[unwinder] Remove final FP bounds check which is invalid on Windows

Bug: v8:9092
Change-Id: I1839651c0a47dbbefa93c7441597c98653132ff8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1554692
Auto-Submit: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60748}

src/unwinder.cc

@@ -80,8 +80,11 @@ bool Unwinder::TryUnwindV8Frames(const UnwindState& unwind_state,
     if (!AddressIsInStack(final_sp, stack_base, stack_top)) return false;
     register_state->sp = final_sp;
 
+    // We don't check that the final FP value is within the stack bounds because
+    // this is just the rbp value that JSEntryStub pushed. On platforms like
+    // Win64 this is not used as a dedicated FP register, and could contain
+    // anything.
     void* final_fp = GetCallerFPFromFP(current_fp);
-    if (!AddressIsInStack(final_fp, stack_base, stack_top)) return false;
     register_state->fp = final_fp;
 
     register_state->pc = next_pc;

test/cctest/test-unwinder.cc

@@ -423,11 +423,13 @@ TEST(Unwind_StackBounds_WithUnwinding) {
                                                  stack_base);
   CHECK(!unwound);
 
-  // Change the return address so that it is not in range.
+  // Change the return address so that it is not in range. We will not range
+  // check the stack[9] FP value because we have finished unwinding and the
+  // contents of rbp does not necessarily have to be the FP in this case.
   stack[10] = 202;
   unwound = v8::Unwinder::TryUnwindV8Frames(unwind_state, &register_state,
                                             stack_base);
-  CHECK(!unwound);
+  CHECK(unwound);
 }
 
 TEST(PCIsInV8_BadState_Fail) {
@@ -482,8 +484,8 @@ TEST(PCIsInV8_InCodeOrEmbeddedRange) {
                       embedded_range_length);
 }
 
-// PCIsInV8 doesn't check if the PC is in JSEntrydirectly. It's assumed that the
-// CodeRange or EmbeddedCodeRange contain JSEntry.
+// PCIsInV8 doesn't check if the PC is in JSEntry directly. It's assumed that
+// the CodeRange or EmbeddedCodeRange contain JSEntry.
 TEST(PCIsInV8_InJSEntryRange) {
   LocalContext env;
   v8::Isolate* isolate = env->GetIsolate();