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

1 files changed, 24 insertions, 4 deletions

diff --git a/lldb/source/Plugins/Process/Linux/NativeThreadLinux.h b/lldb/source/Plugins/Process/Linux/NativeThreadLinux.h
index bf6b00a..f1b6a6e 100644
--- a/lldb/source/Plugins/Process/Linux/NativeThreadLinux.h
+++ b/lldb/source/Plugins/Process/Linux/NativeThreadLinux.h
@@ -13,6 +13,8 @@
 #include "lldb/lldb-private-forward.h"
 #include "lldb/Host/common/NativeThreadProtocol.h"
 
+#include <sched.h>
+
 #include <map>
 #include <memory>
 #include <string>
@@ -54,11 +56,16 @@ namespace process_linux {
         // ---------------------------------------------------------------------
         // Interface for friend classes
         // ---------------------------------------------------------------------
-        void
-        SetRunning ();
 
-        void
-        SetStepping ();
+        /// Resumes the thread.  If @p signo is anything but
+        /// LLDB_INVALID_SIGNAL_NUMBER, deliver that signal to the thread.
+        Error
+        Resume(uint32_t signo);
+
+        /// Single steps the thread.  If @p signo is anything but
+        /// LLDB_INVALID_SIGNAL_NUMBER, deliver that signal to the thread.
+        Error
+        SingleStep(uint32_t signo);
 
         void
         SetStoppedBySignal(uint32_t signo, const siginfo_t *info = nullptr);
@@ -102,6 +109,18 @@ namespace process_linux {
         void
         MaybeLogStateChange (lldb::StateType new_state);
 
+        NativeProcessLinux &
+        GetProcess();
+
+        void
+        SetStopped();
+
+        inline void
+        MaybePrepareSingleStepWorkaround();
+
+        inline void
+        MaybeCleanupSingleStepWorkaround();
+
         // ---------------------------------------------------------------------
         // Member Variables
         // ---------------------------------------------------------------------
@@ -111,6 +130,7 @@ namespace process_linux {
         std::string m_stop_description;
         using WatchpointIndexMap = std::map<lldb::addr_t, uint32_t>;
         WatchpointIndexMap m_watchpoint_index_map;
+        cpu_set_t m_original_cpu_set; // For single-step workaround.
     };
 
     typedef std::shared_ptr<NativeThreadLinux> NativeThreadLinuxSP;