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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/204017">204017</a></dd>
<dt>Author</dt> <dd>bshafiei@apple.com</dd>
<dt>Date</dt> <dd>2016-08-01 23:51:31 -0700 (Mon, 01 Aug 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/204010">r204010</a>. rdar://problem/27534844</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#branchessafari602branchSourceJavaScriptCoreChangeLog">branches/safari-602-branch/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#branchessafari602branchSourceJavaScriptCoreinterpreterStackVisitorcpp">branches/safari-602-branch/Source/JavaScriptCore/interpreter/StackVisitor.cpp</a></li>
<li><a href="#branchessafari602branchSourceJavaScriptCorejitJITOperationscpp">branches/safari-602-branch/Source/JavaScriptCore/jit/JITOperations.cpp</a></li>
<li><a href="#branchessafari602branchSourceJavaScriptCoreruntimeCommonSlowPathscpp">branches/safari-602-branch/Source/JavaScriptCore/runtime/CommonSlowPaths.cpp</a></li>
<li><a href="#branchessafari602branchSourceJavaScriptCoreruntimeVMh">branches/safari-602-branch/Source/JavaScriptCore/runtime/VM.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="branchessafari602branchSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/JavaScriptCore/ChangeLog (204016 => 204017)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/JavaScriptCore/ChangeLog 2016-08-02 06:51:26 UTC (rev 204016)
+++ branches/safari-602-branch/Source/JavaScriptCore/ChangeLog 2016-08-02 06:51:31 UTC (rev 204017)
</span><span class="lines">@@ -1,5 +1,52 @@
</span><span class="cx"> 2016-08-01 Babak Shafiei <bshafiei@apple.com>
</span><span class="cx">
</span><ins>+ Merge r204010. rdar://problem/27534844
+
+ 2016-08-01 Filip Pizlo <fpizlo@apple.com>
+
+ REGRESSION (r203990): JSC Debug test stress/arity-check-ftl-throw.js failing
+ https://bugs.webkit.org/show_bug.cgi?id=160438
+
+ Reviewed by Mark Lam.
+
+ In r203990 I fixed a bug where CommonSlowPaths.h/arityCheckFor() was basically failing at
+ catching stack overflow due to large parameter count. It would only catch regular old stack
+ overflow, like if the frame pointer was already past the limit.
+
+ This had a secondary problem: unfortunately all of our tests for what happens when you overflow
+ the stack due to large parameter count were not going down that path at all, so we haven't had
+ test coverage for this in ages. There were bugs in all tiers of the engine when handling this
+ case.
+
+ We need to be able to roll back the topCallFrame on paths that are meant to throw an exception
+ from the caller. Otherwise, we'd crash in StackVisitor because it would see a busted stack
+ frame. Rolling back like this "just works" except when the caller is the VM entry frame. I had
+ some choices here. I could have forced anyone who is rolling back to always skip VM entry
+ frames. They can't do it in a way that changes the value of VM::topVMEntryFrame, which is what
+ a stack frame roll back normally does, since exception unwinding needs to see the current value
+ of topVMEntryFrame. So, we have a choice to either try to magically avoid all of the paths that
+ look at topCallFrame, or give topCallFrame a state that unambiguously signals that we are
+ sitting right on top of a VM entry frame without having succeeded at making a JS call. The only
+ place that really needs to know is StackVisitor, which wants to start scanning at topCallFrame.
+ To signal this, I could have either made topCallFrame point to the real top JS call frame
+ without also rolling back topVMEntryFrame, or I could make topCallFrame == topVMEntryFrame. The
+ latter felt somehow cleaner. I filed a bug (https://bugs.webkit.org/show_bug.cgi?id=160441) for
+ converting topCallFrame to a void*, which would give us a chance to harden the rest of the
+ engine against this case.
+
+ * interpreter/StackVisitor.cpp:
+ (JSC::StackVisitor::StackVisitor):
+ We may do ShadowChicken processing, which invokes StackVisitor, when we have topCallFrame
+ pointing at topVMEntryFrame. This teaches StackVisitor how to handle this case. I believe that
+ StackVisitor is the only place that needs to be taught about this at this time, because it's
+ one of the few things that access topCallFrame along this special path.
+
+ * jit/JITOperations.cpp: Roll back the top call frame.
+ * runtime/CommonSlowPaths.cpp:
+ (JSC::SLOW_PATH_DECL): Roll back the top call frame.
+
+2016-08-01 Babak Shafiei <bshafiei@apple.com>
+
</ins><span class="cx"> Merge r203990. rdar://problem/27534844
</span><span class="cx">
</span><span class="cx"> 2016-08-01 Filip Pizlo <fpizlo@apple.com>
</span></span></pre></div>
<a id="branchessafari602branchSourceJavaScriptCoreinterpreterStackVisitorcpp"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/JavaScriptCore/interpreter/StackVisitor.cpp (204016 => 204017)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/JavaScriptCore/interpreter/StackVisitor.cpp 2016-08-02 06:51:26 UTC (rev 204016)
+++ branches/safari-602-branch/Source/JavaScriptCore/interpreter/StackVisitor.cpp 2016-08-02 06:51:31 UTC (rev 204017)
</span><span class="lines">@@ -43,6 +43,11 @@
</span><span class="cx"> if (startFrame) {
</span><span class="cx"> m_frame.m_VMEntryFrame = startFrame->vm().topVMEntryFrame;
</span><span class="cx"> topFrame = startFrame->vm().topCallFrame;
</span><ins>+
+ if (topFrame && static_cast<void*>(m_frame.m_VMEntryFrame) == static_cast<void*>(topFrame)) {
+ topFrame = vmEntryRecord(m_frame.m_VMEntryFrame)->m_prevTopCallFrame;
+ m_frame.m_VMEntryFrame = vmEntryRecord(m_frame.m_VMEntryFrame)->m_prevTopVMEntryFrame;
+ }
</ins><span class="cx"> } else {
</span><span class="cx"> m_frame.m_VMEntryFrame = 0;
</span><span class="cx"> topFrame = 0;
</span></span></pre></div>
<a id="branchessafari602branchSourceJavaScriptCorejitJITOperationscpp"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/JavaScriptCore/jit/JITOperations.cpp (204016 => 204017)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/JavaScriptCore/jit/JITOperations.cpp 2016-08-02 06:51:26 UTC (rev 204016)
+++ branches/safari-602-branch/Source/JavaScriptCore/jit/JITOperations.cpp 2016-08-02 06:51:31 UTC (rev 204017)
</span><span class="lines">@@ -2172,7 +2172,7 @@
</span><span class="cx">
</span><span class="cx"> void JIT_OPERATION lookupExceptionHandlerFromCallerFrame(VM* vm, ExecState* exec)
</span><span class="cx"> {
</span><del>- NativeCallFrameTracer tracer(vm, exec);
</del><ins>+ vm->topCallFrame = exec->callerFrame();
</ins><span class="cx"> genericUnwind(vm, exec, UnwindFromCallerFrame);
</span><span class="cx"> ASSERT(vm->targetMachinePCForThrow);
</span><span class="cx"> }
</span></span></pre></div>
<a id="branchessafari602branchSourceJavaScriptCoreruntimeCommonSlowPathscpp"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/JavaScriptCore/runtime/CommonSlowPaths.cpp (204016 => 204017)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/JavaScriptCore/runtime/CommonSlowPaths.cpp 2016-08-02 06:51:26 UTC (rev 204016)
+++ branches/safari-602-branch/Source/JavaScriptCore/runtime/CommonSlowPaths.cpp 2016-08-02 06:51:31 UTC (rev 204017)
</span><span class="lines">@@ -181,7 +181,8 @@
</span><span class="cx"> int slotsToAdd = CommonSlowPaths::arityCheckFor(exec, vm, CodeForCall);
</span><span class="cx"> if (slotsToAdd < 0) {
</span><span class="cx"> exec = exec->callerFrame();
</span><del>- ErrorHandlingScope errorScope(exec->vm());
</del><ins>+ vm.topCallFrame = exec;
+ ErrorHandlingScope errorScope(vm);
</ins><span class="cx"> CommonSlowPaths::interpreterThrowInCaller(exec, createStackOverflowError(exec));
</span><span class="cx"> RETURN_TWO(bitwise_cast<void*>(static_cast<uintptr_t>(1)), exec);
</span><span class="cx"> }
</span><span class="lines">@@ -194,7 +195,8 @@
</span><span class="cx"> int slotsToAdd = CommonSlowPaths::arityCheckFor(exec, vm, CodeForConstruct);
</span><span class="cx"> if (slotsToAdd < 0) {
</span><span class="cx"> exec = exec->callerFrame();
</span><del>- ErrorHandlingScope errorScope(exec->vm());
</del><ins>+ vm.topCallFrame = exec;
+ ErrorHandlingScope errorScope(vm);
</ins><span class="cx"> CommonSlowPaths::interpreterThrowInCaller(exec, createStackOverflowError(exec));
</span><span class="cx"> RETURN_TWO(bitwise_cast<void*>(static_cast<uintptr_t>(1)), exec);
</span><span class="cx"> }
</span></span></pre></div>
<a id="branchessafari602branchSourceJavaScriptCoreruntimeVMh"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/JavaScriptCore/runtime/VM.h (204016 => 204017)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/JavaScriptCore/runtime/VM.h 2016-08-02 06:51:26 UTC (rev 204016)
+++ branches/safari-602-branch/Source/JavaScriptCore/runtime/VM.h 2016-08-02 06:51:31 UTC (rev 204017)
</span><span class="lines">@@ -278,7 +278,11 @@
</span><span class="cx"> VMType vmType;
</span><span class="cx"> ClientData* clientData;
</span><span class="cx"> VMEntryFrame* topVMEntryFrame;
</span><del>- ExecState* topCallFrame;
</del><ins>+ // NOTE: When throwing an exception while rolling back the call frame, this may be equal to
+ // topVMEntryFrame.
+ // FIXME: This should be a void*, because it might not point to a CallFrame.
+ // https://bugs.webkit.org/show_bug.cgi?id=160441
+ ExecState* topCallFrame;
</ins><span class="cx"> Strong<Structure> structureStructure;
</span><span class="cx"> Strong<Structure> structureRareDataStructure;
</span><span class="cx"> Strong<Structure> terminatedExecutionErrorStructure;
</span></span></pre>
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