Differential D41634

arm64 pmap: allocate leaf page table page for wired userspace superpages
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Authored by bnovkov on Aug 29 2023, 2:24 PM.

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markj
andrew
manu
kib
alc

Commits

rGab6bc4893e4d: arm64: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping
rG808f5ac3c6dc: arm64: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping

Summary

This patch fixes a syzkaller issue regarding wired userspace superpages by allocating a leaf page table page for wired userspace superpages.

The original issue is an edge case that creates an unmapped, wired region in userspace. Subsequent faults on this region can trigger wired superpage creation, leading to a panic upon demotion as the pmap does not create a leaf page table page for the wired superpage. D19670 fixed this by disallowing preemptive creation of wired superpage mappings, but that fix is currently interfering with an ongoing effort of speeding up vm_map_wire for large, contiguous entries.

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rG FreeBSD src repository

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Event Timeline

bnovkov created this revision.Aug 29 2023, 2:24 PM

Herald added a reviewer: andrew. · View Herald TranscriptAug 29 2023, 2:24 PM

Herald added a reviewer: andrew. · View Herald Transcript

Herald added a reviewer: manu. · View Herald Transcript

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

bnovkov requested review of this revision.Aug 29 2023, 2:24 PM

bnovkov added reviewers: kib, alc.Sep 16 2023, 4:45 PM

markj accepted this revision.Sep 17 2023, 11:23 AM

This revision is now accepted and ready to land.Sep 17 2023, 11:23 AM

alc accepted this revision.Sep 18 2023, 7:57 AM

alc added inline comments.

sys/arm64/arm64/pmap.c
4897	This was indented too far.

Closed by commit rG808f5ac3c6dc: arm64: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping (authored by bnovkov, committed by markj). · Explain WhyOct 9 2023, 12:48 AM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rG808f5ac3c6dc: arm64: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping.

markj added a commit: rGab6bc4893e4d: arm64: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping.Oct 24 2023, 1:38 PM

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sys/

arm64/

arm64/

29 lines

Diff 128428

sys/arm64/arm64/pmap.c

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