[NOT TO COMMIT!] Merge Chromium-specific changes in tcmalloc thru. the original gperftools r136.

third_party/tcmalloc/chromium/src/windows/port.cc

Index: third_party/tcmalloc/chromium/src/windows/port.cc
diff --git a/third_party/tcmalloc/chromium/src/windows/port.cc b/third_party/tcmalloc/chromium/src/windows/port.cc
index e68de163d3ef91229ed305af8148d394710223d4..0205912bd6761a2f09a50c8fba0a762adb06d3ad 100644
--- a/third_party/tcmalloc/chromium/src/windows/port.cc
+++ b/third_party/tcmalloc/chromium/src/windows/port.cc
@@ -61,7 +61,7 @@ int getpagesize() {
   return pagesize;
 }
 
-extern "C" PERFTOOLS_DLL_DECL void* __sbrk(ptrdiff_t increment) {
+extern "C" PERFTOOLS_DLL_DECL void* __sbrk(std::ptrdiff_t increment) {
   LOG(FATAL, "Windows doesn't implement sbrk!\n");
   return NULL;
 }
@@ -154,7 +154,8 @@ static void NTAPI on_tls_callback(HINSTANCE h, DWORD dwReason, PVOID pv) {
 extern "C" {
 // This tells the linker to run these functions.
 #pragma data_seg(push, old_seg)
-#pragma data_seg(".CRT$XLB")
+  // Use CRT$XLY instead of CRT$XLB to ensure we're called LATER in sequence.
+#pragma data_seg(".CRT$XLY")
 void (NTAPI *p_thread_callback_tcmalloc)(
     HINSTANCE h, DWORD dwReason, PVOID pv) = on_tls_callback;
 #pragma data_seg(".CRT$XTU")
@@ -227,35 +228,102 @@ extern void* TCMalloc_SystemAlloc(size_t size, size_t *actual_size,
   if (alignment < pagesize) alignment = pagesize;
   size = ((size + alignment - 1) / alignment) * alignment;
 
-  // Safest is to make actual_size same as input-size.
+  // Report the total number of bytes the OS actually delivered.  This might be
+  // greater than |size| because of alignment concerns.  The full size is
+  // necessary so that adjacent spans can be coalesced.
+  // TODO(antonm): proper processing of alignments
+  // in actual_size and decommitting.
   if (actual_size) {
     *actual_size = size;
   }
 
-  // Ask for extra memory if alignment > pagesize
-  size_t extra = 0;
-  if (alignment > pagesize) {
-    extra = alignment - pagesize;
-  }
+  // We currently do not support alignments larger than the pagesize or
+  // alignments that are not multiples of the pagesize after being floored.
+  // If this ability is needed it can be done by the caller (assuming it knows
+  // the page size).
+  assert(alignment <= pagesize);
 
-  void* result = VirtualAlloc(0, size + extra,
+  void* result = VirtualAlloc(0, size,
                               MEM_COMMIT|MEM_RESERVE, PAGE_READWRITE);
   if (result == NULL)
     return NULL;
 
-  // Adjust the return memory so it is aligned
-  uintptr_t ptr = reinterpret_cast<uintptr_t>(result);
-  size_t adjust = 0;
-  if ((ptr & (alignment - 1)) != 0) {
-    adjust = alignment - (ptr & (alignment - 1));
+  // If the result is not aligned memory fragmentation will result which can
+  // lead to pathological memory use.
+  assert((reinterpret_cast<uintptr_t>(result) & (alignment - 1)) == 0);
+
+  return result;
+}
+
+size_t TCMalloc_SystemAddGuard(void* start, size_t size) {
+  static size_t pagesize = 0;
+  if (pagesize == 0) {
+    SYSTEM_INFO system_info;
+    GetSystemInfo(&system_info);
+    pagesize = system_info.dwPageSize;
+  }
+
+  // We know that TCMalloc_SystemAlloc will give us a correct page alignment
+  // regardless, so we can just assert to detect erroneous callers.
+  assert(reinterpret_cast<size_t>(start) % pagesize == 0);
+
+  // Add a guard page to catch metadata corruption. We're using the
+  // PAGE_GUARD flag rather than NO_ACCESS because we want the unique
+  // exception in crash reports.
+  DWORD permissions = 0;
+  if (size > pagesize &&
+      VirtualProtect(start, pagesize, PAGE_READONLY | PAGE_GUARD,
+                     &permissions)) {
+    return pagesize;
   }
 
-  ptr += adjust;
-  return reinterpret_cast<void*>(ptr);
+  return 0;
 }
 
 void TCMalloc_SystemRelease(void* start, size_t length) {
-  // TODO(csilvers): should I be calling VirtualFree here?
+  if (VirtualFree(start, length, MEM_DECOMMIT))
+    return;
+
+  // The decommit may fail if the memory region consists of allocations
+  // from more than one call to VirtualAlloc.  In this case, fall back to
+  // using VirtualQuery to retrieve the allocation boundaries and decommit
+  // them each individually.
+
+  char* ptr = static_cast<char*>(start);
+  char* end = ptr + length;
+  MEMORY_BASIC_INFORMATION info;
+  while (ptr < end) {
+    size_t resultSize = VirtualQuery(ptr, &info, sizeof(info));
+    assert(resultSize == sizeof(info));
+    size_t decommitSize = std::min<size_t>(info.RegionSize, end - ptr);
+    BOOL success = VirtualFree(ptr, decommitSize, MEM_DECOMMIT);
+    assert(success == TRUE);
+    ptr += decommitSize;
+  }
+}
+
+void TCMalloc_SystemCommit(void* start, size_t length) {
+  if (VirtualAlloc(start, length, MEM_COMMIT, PAGE_READWRITE) == start)
+    return;
+
+  // The commit may fail if the memory region consists of allocations
+  // from more than one call to VirtualAlloc.  In this case, fall back to
+  // using VirtualQuery to retrieve the allocation boundaries and commit them
+  // each individually.
+
+  char* ptr = static_cast<char*>(start);
+  char* end = ptr + length;
+  MEMORY_BASIC_INFORMATION info;
+  while (ptr < end) {
+    size_t resultSize = VirtualQuery(ptr, &info, sizeof(info));
+    assert(resultSize == sizeof(info));
+
+    size_t commitSize = std::min<size_t>(info.RegionSize, end - ptr);
+    void* newAddress = VirtualAlloc(ptr, commitSize, MEM_COMMIT,
+                                    PAGE_READWRITE);
+    assert(newAddress == ptr);
+    ptr += commitSize;
+  }
 }
 
 bool RegisterSystemAllocator(SysAllocator *allocator, int priority) {