bmalloc: vm allocations should plant guard pages

https://bugs.webkit.org/show_bug.cgi?id=156937

Rolling out - looks like this is memory regression.

* bmalloc/Object.h:
(bmalloc::Object::operator+):
(bmalloc::Object::operator<=):
(bmalloc::Object::operator-): Deleted.
* bmalloc/VMAllocate.h:
(bmalloc::vmDeallocate):
(bmalloc::vmRevokePermissions): Deleted.
* bmalloc/VMHeap.cpp:
(bmalloc::VMHeap::allocateSmallChunk):



Canonical link: https://commits.webkit.org/175058@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@199950 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/bmalloc/ChangeLog

@@ -1,3 +1,20 @@
+2016-04-23  Gavin Barraclough  <barraclough@apple.com>
+
+        bmalloc: vm allocations should plant guard pages
+        https://bugs.webkit.org/show_bug.cgi?id=156937
+
+        Rolling out - looks like this is memory regression.
+
+        * bmalloc/Object.h:
+        (bmalloc::Object::operator+):
+        (bmalloc::Object::operator<=):
+        (bmalloc::Object::operator-): Deleted.
+        * bmalloc/VMAllocate.h:
+        (bmalloc::vmDeallocate):
+        (bmalloc::vmRevokePermissions): Deleted.
+        * bmalloc/VMHeap.cpp:
+        (bmalloc::VMHeap::allocateSmallChunk):
+
 2016-04-22  Geoffrey Garen  <ggaren@apple.com>
 
         bmalloc: vm allocations should plant guard pages

Source/bmalloc/bmalloc/Object.h

@@ -52,7 +52,6 @@ class Object {
     SmallPage* page();
 
     Object operator+(size_t);
-    Object operator-(size_t);
     bool operator<=(const Object&);
 
 private:
@@ -65,11 +64,6 @@ inline Object Object::operator+(size_t offset)
     return Object(m_chunk, m_offset + offset);
 }
 
-inline Object Object::operator-(size_t offset)
-{
-    return Object(m_chunk, m_offset - offset);
-}
-
 inline bool Object::operator<=(const Object& other)
 {
     BASSERT(m_chunk == other.m_chunk);

Source/bmalloc/bmalloc/VMAllocate.h

@@ -137,12 +137,6 @@ inline void vmDeallocate(void* p, size_t vmSize)
     munmap(p, vmSize);
 }
 
-inline void vmRevokePermissions(void* p, size_t vmSize)
-{
-    vmValidate(p, vmSize);
-    mprotect(p, vmSize, PROT_NONE);
-}
-
 // Allocates vmSize bytes at a specified power-of-two alignment.
 // Use this function to create maskable memory regions.
 

Source/bmalloc/bmalloc/VMHeap.cpp

@@ -75,12 +75,6 @@ void VMHeap::allocateSmallChunk(std::lock_guard<StaticMutex>& lock, size_t pageC
     Object begin(chunk, metadataSize);
     Object end(chunk, chunkSize);
 
-    vmRevokePermissions(begin.begin(), pageSize);
-    vmRevokePermissions(end.begin() - pageSize, pageSize);
-
-    begin = begin + pageSize;
-    end = end - pageSize;
-
     for (Object it = begin; it + pageSize <= end; it = it + pageSize) {
         SmallPage* page = it.page();
         new (page) SmallPage;