CHERI: add mem{cpy,move}_data
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Authored by brooks on Fri, Jun 19, 2:12 PM.

Details

Reviewers

kib
markj
jhb
jrtc27

Group Reviewers

cheri

Summary

Add kernel-only provenance-discarding memcpy_data and
memmove_data APIs intended to copy raw data which does not contain
pointers (e.g., buffers on their way to or from network or storage
devices). On CHERI architectures, they will explicitly remove tags
from capabilities, removing any provenance. This reduces the risk of
accidental spread of pointers on CHERI system.

This includes a simple C implementation for CHERI targets.

Effort: CHERI upstreaming
Sponsored by: DARPA, AFRL, Innovate UK

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Passed

Unit

No Test Coverage

Build Status

Buildable 74061
Build 70944: arc lint + arc unit

Event Timeline

brooks created this revision.Fri, Jun 19, 2:12 PM

Herald added subscribers: ziaee, imp. · View Herald TranscriptFri, Jun 19, 2:12 PM

brooks requested review of this revision.Fri, Jun 19, 2:12 PM

Harbormaster completed remote builds in B73997: Diff 180057.Fri, Jun 19, 2:12 PM

Herald added a reviewer: cheri. · View Herald TranscriptFri, Jun 19, 2:12 PM

Herald added a reviewer: cheri. · View Herald Transcript

brooks added a parent revision: D57661: Add kernel manpages for bcopy, memcpy, and memmove.Fri, Jun 19, 2:12 PM

brooks added a child revision: D57663: CHERI: declare copy{in,out}ptr and copyoutptr_nofault.

ziaee added inline comments.Fri, Jun 19, 3:35 PM

share/man/man9/memcpy.9
91	typo

Fix typo

Harbormaster completed remote builds in B74011: Diff 180075.Fri, Jun 19, 5:23 PM

brooks marked an inline comment as done.Fri, Jun 19, 5:23 PM

emaste added a subscriber: emaste.Fri, Jun 19, 5:24 PM

emaste added inline comments.

sys/sys/systm.h
295	How widely used is bcopy_data in CHERI? Is it reasonable to move those to memmove_data (possibly moving to memmove first in FreeBSD)? It seems slightly unfortunate to make a new version of a legacy/obsolete interface.

brooks added inline comments.Fri, Jun 19, 5:40 PM

sys/sys/systm.h
295	None of these are widely used. memmove_data is currently completely unused except to implement bcopy_data. I actually think most (or even all) could be memcpy_data (I don't think any of these overlap). The one slightly perverse argument for bcopy_data is that it's safely outside the reserved mem* namespace.