:08 PM

markj added inline comments.Oct 17 2023, 1:48 PM

lib/csu/aarch64/crti.S
31	Missing a newline after the include.
lib/csu/common/crtbrand.S
53	Why add it to this file?
lib/csu/common/ignore_init_note.S
47	Why is this needed here?

markj added inline comments.Oct 17 2023, 1:49 PM

lib/csu/common/crtbrand.S
53	I missed this in the description: As all obect files need the note for any binary using these object files we need to insert it in all asm files.

Add missing newline
Add a comment why GNU_PROPERTY_AARCH64_FEATURE_1_NOTE is needed in common files

Harbormaster completed remote builds in B54126: Diff 129229.Oct 23 2023, 8:50 AM

markj accepted this revision.Oct 23 2023, 1:57 PM

This revision is now accepted and ready to land.Oct 23 2023, 1:57 PM

emaste added inline comments.Oct 23 2023, 5:06 PM

lib/csu/common/feature_note.S
44–47	It's kind of annoying to need `#ifdef __aarch64__` in each of these files, although I think it's going to be awkward however we do it. Is there a clean way we could do it with a common definition?

andrew added inline comments.Oct 23 2023, 5:38 PM

lib/csu/common/feature_note.S
44–47	At the moment I'm placing it per-file to ensure all files have been checked. There is a flag for lld that will fail to link when the note is missing so I can use that to find missing files. The only place I know that is still missing the note is zfs. When that is fixed we could enable the lld flag (after checking ports aren't affected).