Stack sampling profiler: fix leaf function unwinding and remove blacklisting

Stack sampling profiler: fix leaf function unwinding and remove blacklisting

The leaf function unwinding has a bug where the new instruction pointer
is set to the stack pointer rather than the value at the stack
pointer. This causes the module check on the next iteration to fail,
resulting in stacks truncated at depth 1. This change fixes that bug.

The change also removes the associated leaf function blacklisting
implementation. This implementation is no longer needed as the third
party code that precipitated it is now detected by the valid module
check.

BUG=555770
Committed: https://crrev.com/eb8d42df5fbfb95ad409dfd2353d04674624c2f5
Cr-Commit-Position: refs/heads/master@{#363725}

[Mike Wittman, 2015-12-08 00:56:16]

wittman@chromium.org changed reviewers:
+ brucedawson@chromium.org

[Mike Wittman, 2015-12-08 00:56:17]

Hi Bruce, please take a look.

I'm about 80% confident this will work since the implementation satisfies all
known crash scenarios, mainly thanks to the module check. But it's possible we
could run into something unexpected.

If that happens worst case scenario would be that it crashes, we get some useful
crash data, revert, and come back with a simpler detection mechanism than the
leaf unwind blacklist.

[brucedawson, 2015-12-08 01:25:32]

I wonder whether this would be better as two changes rather than one, but no
matter. lgtm

[Mike Wittman, 2015-12-08 02:28:27]

On 2015/12/08 01:25:32, brucedawson wrote:
> I wonder whether this would be better as two changes rather than one, but no
> matter. lgtm

Normally I'd say so, but the blacklisting was never tested in the wild (due to
the bug) and very likely is no longer needed, so this approach seemed to be
cleaner with about the same amount of risk.

[Mike Wittman, 2015-12-08 02:50:40]

The CQ bit was checked by wittman@chromium.org

[commit-bot: I haz the power, 2015-12-08 02:51:42]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1503273003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1503273003/1

[commit-bot: I haz the power, 2015-12-08 03:55:32]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-12-08 03:56:05]

Description was changed from

==========
Stack sampling profiler: fix leaf function unwinding and remove blacklisting

The leaf function unwinding has a bug where the new instruction pointer
is set to the stack pointer rather than the value at the stack
pointer. This causes the module check on the next iteration to fail,
resulting in stacks truncated at depth 1. This change fixes that bug.

The change also removes the associated leaf function blacklisting
implementation. This implementation is no longer needed as the third
party code that precipitated it is now detected by the valid module
check.

BUG=555770
==========

to

==========
Stack sampling profiler: fix leaf function unwinding and remove blacklisting

The leaf function unwinding has a bug where the new instruction pointer
is set to the stack pointer rather than the value at the stack
pointer. This causes the module check on the next iteration to fail,
resulting in stacks truncated at depth 1. This change fixes that bug.

The change also removes the associated leaf function blacklisting
implementation. This implementation is no longer needed as the third
party code that precipitated it is now detected by the valid module
check.

BUG=555770

Committed: https://crrev.com/eb8d42df5fbfb95ad409dfd2353d04674624c2f5
Cr-Commit-Position: refs/heads/master@{#363725}
==========

[commit-bot: I haz the power, 2015-12-08 03:56:05]

Patchset 1 (id:??) landed as
https://crrev.com/eb8d42df5fbfb95ad409dfd2353d04674624c2f5
Cr-Commit-Position: refs/heads/master@{#363725}