Correct an obscure PV entry leak in the recent change to amd64's pmap_enter()
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Authored by alc on Jul 4 2018, 7:07 PM.

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rS335971: As of r335784, if pmap_enter() replaces a managed mapping by an unmanaged

Summary

Hypothetically, pmap_enter() could replace a managed mapping by an unmanaged mapping, in which case, pmap_enter() would currently leak the unlinked PV entry. This change frees that PV entry when the new mapping is unmanaged.

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rS FreeBSD src repository - subversion

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alc created this revision.Jul 4 2018, 7:07 PM

I noticed this bug while reading the i386 pmap code. :)

This revision is now accepted and ready to land.Jul 4 2018, 7:30 PM

kib accepted this revision.Jul 4 2018, 8:05 PM

Closed by commit rS335971: As of r335784, if pmap_enter() replaces a managed mapping by an unmanaged (authored by alc). · Explain WhyJul 5 2018, 2:04 AM

This revision was automatically updated to reflect the committed changes.

Herald added a subscriber: imp. · View Herald TranscriptJul 5 2018, 2:04 AM

In D16130#342002, @markj wrote:

I noticed this bug while reading the i386 pmap code. :)

I'm working on the i386 version. As you may have noticed, the i386 pmap has the CoW problem, but not the PV entry allocation problem.

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head/

sys/

amd64/

pmap.c

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Diff 44884

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head/sys/amd64/amd64/pmap.c

Correct an obscure PV entry leak in the recent change to amd64's pmap_enter()ClosedPublicActions