Change the way breakpoints work.
This replaces the breakpoint mechanism with a more efficient approach.
We now insert breakpoint instructions into the bytecode stream instead of
maintaining a table. This requires mapping DEX files as private instead
of shared, which allows copy-on-write to work. mprotect() is used to
guard the pages against inadvertent writes.
Unused opcode EC is now OP_BREAKPOINT. It's not recognized by dexdump or
any interpreter except portdbg, but it can be encountered by the bytecode
verifier (the debugger can request breakpoints in unverified code).
Breakpoint changes are blocked while the verifier runs to avoid races.
This eliminates method->debugBreakpointCount, which is no longer needed.
(Also, it clashed with LinearAlloc's read-only mode.)
The deferred verification error mechanism was using a code-copying
approach to modify the bytecode stream. That has been changed to use
the same copy-on-write modification mechanism.
Also, normalized all PAGE_SIZE/PAGESIZE references to a single
SYSTEM_PAGE_SIZE define.
Simple Fibonacci computation test times (opal-eng):
JIT, no debugger: 10.6ms
Fast interp, no debugger: 36ms
Portable interp, no debugger: 43.8ms
ORIG debug interp, no breakpoints set: 458ms
ORIG debug interp, breakpoint set nearby: 697ms
NEW debug interp, no breakpoints set: 341ms
NEW debug interp, breakpoints set nearby: 341ms
Where "nearby" means there's a breakpoint in the method doing the
computation that isn't actually hit -- the VM had an optimization where
it flagged methods with breakpoints and skipped some of the processing
when possible.
The bottom line is that code should run noticeably faster while a
debugger is attached.
diff --git a/vm/interp/Interp.h b/vm/interp/Interp.h
index cd4c7ec..015c3db 100644
--- a/vm/interp/Interp.h
+++ b/vm/interp/Interp.h
@@ -13,6 +13,7 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
+
/*
* Dalvik interpreter public definitions.
*/
@@ -34,12 +35,41 @@
void dvmThrowVerificationError(const Method* method, int kind, int ref);
/*
- * Breakpoint optimization table.
+ * One-time initialization and shutdown.
+ */
+bool dvmBreakpointStartup(void);
+void dvmBreakpointShutdown(void);
+
+/*
+ * Breakpoint implementation.
*/
void dvmInitBreakpoints();
-void dvmAddBreakAddr(Method* method, int instrOffset);
-void dvmClearBreakAddr(Method* method, int instrOffset);
+void dvmAddBreakAddr(Method* method, unsigned int instrOffset);
+void dvmClearBreakAddr(Method* method, unsigned int instrOffset);
bool dvmAddSingleStep(Thread* thread, int size, int depth);
void dvmClearSingleStep(Thread* thread);
+#ifdef WITH_DEBUGGER
+/*
+ * Recover the opcode that was replaced by a breakpoint.
+ */
+u1 dvmGetOriginalOpCode(const u2* addr);
+
+/*
+ * Temporarily "undo" any breakpoints set in a specific method. Used
+ * during verification.
+ *
+ * Locks the breakpoint set, and leaves it locked.
+ */
+void dvmUndoBreakpoints(Method* method);
+
+/*
+ * "Redo" the breakpoints cleared by a previous "undo", re-inserting the
+ * breakpoint opcodes and updating the "original opcode" values.
+ *
+ * Unlocks the breakpoint set, which must be held by a previous "undo".
+ */
+void dvmRedoBreakpoints(Method* method);
+#endif
+
#endif /*_DALVIK_INTERP_INTERP*/