Allow page allocations to include guard pages

The PageAllocator is in principle capable of using guard pages. We can
expose that functionality to its clients.

Change-Id: I919f6f76310feb160d2b26ac1fc64db4e91804bb
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>

4 files changed, 21 insertions, 10 deletions

diff --git a/src/3rdparty/masm/wtf/PageAllocation.h b/src/3rdparty/masm/wtf/PageAllocation.h
index 18d31880c0..95692be3ae 100644
--- a/src/3rdparty/masm/wtf/PageAllocation.h
+++ b/src/3rdparty/masm/wtf/PageAllocation.h
@@ -87,10 +87,15 @@ public:
     operator bool() const { return PageBlock::operator bool(); }
 #endif
 
-    static PageAllocation allocate(size_t size, OSAllocator::Usage usage = OSAllocator::UnknownUsage, bool writable = true, bool executable = false)
+    static PageAllocation allocate(size_t size,
+                                   OSAllocator::Usage usage = OSAllocator::UnknownUsage,
+                                   bool writable = true, bool executable = false,
+                                   bool includesGuardPages = false)
     {
         ASSERT(isPageAligned(size));
-        return PageAllocation(OSAllocator::reserveAndCommit(size, usage, writable, executable), size);
+        return PageAllocation(OSAllocator::reserveAndCommit(size, usage, writable, executable,
+                                                            includesGuardPages), size,
+                                                            includesGuardPages);
     }
 
     void deallocate()
@@ -103,12 +108,12 @@ public:
         ASSERT(tmp);
         ASSERT(!*this);
 
-        OSAllocator::decommitAndRelease(tmp.base(), tmp.size());
+        OSAllocator::decommitAndRelease(tmp.realBase(), tmp.realSize());
     }
 
 private:
-    PageAllocation(void* base, size_t size)
-        : PageBlock(base, size, false)
+    PageAllocation(void* base, size_t size, bool includesGuardPages = false)
+        : PageBlock(base, size, includesGuardPages)
     {
     }
 };
diff --git a/src/3rdparty/masm/wtf/PageAllocationAligned.cpp b/src/3rdparty/masm/wtf/PageAllocationAligned.cpp
index bdb976b1b7..1c35653381 100644
--- a/src/3rdparty/masm/wtf/PageAllocationAligned.cpp
+++ b/src/3rdparty/masm/wtf/PageAllocationAligned.cpp
@@ -75,10 +75,11 @@ void PageAllocationAligned::deallocate()
     ASSERT(!*this);
 
 #if OS(DARWIN)
-    vm_deallocate(current_task(), reinterpret_cast<vm_address_t>(tmp.base()), tmp.size());
+    vm_deallocate(current_task(), reinterpret_cast<vm_address_t>(tmp.realBase()), tmp.realSize());
 #else
-    ASSERT(tmp.m_reservation.contains(tmp.base(), tmp.size()));
-    OSAllocator::decommitAndRelease(tmp.m_reservation.base(), tmp.m_reservation.size(), tmp.base(), tmp.size());
+    ASSERT(tmp.m_reservation.contains(tmp.realBase(), tmp.realSize()));
+    OSAllocator::decommitAndRelease(tmp.m_reservation.realBase(), tmp.m_reservation.realSize(),
+                                    tmp.realBase(), tmp.realSize());
 #endif
 }
 
diff --git a/src/3rdparty/masm/wtf/PageBlock.h b/src/3rdparty/masm/wtf/PageBlock.h
index 56e5570178..4d408e1c91 100644
--- a/src/3rdparty/masm/wtf/PageBlock.h
+++ b/src/3rdparty/masm/wtf/PageBlock.h
@@ -40,8 +40,13 @@ public:
     PageBlock(const PageBlock&);
     PageBlock(void*, size_t, bool hasGuardPages);
     
+    void* realBase() const { return m_realBase; }
     void* base() const { return m_base; }
-    size_t size() const { return m_size; }
+    size_t size() const
+    {
+        return m_size - 2 * (static_cast<char *>(m_base) - static_cast<char *>(m_realBase));
+    }
+    size_t realSize() const { return m_size; }
 
     operator bool() const { return !!m_realBase; }
 
diff --git a/src/3rdparty/masm/wtf/PageReservation.h b/src/3rdparty/masm/wtf/PageReservation.h
index 77783ebcc4..15be344fa8 100644
--- a/src/3rdparty/masm/wtf/PageReservation.h
+++ b/src/3rdparty/masm/wtf/PageReservation.h
@@ -125,7 +125,7 @@ public:
         ASSERT(tmp);
         ASSERT(!*this);
 
-        OSAllocator::releaseDecommitted(tmp.base(), tmp.size());
+        OSAllocator::releaseDecommitted(tmp.realBase(), tmp.realSize());
     }
 
 private: