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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/245563">245563</a></dd>
<dt>Author</dt> <dd>tzagallo@apple.com</dd>
<dt>Date</dt> <dd>2019-05-20 23:31:06 -0700 (Mon, 20 May 2019)</dd>
</dl>

<h3>Log Message</h3>
<pre>Fix 32-bit btyecode cache crashes
https://bugs.webkit.org/show_bug.cgi?id=198035
<rdar://problem/49905560>

Reviewed by Michael Saboff.

There were 2 32-bit issues with the bytecode cache:
- UnlinkedFunctionExecutable::m_cachedCodeBlockForConstructOffset was not initialized.
  The code was relying on the other member of the union, `m_unlinkedCodeBlockForConstruct`,
  initializing both m_cachedCodeBlockForCallOffset and m_cachedCodeBlockForConstructOffset.
  This is undefined behavior and is also incorrect in 32-bit. Since m_unlinkedCodeBlockForConstruct
  is 32-bit, it only initializes the first member of the struct.
- Encoder::Page was not aligned at the end. This lead to unaligned allocations on subsequent
  pages, since the start of the following page would not be aligned.

* runtime/CachedTypes.cpp:
(JSC::Encoder::release):
(JSC::Encoder::Page::alignEnd):
(JSC::Encoder::allocateNewPage):
(JSC::VariableLengthObject::buffer const):
(JSC::VariableLengthObject::allocate):
(JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoreruntimeCachedTypescpp">trunk/Source/JavaScriptCore/runtime/CachedTypes.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (245562 => 245563)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog    2019-05-21 05:31:25 UTC (rev 245562)
+++ trunk/Source/JavaScriptCore/ChangeLog       2019-05-21 06:31:06 UTC (rev 245563)
</span><span class="lines">@@ -1,3 +1,28 @@
</span><ins>+2019-05-20  Tadeu Zagallo  <tzagallo@apple.com>
+
+        Fix 32-bit btyecode cache crashes
+        https://bugs.webkit.org/show_bug.cgi?id=198035
+        <rdar://problem/49905560>
+
+        Reviewed by Michael Saboff.
+
+        There were 2 32-bit issues with the bytecode cache:
+        - UnlinkedFunctionExecutable::m_cachedCodeBlockForConstructOffset was not initialized.
+          The code was relying on the other member of the union, `m_unlinkedCodeBlockForConstruct`,
+          initializing both m_cachedCodeBlockForCallOffset and m_cachedCodeBlockForConstructOffset.
+          This is undefined behavior and is also incorrect in 32-bit. Since m_unlinkedCodeBlockForConstruct
+          is 32-bit, it only initializes the first member of the struct.
+        - Encoder::Page was not aligned at the end. This lead to unaligned allocations on subsequent
+          pages, since the start of the following page would not be aligned.
+
+        * runtime/CachedTypes.cpp:
+        (JSC::Encoder::release):
+        (JSC::Encoder::Page::alignEnd):
+        (JSC::Encoder::allocateNewPage):
+        (JSC::VariableLengthObject::buffer const):
+        (JSC::VariableLengthObject::allocate):
+        (JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):
+
</ins><span class="cx"> 2019-05-20  Ross Kirsling  <ross.kirsling@sony.com>
</span><span class="cx"> 
</span><span class="cx">         [WinCairo] Implement Remote Web Inspector Client.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoreruntimeCachedTypescpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/runtime/CachedTypes.cpp (245562 => 245563)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/runtime/CachedTypes.cpp      2019-05-21 05:31:25 UTC (rev 245562)
+++ trunk/Source/JavaScriptCore/runtime/CachedTypes.cpp 2019-05-21 06:31:06 UTC (rev 245563)
</span><span class="lines">@@ -146,6 +146,10 @@
</span><span class="cx"> 
</span><span class="cx">     Ref<CachedBytecode> release()
</span><span class="cx">     {
</span><ins>+        if (!m_currentPage)
+            return CachedBytecode::create();
+
+        m_currentPage->alignEnd();
</ins><span class="cx">         size_t size = m_baseOffset + m_currentPage->size();
</span><span class="cx">         MallocPtr<uint8_t> buffer = MallocPtr<uint8_t>::malloc(size);
</span><span class="cx">         unsigned offset = 0;
</span><span class="lines">@@ -193,6 +197,15 @@
</span><span class="cx">             return false;
</span><span class="cx">         }
</span><span class="cx"> 
</span><ins>+        void alignEnd()
+        {
+            ptrdiff_t size = roundUpToMultipleOf(alignof(std::max_align_t), m_offset);
+            if (size == m_offset)
+                return;
+            ASSERT(static_cast<size_t>(size) <= m_capacity);
+            m_offset = size;
+        }
+
</ins><span class="cx">     private:
</span><span class="cx">         MallocPtr<uint8_t> m_buffer;
</span><span class="cx">         ptrdiff_t m_offset;
</span><span class="lines">@@ -202,8 +215,10 @@
</span><span class="cx">     void allocateNewPage(size_t size = 0)
</span><span class="cx">     {
</span><span class="cx">         static size_t minPageSize = pageSize();
</span><del>-        if (m_currentPage)
</del><ins>+        if (m_currentPage) {
+            m_currentPage->alignEnd();
</ins><span class="cx">             m_baseOffset += m_currentPage->size();
</span><ins>+        }
</ins><span class="cx">         if (size < minPageSize)
</span><span class="cx">             size = minPageSize;
</span><span class="cx">         else
</span><span class="lines">@@ -383,6 +398,7 @@
</span><span class="cx">     template<typename T>
</span><span class="cx">     const T* buffer() const
</span><span class="cx">     {
</span><ins>+        ASSERT(!(bitwise_cast<uintptr_t>(buffer()) % alignof(T)));
</ins><span class="cx">         return bitwise_cast<const T*>(buffer());
</span><span class="cx">     }
</span><span class="cx"> 
</span><span class="lines">@@ -403,6 +419,7 @@
</span><span class="cx">     T* allocate(Encoder& encoder, unsigned size = 1)
</span><span class="cx">     {
</span><span class="cx">         uint8_t* result = allocate(encoder, sizeof(T) * size);
</span><ins>+        ASSERT(!(bitwise_cast<uintptr_t>(result) % alignof(T)));
</ins><span class="cx">         return new (result) T[size];
</span><span class="cx">     }
</span><span class="cx"> 
</span><span class="lines">@@ -2100,8 +2117,11 @@
</span><span class="cx">                 codeBlockOffset = offset;
</span><span class="cx">                 m_isCached = true;
</span><span class="cx">                 leafExecutables--;
</span><ins>+                return;
</ins><span class="cx">             }
</span><span class="cx">         }
</span><ins>+
+        codeBlockOffset = 0;
</ins><span class="cx">     };
</span><span class="cx"> 
</span><span class="cx">     if (!cachedExecutable.unlinkedCodeBlockForCall().isEmpty() || !cachedExecutable.unlinkedCodeBlockForConstruct().isEmpty()) {
</span><span class="lines">@@ -2109,6 +2129,8 @@
</span><span class="cx">         checkBounds(m_cachedCodeBlockForConstructOffset, cachedExecutable.unlinkedCodeBlockForConstruct());
</span><span class="cx">         if (m_isCached)
</span><span class="cx">             m_decoder = &decoder;
</span><ins>+        else
+            m_decoder = nullptr;
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     if (leafExecutables)
</span></span></pre>
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