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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/200035">200035</a></dd>
<dt>Author</dt> <dd>ggaren@apple.com</dd>
<dt>Date</dt> <dd>2016-04-25 11:20:58 -0700 (Mon, 25 Apr 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>2016-04-25 Geoffrey Garen <ggaren@apple.com>
bmalloc: vm allocations should plant guard pages
https://bugs.webkit.org/show_bug.cgi?id=156937
Rolling back in <a href="http://trac.webkit.org/projects/webkit/changeset/199936">r199936</a> with a fix for the memory regression.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourcebmallocChangeLog">trunk/Source/bmalloc/ChangeLog</a></li>
<li><a href="#trunkSourcebmallocbmallocObjecth">trunk/Source/bmalloc/bmalloc/Object.h</a></li>
<li><a href="#trunkSourcebmallocbmallocVMAllocateh">trunk/Source/bmalloc/bmalloc/VMAllocate.h</a></li>
<li><a href="#trunkSourcebmallocbmallocVMHeapcpp">trunk/Source/bmalloc/bmalloc/VMHeap.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourcebmallocChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/ChangeLog (200034 => 200035)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/ChangeLog        2016-04-25 17:48:46 UTC (rev 200034)
+++ trunk/Source/bmalloc/ChangeLog        2016-04-25 18:20:58 UTC (rev 200035)
</span><span class="lines">@@ -1,3 +1,10 @@
</span><ins>+2016-04-25 Geoffrey Garen <ggaren@apple.com>
+
+ bmalloc: vm allocations should plant guard pages
+ https://bugs.webkit.org/show_bug.cgi?id=156937
+
+ Rolling back in r199936 with a fix for the memory regression.
+
</ins><span class="cx"> 2016-04-23 Gavin Barraclough <barraclough@apple.com>
</span><span class="cx">
</span><span class="cx"> bmalloc: vm allocations should plant guard pages
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocObjecth"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/Object.h (200034 => 200035)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/Object.h        2016-04-25 17:48:46 UTC (rev 200034)
+++ trunk/Source/bmalloc/bmalloc/Object.h        2016-04-25 18:20:58 UTC (rev 200035)
</span><span class="lines">@@ -52,6 +52,7 @@
</span><span class="cx"> SmallPage* page();
</span><span class="cx">
</span><span class="cx"> Object operator+(size_t);
</span><ins>+ Object operator-(size_t);
</ins><span class="cx"> bool operator<=(const Object&);
</span><span class="cx">
</span><span class="cx"> private:
</span><span class="lines">@@ -64,6 +65,11 @@
</span><span class="cx"> return Object(m_chunk, m_offset + offset);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+inline Object Object::operator-(size_t offset)
+{
+ return Object(m_chunk, m_offset - offset);
+}
+
</ins><span class="cx"> inline bool Object::operator<=(const Object& other)
</span><span class="cx"> {
</span><span class="cx"> BASSERT(m_chunk == other.m_chunk);
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocVMAllocateh"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/VMAllocate.h (200034 => 200035)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/VMAllocate.h        2016-04-25 17:48:46 UTC (rev 200034)
+++ trunk/Source/bmalloc/bmalloc/VMAllocate.h        2016-04-25 18:20:58 UTC (rev 200035)
</span><span class="lines">@@ -137,6 +137,12 @@
</span><span class="cx"> munmap(p, vmSize);
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+inline void vmRevokePermissions(void* p, size_t vmSize)
+{
+ vmValidate(p, vmSize);
+ mprotect(p, vmSize, PROT_NONE);
+}
+
</ins><span class="cx"> // Allocates vmSize bytes at a specified power-of-two alignment.
</span><span class="cx"> // Use this function to create maskable memory regions.
</span><span class="cx">
</span></span></pre></div>
<a id="trunkSourcebmallocbmallocVMHeapcpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/bmalloc/bmalloc/VMHeap.cpp (200034 => 200035)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/bmalloc/bmalloc/VMHeap.cpp        2016-04-25 17:48:46 UTC (rev 200034)
+++ trunk/Source/bmalloc/bmalloc/VMHeap.cpp        2016-04-25 18:20:58 UTC (rev 200035)
</span><span class="lines">@@ -29,7 +29,7 @@
</span><span class="cx">
</span><span class="cx"> namespace bmalloc {
</span><span class="cx">
</span><del>-XLargeRange VMHeap::tryAllocateLargeChunk(std::lock_guard<StaticMutex>& lock, size_t alignment, size_t size)
</del><ins>+XLargeRange VMHeap::tryAllocateLargeChunk(std::lock_guard<StaticMutex>&, size_t alignment, size_t size)
</ins><span class="cx"> {
</span><span class="cx"> // We allocate VM in aligned multiples to increase the chances that
</span><span class="cx"> // the OS will provide contiguous ranges that we can merge.
</span><span class="lines">@@ -47,7 +47,7 @@
</span><span class="cx"> if (!memory)
</span><span class="cx"> return XLargeRange();
</span><span class="cx">
</span><del>- Chunk* chunk = new (memory) Chunk(lock);
</del><ins>+ Chunk* chunk = static_cast<Chunk*>(memory);
</ins><span class="cx">
</span><span class="cx"> #if BOS(DARWIN)
</span><span class="cx"> m_zone.addChunk(chunk);
</span><span class="lines">@@ -58,13 +58,6 @@
</span><span class="cx">
</span><span class="cx"> void VMHeap::allocateSmallChunk(std::lock_guard<StaticMutex>& lock, size_t pageClass)
</span><span class="cx"> {
</span><del>- Chunk* chunk =
- new (vmAllocate(chunkSize, chunkSize)) Chunk(lock);
-
-#if BOS(DARWIN)
- m_zone.addChunk(chunk);
-#endif
-
</del><span class="cx"> size_t pageSize = bmalloc::pageSize(pageClass);
</span><span class="cx"> size_t smallPageCount = pageSize / smallPageSize;
</span><span class="cx">
</span><span class="lines">@@ -72,12 +65,28 @@
</span><span class="cx"> // aligned allocation requests at equal and smaller powers of two.
</span><span class="cx"> size_t metadataSize = divideRoundingUp(sizeof(Chunk), pageSize) * pageSize;
</span><span class="cx">
</span><ins>+ void* memory = vmAllocate(chunkSize, chunkSize);
+ Chunk* chunk = static_cast<Chunk*>(memory);
+
</ins><span class="cx"> Object begin(chunk, metadataSize);
</span><span class="cx"> Object end(chunk, chunkSize);
</span><span class="cx">
</span><ins>+ // Establish guard pages before writing to Chunk memory to work around
+ // an edge case in the Darwin VM system (<rdar://problem/25910098>).
+ vmRevokePermissions(begin.begin(), pageSize);
+ vmRevokePermissions(end.begin() - pageSize, pageSize);
+
+ begin = begin + pageSize;
+ end = end - pageSize;
+
+ new (chunk) Chunk(lock);
+
+#if BOS(DARWIN)
+ m_zone.addChunk(chunk);
+#endif
+
</ins><span class="cx"> for (Object it = begin; it + pageSize <= end; it = it + pageSize) {
</span><span class="cx"> SmallPage* page = it.page();
</span><del>- new (page) SmallPage;
</del><span class="cx">
</span><span class="cx"> for (size_t i = 0; i < smallPageCount; ++i)
</span><span class="cx"> page[i].setSlide(i);
</span></span></pre>
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