Support for .raSearch in the x86 stackwalker

Patch by Benjamin Smedberg <bsmedberg@gmail.com>


git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@927 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/google_breakpad/processor/stackwalker.h

@@ -108,6 +108,15 @@ class Stackwalker {
   // Returns false otherwise.
   bool InstructionAddressSeemsValid(u_int64_t address);
 
+  template<typename InstructionType>
+  bool ScanForReturnAddress(InstructionType location_start,
+                            InstructionType *location_found,
+                            InstructionType *ip_found) {
+    const int kRASearchWords = 30;
+    return ScanForReturnAddress(location_start, location_found, ip_found,
+                                kRASearchWords);
+  }
+
   // Scan the stack starting at location_start, looking for an address
   // that looks like a valid instruction pointer. Addresses must
   // 1) be contained in the current stack memory
@@ -120,10 +129,10 @@ class Stackwalker {
   template<typename InstructionType>
   bool ScanForReturnAddress(InstructionType location_start,
                             InstructionType *location_found,
-                            InstructionType *ip_found) {
-    const int kRASearchWords = 30;
+                            InstructionType *ip_found,
+                            int searchwords) {
     for (InstructionType location = location_start;
-         location <= location_start + kRASearchWords * sizeof(InstructionType);
+         location <= location_start + searchwords * sizeof(InstructionType);
          location += sizeof(InstructionType)) {
       InstructionType ip;
       if (!memory_->GetMemoryAtAddress(location, &ip))

src/processor/stackwalker_x86.cc

@@ -203,10 +203,21 @@ StackFrameX86 *StackwalkerX86::GetCallerByWindowsFrameInfo(
   dictionary[".cbCalleeParams"] = last_frame_callee_parameter_size;
   dictionary[".cbSavedRegs"] = last_frame_info->saved_register_size;
   dictionary[".cbLocals"] = last_frame_info->local_size;
-  dictionary[".raSearchStart"] = last_frame->context.esp +
-                                 last_frame_callee_parameter_size +
-                                 last_frame_info->local_size +
-                                 last_frame_info->saved_register_size;
+
+  u_int32_t raSearchStart = last_frame->context.esp +
+                            last_frame_callee_parameter_size +
+                            last_frame_info->local_size +
+                            last_frame_info->saved_register_size;
+  u_int32_t found; // dummy value
+  // Scan up to three words above the calculated search value, in case
+  // the stack was aligned to a quadword boundary.
+  ScanForReturnAddress(raSearchStart, &raSearchStart, &found, 3);
+  
+  // The difference between raSearch and raSearchStart is unknown,
+  // but making them the same seems to work well in practice.
+  dictionary[".raSearchStart"] = raSearchStart;
+  dictionary[".raSearch"] = raSearchStart;
+
   dictionary[".cbParams"] = last_frame_info->parameter_size;
 
   // Decide what type of program string to use. The program string is in

src/processor/stackwalker_x86_unittest.cc

@@ -399,6 +399,67 @@ TEST_F(GetCallerFrame, WindowsFrameData) {
   EXPECT_EQ(NULL, frame1->windows_frame_info);
 }
 
+// Use Windows frame data (a "STACK WIN 4" record, from a
+// FrameTypeFrameData DIA record) to walk a stack frame where the stack
+// is aligned and we must search
+TEST_F(GetCallerFrame, WindowsFrameDataAligned) {
+  SetModuleSymbols(&module1,
+                   "STACK WIN 4 aa85 176 0 0 4 4 8 0 1"
+		   " $T1 .raSearch ="
+		   " $T0 $T1 4 - 8 @ ="
+		   " $ebp $T1 4 - ^ ="
+		   " $eip $T1 ^ ="
+		   " $esp $T1 4 + =");
+  Label frame1_esp, frame1_ebp;
+  stack_section.start() = 0x80000000;
+  stack_section
+    // frame 0
+    .D32(0x0ffa0ffa)                    // unused saved register
+    .D32(0xdeaddead)                    // locals
+    .D32(0xbeefbeef)
+    .D32(0)                             // 8-byte alignment
+    .D32(frame1_ebp)
+    .D32(0x5000129d)                    // return address
+    // frame 1
+    .Mark(&frame1_esp)
+    .D32(0x1)                           // parameter
+    .Mark(&frame1_ebp)
+    .D32(0)                             // saved %ebp (stack end)
+    .D32(0);                            // saved %eip (stack end)
+
+  RegionFromSection();
+  raw_context.eip = 0x4000aa85;
+  raw_context.esp = stack_section.start().Value();
+  raw_context.ebp = 0xf052c1de;         // should not be needed to walk frame
+
+  StackwalkerX86 walker(&system_info, &raw_context, &stack_region, &modules,
+                        &supplier, &resolver);
+  ASSERT_TRUE(walker.Walk(&call_stack));
+  frames = call_stack.frames();
+  ASSERT_EQ(2U, frames->size());
+
+  StackFrameX86 *frame0 = static_cast<StackFrameX86 *>(frames->at(0));
+  EXPECT_EQ(StackFrame::FRAME_TRUST_CONTEXT, frame0->trust);
+  ASSERT_EQ(StackFrameX86::CONTEXT_VALID_ALL, frame0->context_validity);
+  EXPECT_EQ(0x4000aa85U, frame0->instruction);
+  EXPECT_EQ(0x4000aa85U, frame0->context.eip);
+  EXPECT_EQ(stack_section.start().Value(), frame0->context.esp);
+  EXPECT_EQ(0xf052c1deU, frame0->context.ebp);
+  EXPECT_TRUE(frame0->windows_frame_info != NULL);
+
+  StackFrameX86 *frame1 = static_cast<StackFrameX86 *>(frames->at(1));
+  EXPECT_EQ(StackFrame::FRAME_TRUST_CFI, frame1->trust);
+  ASSERT_EQ((StackFrameX86::CONTEXT_VALID_EIP
+             | StackFrameX86::CONTEXT_VALID_ESP
+             | StackFrameX86::CONTEXT_VALID_EBP),
+            frame1->context_validity);
+  EXPECT_EQ(0x5000129dU, frame1->instruction + 1);
+  EXPECT_EQ(0x5000129dU, frame1->context.eip);
+  EXPECT_EQ(frame1_esp.Value(), frame1->context.esp);
+  EXPECT_EQ(frame1_ebp.Value(), frame1->context.ebp);
+  EXPECT_EQ(NULL, frame1->windows_frame_info);
+}
+
 // Use Windows frame data (a "STACK WIN 4" record, from a
 // FrameTypeFrameData DIA record) to walk a frame, and depend on the
 // parameter size from the callee as well.