Add support for CFI based stack walking on Arm64.

Add support for CFI based stack walking on Arm64.

This CL adds CFI based stack walking support for Arm64 to BreakPad along with
unit tests.  The Arm64 CFI stack walker is based on the Arm CFI stack walker

BUG=367367,335641,354405
R=blundell@chromium.org, mark@chromium.org

Committed: 1325

[rmcilroy]

Mark, please take a look.  Blundell, I've added you in case there are any iOS
issues I've introduced with this change.  Thanks.

[Mark Mentovai]

LGTM. Colin, will this impact ARM64 iOS stackwalks at all?

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.cc
File processor/stackwalker_arm64.cc (right):

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.c...
processor/stackwalker_arm64.cc:93: for (int i = 0; register_names[i]; i++)
Brace this, it’s controlling something that’s longer than a line.

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.c...
processor/stackwalker_arm64.cc:100: &caller_registers))
Let’s get some braces here. Since the condition is taking up more than a line,
the braces help you see that “return NULL” is what’s guarded by the “if”.

[rmcilroy]

Thanks Mark.  Colin, should this be OK for iOS too?

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.cc
File processor/stackwalker_arm64.cc (right):

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.c...
processor/stackwalker_arm64.cc:93: for (int i = 0; register_names[i]; i++)
On 2014/04/30 16:31:33, Mark Mentovai wrote:
> Brace this, it’s controlling something that’s longer than a line.

Done.

https://breakpad.appspot.com/1664002/diff/20002/processor/stackwalker_arm64.c...
processor/stackwalker_arm64.cc:100: &caller_registers))
On 2014/04/30 16:31:33, Mark Mentovai wrote:
> Let’s get some braces here. Since the condition is taking up more than a line,
> the braces help you see that “return NULL” is what’s guarded by the “if”.

Done.

[blundell]

LGTM from the iOS side. There is no CFI given on iOS, so the conditional at line
240 of stackwalker_arm64.cc will fail and the flow will move immediately into
GetCallerByFramePointer() as desired.

[rmcilroy]

On 2014/05/05 07:49:47, blundell wrote:
> LGTM from the iOS side. There is no CFI given on iOS, so the conditional at
line
> 240 of stackwalker_arm64.cc will fail and the flow will move immediately into
> GetCallerByFramePointer() as desired.

Thanks Colin.  Landing now and then will roll to Chromium.

[rmcilroy]

Committed patchset #3 manually as r1325 (presubmit successful).