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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #if V8_TARGET_ARCH_X87
      6 
      7 #include "src/debug/debug.h"
      8 
      9 #include "src/codegen.h"
     10 #include "src/debug/liveedit.h"
     11 #include "src/x87/frames-x87.h"
     12 
     13 namespace v8 {
     14 namespace internal {
     15 
     16 #define __ ACCESS_MASM(masm)
     17 
     18 
     19 void EmitDebugBreakSlot(MacroAssembler* masm) {
     20   Label check_codesize;
     21   __ bind(&check_codesize);
     22   __ Nop(Assembler::kDebugBreakSlotLength);
     23   DCHECK_EQ(Assembler::kDebugBreakSlotLength,
     24             masm->SizeOfCodeGeneratedSince(&check_codesize));
     25 }
     26 
     27 
     28 void DebugCodegen::GenerateSlot(MacroAssembler* masm, RelocInfo::Mode mode) {
     29   // Generate enough nop's to make space for a call instruction.
     30   masm->RecordDebugBreakSlot(mode);
     31   EmitDebugBreakSlot(masm);
     32 }
     33 
     34 
     35 void DebugCodegen::ClearDebugBreakSlot(Isolate* isolate, Address pc) {
     36   CodePatcher patcher(isolate, pc, Assembler::kDebugBreakSlotLength);
     37   EmitDebugBreakSlot(patcher.masm());
     38 }
     39 
     40 
     41 void DebugCodegen::PatchDebugBreakSlot(Isolate* isolate, Address pc,
     42                                        Handle<Code> code) {
     43   DCHECK(code->is_debug_stub());
     44   static const int kSize = Assembler::kDebugBreakSlotLength;
     45   CodePatcher patcher(isolate, pc, kSize);
     46 
     47   // Add a label for checking the size of the code used for returning.
     48   Label check_codesize;
     49   patcher.masm()->bind(&check_codesize);
     50   patcher.masm()->call(code->entry(), RelocInfo::NONE32);
     51   // Check that the size of the code generated is as expected.
     52   DCHECK_EQ(kSize, patcher.masm()->SizeOfCodeGeneratedSince(&check_codesize));
     53 }
     54 
     55 bool DebugCodegen::DebugBreakSlotIsPatched(Address pc) {
     56   return !Assembler::IsNop(pc);
     57 }
     58 
     59 void DebugCodegen::GenerateDebugBreakStub(MacroAssembler* masm,
     60                                           DebugBreakCallHelperMode mode) {
     61   __ RecordComment("Debug break");
     62 
     63   // Enter an internal frame.
     64   {
     65     FrameScope scope(masm, StackFrame::INTERNAL);
     66 
     67     // Load padding words on stack.
     68     for (int i = 0; i < LiveEdit::kFramePaddingInitialSize; i++) {
     69       __ push(Immediate(Smi::FromInt(LiveEdit::kFramePaddingValue)));
     70     }
     71     __ push(Immediate(Smi::FromInt(LiveEdit::kFramePaddingInitialSize)));
     72 
     73     // Push arguments for DebugBreak call.
     74     if (mode == SAVE_RESULT_REGISTER) {
     75       // Break on return.
     76       __ push(eax);
     77     } else {
     78       // Non-return breaks.
     79       __ Push(masm->isolate()->factory()->the_hole_value());
     80     }
     81     __ Move(eax, Immediate(1));
     82     __ mov(ebx,
     83            Immediate(ExternalReference(
     84                Runtime::FunctionForId(Runtime::kDebugBreak), masm->isolate())));
     85 
     86     CEntryStub ceb(masm->isolate(), 1);
     87     __ CallStub(&ceb);
     88 
     89     if (FLAG_debug_code) {
     90       for (int i = 0; i < kNumJSCallerSaved; ++i) {
     91         Register reg = {JSCallerSavedCode(i)};
     92         // Do not clobber eax if mode is SAVE_RESULT_REGISTER. It will
     93         // contain return value of the function.
     94         if (!(reg.is(eax) && (mode == SAVE_RESULT_REGISTER))) {
     95           __ Move(reg, Immediate(kDebugZapValue));
     96         }
     97       }
     98     }
     99 
    100     __ pop(ebx);
    101     // We divide stored value by 2 (untagging) and multiply it by word's size.
    102     STATIC_ASSERT(kSmiTagSize == 1 && kSmiShiftSize == 0);
    103     __ lea(esp, Operand(esp, ebx, times_half_pointer_size, 0));
    104 
    105     // Get rid of the internal frame.
    106   }
    107 
    108   // This call did not replace a call , so there will be an unwanted
    109   // return address left on the stack. Here we get rid of that.
    110   __ add(esp, Immediate(kPointerSize));
    111 
    112   // Now that the break point has been handled, resume normal execution by
    113   // jumping to the target address intended by the caller and that was
    114   // overwritten by the address of DebugBreakXXX.
    115   ExternalReference after_break_target =
    116       ExternalReference::debug_after_break_target_address(masm->isolate());
    117   __ jmp(Operand::StaticVariable(after_break_target));
    118 }
    119 
    120 
    121 void DebugCodegen::GenerateFrameDropperLiveEdit(MacroAssembler* masm) {
    122   // We do not know our frame height, but set esp based on ebp.
    123   __ lea(esp, Operand(ebp, FrameDropperFrameConstants::kFunctionOffset));
    124   __ pop(edi);  // Function.
    125   __ add(esp, Immediate(-FrameDropperFrameConstants::kCodeOffset));  // INTERNAL
    126                                                                      // frame
    127                                                                      // marker
    128                                                                      // and code
    129   __ pop(ebp);
    130 
    131   ParameterCount dummy(0);
    132   __ CheckDebugHook(edi, no_reg, dummy, dummy);
    133 
    134   // Load context from the function.
    135   __ mov(esi, FieldOperand(edi, JSFunction::kContextOffset));
    136 
    137   // Clear new.target register as a safety measure.
    138   __ mov(edx, masm->isolate()->factory()->undefined_value());
    139 
    140   // Get function code.
    141   __ mov(ebx, FieldOperand(edi, JSFunction::kSharedFunctionInfoOffset));
    142   __ mov(ebx, FieldOperand(ebx, SharedFunctionInfo::kCodeOffset));
    143   __ lea(ebx, FieldOperand(ebx, Code::kHeaderSize));
    144 
    145   // Re-run JSFunction, edi is function, esi is context.
    146   __ jmp(ebx);
    147 }
    148 
    149 
    150 const bool LiveEdit::kFrameDropperSupported = true;
    151 
    152 #undef __
    153 
    154 }  // namespace internal
    155 }  // namespace v8
    156 
    157 #endif  // V8_TARGET_ARCH_X87
    158