Move Partition Allocator into Chromium base.

third_party/WebKit/Source/wtf/allocator/AddressSpaceRandomization.cpp

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "wtf/allocator/AddressSpaceRandomization.h"
-
-#include "wtf/SpinLock.h"
-#include "wtf/allocator/PageAllocator.h"
-
-#if OS(WIN)
-#include <windows.h>
-#else
-#include <sys/time.h>
-#include <unistd.h>
-#endif
-
-namespace WTF {
-
-namespace {
-
-// This is the same PRNG as used by tcmalloc for mapping address randomness;
-// see http://burtleburtle.net/bob/rand/smallprng.html
-struct ranctx {
-  SpinLock lock;
-  bool initialized;
-  uint32_t a;
-  uint32_t b;
-  uint32_t c;
-  uint32_t d;
-};
-
-#define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
-
-uint32_t ranvalInternal(ranctx* x) {
-  uint32_t e = x->a - rot(x->b, 27);
-  x->a = x->b ^ rot(x->c, 17);
-  x->b = x->c + x->d;
-  x->c = x->d + e;
-  x->d = e + x->a;
-  return x->d;
-}
-
-#undef rot
-
-uint32_t ranval(ranctx* x) {
-  SpinLock::Guard guard(x->lock);
-  if (UNLIKELY(!x->initialized)) {
-    x->initialized = true;
-    char c;
-    uint32_t seed = static_cast<uint32_t>(reinterpret_cast<uintptr_t>(&c));
-    uint32_t pid;
-    uint32_t usec;
-#if OS(WIN)
-    pid = GetCurrentProcessId();
-    SYSTEMTIME st;
-    GetSystemTime(&st);
-    usec = static_cast<uint32_t>(st.wMilliseconds * 1000);
-#else
-    pid = static_cast<uint32_t>(getpid());
-    struct timeval tv;
-    gettimeofday(&tv, 0);
-    usec = static_cast<uint32_t>(tv.tv_usec);
-#endif
-    seed ^= pid;
-    seed ^= usec;
-    x->a = 0xf1ea5eed;
-    x->b = x->c = x->d = seed;
-    for (int i = 0; i < 20; ++i) {
-      (void)ranvalInternal(x);
-    }
-  }
-  uint32_t ret = ranvalInternal(x);
-  return ret;
-}
-
-static struct ranctx s_ranctx;
-
-}  // namespace
-
-// Calculates a random preferred mapping address. In calculating an
-// address, we balance good ASLR against not fragmenting the address
-// space too badly.
-void* getRandomPageBase() {
-  uintptr_t random;
-  random = static_cast<uintptr_t>(ranval(&s_ranctx));
-#if CPU(X86_64)
-  random <<= 32UL;
-  random |= static_cast<uintptr_t>(ranval(&s_ranctx));
-// This address mask gives a low liklihood of address space collisions.
-// We handle the situation gracefully if there is a collision.
-#if OS(WIN)
-  // 64-bit Windows has a bizarrely small 8TB user address space.
-  // Allocates in the 1-5TB region.
-  // TODO(cevans): I think Win 8.1 has 47-bits like Linux.
-  random &= 0x3ffffffffffUL;
-  random += 0x10000000000UL;
-#elif defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
-  // This range is copied from the TSan source, but works for all tools.
-  random &= 0x007fffffffffUL;
-  random += 0x7e8000000000UL;
-#else
-  // Linux and OS X support the full 47-bit user space of x64 processors.
-  random &= 0x3fffffffffffUL;
-#endif
-#elif CPU(ARM64)
-  // ARM64 on Linux has 39-bit user space.
-  random &= 0x3fffffffffUL;
-  random += 0x1000000000UL;
-#else  // !CPU(X86_64) && !CPU(ARM64)
-#if OS(WIN)
-  // On win32 host systems the randomization plus huge alignment causes
-  // excessive fragmentation. Plus most of these systems lack ASLR, so the
-  // randomization isn't buying anything. In that case we just skip it.
-  // TODO(jschuh): Just dump the randomization when HE-ASLR is present.
-  static BOOL isWow64 = -1;
-  if (isWow64 == -1 && !IsWow64Process(GetCurrentProcess(), &isWow64))
-    isWow64 = FALSE;
-  if (!isWow64)
-    return nullptr;
-#endif  // OS(WIN)
-  // This is a good range on Windows, Linux and Mac.
-  // Allocates in the 0.5-1.5GB region.
-  random &= 0x3fffffff;
-  random += 0x20000000;
-#endif  // CPU(X86_64)
-  random &= kPageAllocationGranularityBaseMask;
-  return reinterpret_cast<void*>(random);
-}
-
-}  // namespace WTF