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Work around a stepping bug in arm64 android M
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Authored by labath on Feb 22 2016, 8:23 AM.

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Summary

On arm64, linux<=4.4 and Android<=M there is a bug, which prevents single-stepping from working when
the system comes back from suspend, because of incorrectly initialized CPUs. This did not really
affect Android<M, because it did not use software suspend, but it is a problem for M, which uses
suspend (doze) quite extensively. Fortunately, it seems that the first CPU is not affected by
this bug, so this commit implements a workaround by forcing the inferior to execute on the first
cpu whenever we are doing single stepping.

While inside, I have moved the implementations of Resume() and SingleStep() to the thread class
(instead of process).

Diff Detail

Repository
rL LLVM

Event Timeline

labath updated this revision to Diff 48689.Feb 22 2016, 8:23 AM
labath retitled this revision from to Work around a stepping bug in arm64 android M.
labath updated this object.
labath added reviewers: tberghammer, ovyalov.
labath added a subscriber: lldb-commits.
labath updated this revision to Diff 48690.Feb 22 2016, 8:29 AM

Avoid an unused function warning on non-arm64 arches.

ovyalov accepted this revision.Feb 22 2016, 10:45 AM
ovyalov edited edge metadata.
ovyalov added inline comments.
source/Plugins/Process/Linux/NativeThreadLinux.cpp
250 ↗(On Diff #48690)

Could you use Error error(errno, eErrorTypePOSIX) instead of strerror here?

source/Plugins/Process/Linux/SingleStepCheck.cpp
79 ↗(On Diff #48690)

Kill child before return?

source/Plugins/Process/Linux/SingleStepCheck.h
41 ↗(On Diff #48690)

s/liblldb_NativeThreadLinux_H_/liblldb_SingleStepCheck_H_

This revision is now accepted and ready to land.Feb 22 2016, 10:45 AM
This revision was automatically updated to reflect the committed changes.
labath marked 2 inline comments as done.