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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/175684">175684</a></dd>
<dt>Author</dt> <dd>bshafiei@apple.com</dd>
<dt>Date</dt> <dd>2014-11-05 22:53:25 -0800 (Wed, 05 Nov 2014)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merged rr175653. rdar://problem/18801123</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#tagsSafari60118SourceJavaScriptCoreChangeLog">tags/Safari-601.1.8/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#tagsSafari60118SourceJavaScriptCorejitRepatchcpp">tags/Safari-601.1.8/Source/JavaScriptCore/jit/Repatch.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="tagsSafari60118SourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: tags/Safari-601.1.8/Source/JavaScriptCore/ChangeLog (175683 => 175684)</h4>
<pre class="diff"><span>
<span class="info">--- tags/Safari-601.1.8/Source/JavaScriptCore/ChangeLog 2014-11-06 06:33:50 UTC (rev 175683)
+++ tags/Safari-601.1.8/Source/JavaScriptCore/ChangeLog 2014-11-06 06:53:25 UTC (rev 175684)
</span><span class="lines">@@ -1,3 +1,37 @@
</span><ins>+2014-11-05 Babak Shafiei <bshafiei@apple.com>
+
+ Merge rr175653.
+
+ 2014-11-05 Mark Lam <mark.lam@apple.com>
+
+ PutById inline caches should have a store barrier when it triggers a structure transition.
+ <https://webkit.org/b/138441>
+
+ Reviewed by Geoffrey Garen.
+
+ After r174025, we no longer insert DFG store barriers when the payload of a
+ PutById operation is not a cell. However, this can lead to a crash when we have
+ PutById inline cache code transitioning the structure and re-allocating the
+ butterfly of an old gen object. The lack of a store barrier in that inline
+ cache results in the old gen object not being noticed during an eden GC scan.
+ As a result, its newly allocated butterfly will not be kept alive, which leads
+ to a stale butterfly pointer and, eventually, a crash.
+
+ It is also possible that the new structure can be collected by the eden GC if
+ (at GC time):
+ 1. It is in the eden gen.
+ 2. The inline cache that installed it has been evicted.
+ 3. There are no live eden gen objects referring to it.
+
+ The chances of this should be more rare than the butterfly re-allocation, but
+ it is still possible. Hence, the fix is to always add a store barrier if the
+ inline caches performs a structure transition.
+
+ * jit/Repatch.cpp:
+ (JSC::emitPutTransitionStub):
+ - Added store barrier code based on SpeculativeJIT::storeToWriteBarrierBuffer()'s
+ implementation.
+
</ins><span class="cx"> 2014-11-04 Mark Lam <mark.lam@apple.com>
</span><span class="cx">
</span><span class="cx"> Rename checkMarkByte() to jumpIfIsRememberedOrInEden().
</span></span></pre></div>
<a id="tagsSafari60118SourceJavaScriptCorejitRepatchcpp"></a>
<div class="modfile"><h4>Modified: tags/Safari-601.1.8/Source/JavaScriptCore/jit/Repatch.cpp (175683 => 175684)</h4>
<pre class="diff"><span>
<span class="info">--- tags/Safari-601.1.8/Source/JavaScriptCore/jit/Repatch.cpp 2014-11-06 06:33:50 UTC (rev 175683)
+++ tags/Safari-601.1.8/Source/JavaScriptCore/jit/Repatch.cpp 2014-11-06 06:53:25 UTC (rev 175684)
</span><span class="lines">@@ -1113,6 +1113,39 @@
</span><span class="cx"> }
</span><span class="cx"> #endif
</span><span class="cx">
</span><ins>+ ScratchBuffer* scratchBuffer = nullptr;
+
+#if ENABLE(GGC)
+ MacroAssembler::Call callFlushWriteBarrierBuffer;
+ MacroAssembler::Jump ownerIsRememberedOrInEden = stubJit.jumpIfIsRememberedOrInEden(baseGPR);
+ {
+ WriteBarrierBuffer* writeBarrierBuffer = &stubJit.vm()->heap.writeBarrierBuffer();
+ stubJit.move(MacroAssembler::TrustedImmPtr(writeBarrierBuffer), scratchGPR1);
+ stubJit.load32(MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::currentIndexOffset()), scratchGPR2);
+ MacroAssembler::Jump needToFlush =
+ stubJit.branch32(MacroAssembler::AboveOrEqual, scratchGPR2, MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::capacityOffset()));
+
+ stubJit.add32(MacroAssembler::TrustedImm32(1), scratchGPR2);
+ stubJit.store32(scratchGPR2, MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::currentIndexOffset()));
+
+ stubJit.loadPtr(MacroAssembler::Address(scratchGPR1, WriteBarrierBuffer::bufferOffset()), scratchGPR1);
+ // We use an offset of -sizeof(void*) because we already added 1 to scratchGPR2.
+ stubJit.storePtr(baseGPR, MacroAssembler::BaseIndex(scratchGPR1, scratchGPR2, MacroAssembler::ScalePtr, static_cast<int32_t>(-sizeof(void*))));
+
+ MacroAssembler::Jump doneWithBarrier = stubJit.jump();
+ needToFlush.link(&stubJit);
+
+ scratchBuffer = vm->scratchBufferForSize(allocator.desiredScratchBufferSizeForCall());
+ allocator.preserveUsedRegistersToScratchBufferForCall(stubJit, scratchBuffer, scratchGPR2);
+ stubJit.setupArgumentsWithExecState(baseGPR);
+ callFlushWriteBarrierBuffer = stubJit.call();
+ allocator.restoreUsedRegistersFromScratchBufferForCall(stubJit, scratchBuffer, scratchGPR2);
+
+ doneWithBarrier.link(&stubJit);
+ }
+ ownerIsRememberedOrInEden.link(&stubJit);
+#endif
+
</ins><span class="cx"> MacroAssembler::Jump success;
</span><span class="cx"> MacroAssembler::Jump failure;
</span><span class="cx">
</span><span class="lines">@@ -1133,7 +1166,8 @@
</span><span class="cx"> slowPath.link(&stubJit);
</span><span class="cx">
</span><span class="cx"> allocator.restoreReusedRegistersByPopping(stubJit);
</span><del>- ScratchBuffer* scratchBuffer = vm->scratchBufferForSize(allocator.desiredScratchBufferSizeForCall());
</del><ins>+ if (!scratchBuffer)
+ scratchBuffer = vm->scratchBufferForSize(allocator.desiredScratchBufferSizeForCall());
</ins><span class="cx"> allocator.preserveUsedRegistersToScratchBufferForCall(stubJit, scratchBuffer, scratchGPR1);
</span><span class="cx"> #if USE(JSVALUE64)
</span><span class="cx"> stubJit.setupArgumentsWithExecState(baseGPR, MacroAssembler::TrustedImmPtr(structure), MacroAssembler::TrustedImm32(slot.cachedOffset()), valueGPR);
</span><span class="lines">@@ -1151,6 +1185,9 @@
</span><span class="cx"> patchBuffer.link(failure, failureLabel);
</span><span class="cx"> else
</span><span class="cx"> patchBuffer.link(failureCases, failureLabel);
</span><ins>+#if ENABLE(GGC)
+ patchBuffer.link(callFlushWriteBarrierBuffer, operationFlushWriteBarrierBuffer);
+#endif
</ins><span class="cx"> if (structure->outOfLineCapacity() != oldStructure->outOfLineCapacity()) {
</span><span class="cx"> patchBuffer.link(operationCall, operationReallocateStorageAndFinishPut);
</span><span class="cx"> patchBuffer.link(successInSlowPath, stubInfo.callReturnLocation.labelAtOffset(stubInfo.patch.deltaCallToDone));
</span></span></pre>
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