Work around a stepping bug in arm64 android M
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).
Reviewers: tberghammer, ovyalov
Subscribers: aemerson, rengolin, tberghammer, danalbert, srhines, lldb-commits
Differential Revision: http://reviews.llvm.org/D17509
llvm-svn: 261636
diff --git a/lldb/source/Plugins/Process/Linux/SingleStepCheck.h b/lldb/source/Plugins/Process/Linux/SingleStepCheck.h
new file mode 100644
index 0000000..f83f7c9
--- /dev/null
+++ b/lldb/source/Plugins/Process/Linux/SingleStepCheck.h
@@ -0,0 +1,41 @@
+//===-- SingleStepCheck.h ------------------------------------- -*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef liblldb_SingleStepCheck_H_
+#define liblldb_SingleStepCheck_H_
+
+namespace lldb_private
+{
+namespace process_linux
+{
+
+namespace impl
+{
+extern bool
+SingleStepWorkaroundNeeded();
+}
+
+// arm64 linux had a bug which prevented single-stepping and watchpoints from working on non-boot
+// cpus, due to them being incorrectly initialized after coming out of suspend. This issue is
+// particularly affecting android M, which uses suspend ("doze mode") quite aggressively. This
+// code detects that situation and makes single-stepping work by doing all the step operations on
+// the boot cpu.
+//
+// The underlying issue has been fixed in android N and linux 4.4. This code can be removed once
+// these systems become obsolete.
+inline bool
+SingleStepWorkaroundNeeded()
+{
+ static bool value = impl::SingleStepWorkaroundNeeded();
+ return value;
+}
+} // end namespace process_linux
+} // end namespace lldb_private
+
+#endif // #ifndef liblldb_SingleStepCheck_H_