Allow ddb and dtrace use the DMAP region on arm64
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Authored by andrew on Sep 21 2021, 5:37 PM.

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Reviewers

mhorne
manu

Group Reviewers

arm64

Commits

rG7b7f391db4f0: Allow ddb and dtrace use the DMAP region on arm64
rG3d2533f5c29f: Allow ddb and dtrace use the DMAP region on arm64

Summary

When writing to memory on arm64 we may be trying to be accessing a
read-only page. In this case try to access via the DMAP region to
get a writable location.

While here simplify writing data in DDB and stop trashing the size as
it is passed into the cache handling functions.

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Repository

rG FreeBSD src repository

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Tests Not Applicable

Event Timeline

andrew created this revision.Sep 21 2021, 5:37 PM

Herald added a reviewer: manu. · View Herald TranscriptSep 21 2021, 5:37 PM

Herald added subscribers: emaste, imp. · View Herald Transcript

andrew requested review of this revision.Sep 21 2021, 5:37 PM

Harbormaster completed remote builds in B41627: Diff 95470.Sep 21 2021, 5:37 PM

andrew mentioned this in D32026: Add pmap_change_prot on arm64.Sep 21 2021, 5:38 PM

Why should the DMAP alias be writable? Its protections are supposed to be kept in sync with the corresponding KVA page. You add a comment to this effect in D32026, but I think pmap_change_props_locked() is still missing the code that actually updates the DMAP protections (at least I don't see it).

Split out the translate code inot a new function
Add dtrace support

Harbormaster completed remote builds in B41666: Diff 95560.Sep 23 2021, 12:53 PM

andrew retitled this revision from Allow ddb to write via the DMAP region on arm64 to Allow ddb and dtrace use the DMAP region on arm64.Sep 23 2021, 12:54 PM

andrew edited the summary of this revision. (Show Details)

In D32053#723298, @mhorne wrote:

Why should the DMAP alias be writable? Its protections are supposed to be kept in sync with the corresponding KVA page. You add a comment to this effect in D32026, but I think pmap_change_props_locked() is still missing the code that actually updates the DMAP protections (at least I don't see it).

In the current version of that change I forced the DMAP to be writable. I expect to change it to match the comment when I have time to update arm64_get_writable_addr to map the memory as writable.

This revision was not accepted when it landed; it landed in state Needs Review.Oct 1 2021, 10:28 AM

Closed by commit rG3d2533f5c29f: Allow ddb and dtrace use the DMAP region on arm64 (authored by andrew). · Explain Why

This revision was automatically updated to reflect the committed changes.

andrew added a commit: rG3d2533f5c29f: Allow ddb and dtrace use the DMAP region on arm64.

andrew added a commit: rG7b7f391db4f0: Allow ddb and dtrace use the DMAP region on arm64.Jan 4 2022, 10:51 AM