Add a new unwind method on error.

If a function crashes by jumping into unexecutable code, the old method
could not unwind through that. Add a fallback method to set the pc from
the default return address location.

In addition, add a new finished check for steps. This will provide a method
to indicate that this step is the last step. This prevents cases where
the fallback method might be triggered incorrectly.

Update the libbacktrace code to unwind using the new methodology.

Update the unwind tool to use the new unwind methodology.

Add a new option to crasher that calls through a null function.

Create a new object, Unwinder, that encapsulates the a basic unwind. For now,
libbacktrace will still use the custom code.

Added new unit tests to cover the new cases. Also add a test that
crashes calling a nullptr as a function, and then has call frames in
the signal stack.

Bug: 65842173

Test: Pass all unit tests, verify crasher dumps properly.
Change-Id: Ia18430ab107e9f7bdf0e14a9b74710b1280bd7f4

1 files changed, 1 insertions, 0 deletions

diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index e1957ca40..ca055161d 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -61,6 +61,7 @@ cc_library {
         "Maps.cpp",
         "Memory.cpp",
         "Regs.cpp",
+        "Unwinder.cpp",
         "Symbols.cpp",
     ],