Re: [drlvm][regression] jvmti single step is broken

Sat, 20 Oct 2007 06:04:47 -0700 

Gregory Shimansky wrote:

Alexei Fedotov wrote:

Hello Gregory,
I have filed a bug [1] which may be caused by your recent changes.



Hello Alexei. Thanks for noticing this. I am indeed in the the process 
of changing JVMTI single step code, and this assertion failure did 
happen because of my recent changes. I changed the prediction code for 
invokevirtual and invokeinterface bytecodes.



Previously JVMTI code contained a switch based on the call instruction's 
1st operand kind. If it was Kind_Mem, then the bytecode was treated as 
invokevirtual. If instruction was Kind_Reg, then it was treated as 
invokeinterface. But I changed the code to actually taking bytecode in 
question from the method's bytecode array and switch now knows exactly 
what type of invoke is in the method.



For invokevirtual bytecode on x86 it is expected to have a call[base + 
index*scale + disp] instruction that calls a virtual method, where 
(base) contains the address of VTable, and (index*scale + disp) contain 
offset in vtable (disp is usually null in the code generated by JET).



But here is some strange situation, and I'd like to hear JIT gurus to 
tell me what has happened. The method is



org/apache/harmony/test/stress/jpda/jdwp/share/JDWPQALogWriter.println(Ljava/lang/String;)V 



Its bytecode 15 looks like this in java:


 15: invokevirtual #6=<Method java.lang.StringBuilder.append 
(java.lang.String)java.lang.StringBuilder>


But generated code this bytecode looks like this:

0282E164  mov         edx,dword ptr [ebp-0F0h]
0282E16A  sub         esp,0Ch
0282E16D  mov         dword ptr [esp],2C719A8h
0282E174  mov         dword ptr [esp+4],6
0282E17C  mov         dword ptr [esp+8],edx
0282E180  mov         dword ptr [ebp-0F0h],edx
0282E186  mov         dword ptr [ebp-0D4h],3
0282E190  mov         dword ptr [ebp-0E0h],7
0282E19A  mov         eax,12D1620h
0282E19F  call        eax
0282E1A1  sub         esp,8
0282E1A4  mov         ecx,dword ptr [ebp-0F4h]
0282E1AA  mov         dword ptr [esp],ecx
0282E1AD  mov         ecx,dword ptr [ebp-0F0h]
0282E1B3  mov         dword ptr [esp+4],ecx
0282E1B7  mov         dword ptr [ebp-0D4h],1
0282E1C1  mov         dword ptr [ebp-0E0h],1
0282E1CB  mov         ecx,dword ptr [eax]
0282E1CD  call        ecx
0282E1CF  mov         dword ptr [ebp-0F0h],eax
0282E1D5  mov         dword ptr [ebp-0D4h],2
0282E1DF  mov         dword ptr [ebp-0E0h],3


The addresses are generated by jvmti_dump_compiled_method function that 
outputs this map:


...
[EMAIL PROTECTED]| STDERR> bytecode 7: 15 = 0282E164
[EMAIL PROTECTED]| STDERR>
[EMAIL PROTECTED]| STDERR> bytecode 8: 18 = 0282E1E9
...


In the above assembly I see two calls, both of type Kind_Reg. But this 
code is compiled for invokevirtual. Before my change this code would be 
treated as invokeinterface, and an attempt would be to find a compiled 
method based on the value of ECX.



I made a fix at 586707 to treat all calls through a register as direct 
calls to method's compiled code. This means that register calls cannot 
be encountered to call a stub for method's compilation or resolution. 
The address has to be pointing to method's body. Otherwise it isn't 
possible for JVMTI code to figure out exactly what method is called by 
invokevirtual bytecode.



I wonder how to get VTable and offset out of the above code, and why is 
the difference from the usual call [base + index*scale + disp]?



[1] http://issues.apache.org/jira/browse/HARMONY-4981

On 10/19/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:

Author: gshimansky
Date: Fri Oct 19 04:09:47 2007
New Revision: 586379

URL: http://svn.apache.org/viewvc?rev=586379&view=rev
Log:

Improved JVMTI for handling invokevirtual and invokeinterface on 
x86_64 architecture.

Capabilities for breakpoint and single step are turned on.


Modified:
   harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_break_intf.h
   harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_internal.h
   harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_break.cpp
   harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_capability.cpp
   harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_step.cpp


Modified: 
harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_break_intf.h
URL: 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_break_intf.h?rev=586379&r1=586378&r2=586379&view=diff 

============================================================================== 

--- harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_break_intf.h 
(original)
+++ harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_break_intf.h 
Fri Oct 19 04:09:47 2007

@@ -78,7 +78,7 @@
 };

 // Pointer to interface callback function

-typedef bool (*BPInterfaceCallBack)(TIEnv *env, VMBreakPoint* bp, 
POINTER_SIZE_INT data);
+typedef bool (*BPInterfaceCallBack)(TIEnv *env, const VMBreakPoint* 
bp, const POINTER_SIZE_INT data);

 typedef bool (*BPInterfaceProcedure) (VMBreakPoint *bp);

 class VMBreakPoints


Modified: 
harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_internal.h
URL: 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_internal.h?rev=586379&r1=586378&r2=586379&view=diff 

============================================================================== 

--- harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_internal.h 
(original)
+++ harmony/enhanced/drlvm/trunk/vm/vmcore/include/jvmti_internal.h 
Fri Oct 19 04:09:47 2007

@@ -423,6 +423,6 @@
    unsigned location, jvmti_StepLocation **next_step, unsigned *count);

 // Callback function for JVMTI breakpoint processing

-bool jvmti_process_breakpoint_event(TIEnv *env, VMBreakPoint* bp, 
POINTER_SIZE_INT data);
+bool jvmti_process_breakpoint_event(TIEnv *env, const VMBreakPoint* 
bp, const POINTER_SIZE_INT data);


 #endif /* _JVMTI_INTERNAL_H_ */


Modified: 
harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_break.cpp
URL: 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_break.cpp?rev=586379&r1=586378&r2=586379&view=diff 

============================================================================== 

--- harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_break.cpp 
(original)
+++ harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_break.cpp 
Fri Oct 19 04:09:47 2007

@@ -39,7 +39,7 @@


 // Callback function for JVMTI breakpoint processing

-bool jvmti_process_breakpoint_event(TIEnv *env, VMBreakPoint* bp, 
POINTER_SIZE_INT UNREF data)
+bool jvmti_process_breakpoint_event(TIEnv *env, const VMBreakPoint* 
bp, const POINTER_SIZE_INT UNREF data)

 {
    assert(bp);



Modified: 
harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_capability.cpp
URL: 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_capability.cpp?rev=586379&r1=586378&r2=586379&view=diff 

============================================================================== 

--- 
harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_capability.cpp 
(original)
+++ 
harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_capability.cpp 
Fri Oct 19 04:09:47 2007

@@ -87,10 +87,10 @@
    1, // can_get_source_debug_extension
    1, // can_access_local_variables
    0, // can_maintain_original_method_order
-    0, // can_generate_single_step_events
+    1, // can_generate_single_step_events
    1, // can_generate_exception_events
    1, // can_generate_frame_pop_events
-    0, // can_generate_breakpoint_events
+    1, // can_generate_breakpoint_events
    1, // can_suspend
    0, // can_redefine_any_class
    1, // can_get_current_thread_cpu_time


Modified: 
harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_step.cpp
URL: 
http://svn.apache.org/viewvc/harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_step.cpp?rev=586379&r1=586378&r2=586379&view=diff 

============================================================================== 

--- harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_step.cpp 
(original)
+++ harmony/enhanced/drlvm/trunk/vm/vmcore/src/jvmti/jvmti_step.cpp 
Fri Oct 19 04:09:47 2007

@@ -494,8 +494,8 @@
    }
 }


-static void jvmti_start_single_step_in_virtual_method(DebugUtilsTI 
*ti, VMBreakPoint* bp,
-                                                      
POINTER_SIZE_INT data)
+static void jvmti_start_single_step_in_virtual_method(DebugUtilsTI 
*ti, const VMBreakPoint* bp,

+    const POINTER_SIZE_INT data, const unsigned char bytecode)
 {
 #if (defined _IA32_) || (defined _EM64T_)
    VM_thread *vm_thread = p_TLS_vmthread;
@@ -517,11 +517,11 @@

    const InstructionDisassembler::Opnd& op = disasm->get_opnd(0);
    Method *method;
-    if (op.kind == InstructionDisassembler::Kind_Mem)
+    if (bytecode == OPCODE_INVOKEVIRTUAL)
    {
        // Invokevirtual uses indirect call from VTable. The base
        // address is in the register, offset is in displacement *
-        // scale. This method is much faster than
+        // scale.
        VTable* vtable = (VTable*)disasm->get_reg_value(op.base, &regs);
        assert(vtable);
        // For x86 based architectures offset cannot be longer than 32
@@ -530,7 +530,7 @@
            op.scale + op.disp);
        method = class_get_method_from_vt_offset(vtable, offset);
    }
-    else if (op.kind == InstructionDisassembler::Kind_Reg)
+    else if (bytecode == OPCODE_INVOKEINTERFACE)
    {
        // This is invokeinterface bytecode which uses register
        // call so we need to search through all methods for this
@@ -577,7 +577,7 @@

 // Callback function for JVMTI single step processing

 static bool jvmti_process_jit_single_step_event(TIEnv* UNREF 
unused_env,
-                                                VMBreakPoint* bp, 
POINTER_SIZE_INT data)

+    const VMBreakPoint* bp, const POINTER_SIZE_INT data)
 {
    assert(bp);

@@ -610,7 +610,10 @@

    if ((bool)data)
    {
-        jvmti_start_single_step_in_virtual_method(ti, bp, data);

+        const unsigned char *bytecode = reinterpret_cast<Method 
*>(method)->get_byte_code_addr();

+        const unsigned char bc = bytecode[location];

+        assert(bc == OPCODE_INVOKEINTERFACE || bc == 
OPCODE_INVOKEVIRTUAL);

+        jvmti_start_single_step_in_virtual_method(ti, bp, data, bc);
        return true;
    }













--
Gregory























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