1 files changed, 132 insertions, 0 deletions
diff --git a/third_party/base/allocator/partition_allocator/address_space_randomization.cc b/third_party/base/allocator/partition_allocator/address_space_randomization.cc
new file mode 100644
index 0000000000..fdcc5911b9
--- /dev/null
+++ b/third_party/base/allocator/partition_allocator/address_space_randomization.cc
@@ -0,0 +1,132 @@
+// 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 "third_party/base/allocator/partition_allocator/address_space_randomization.h"
+
+#include "third_party/base/allocator/partition_allocator/page_allocator.h"
+#include "third_party/base/allocator/partition_allocator/spin_lock.h"
+#include "third_party/build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#else
+#include <sys/time.h>
+#include <unistd.h>
+#endif
+
+namespace pdfium {
+namespace base {
+
+namespace {
+
+// This is the same PRNG as used by tcmalloc for mapping address randomness;
+// see http://burtleburtle.net/bob/rand/smallprng.html
+struct ranctx {
+  subtle::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) {
+  subtle::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 defined(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 defined(ARCH_CPU_X86_64)
+  random <<= 32UL;
+  random |= static_cast<uintptr_t>(ranval(&s_ranctx));
+// This address mask gives a low likelihood of address space collisions. We
+// handle the situation gracefully if there is a collision.
+#if defined(OS_WIN)
+  // 64-bit Windows has a bizarrely small 8TB user address space. Allocates in
+  // the 1-5TB region. TODO(palmer): See if Windows >= 8.1 has the full 47 bits,
+  // and use it if so. crbug.com/672219
+  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 defined(ARCH_CPU_ARM64)
+  // ARM64 on Linux has 39-bit user space.
+  random &= 0x3fffffffffUL;
+  random += 0x1000000000UL;
+#else  // !defined(ARCH_CPU_X86_64) && !defined(ARCH_CPU_ARM64)
+#if defined(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  // defined(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  // defined(ARCH_CPU_X86_64)
+  random &= kPageAllocationGranularityBaseMask;
+  return reinterpret_cast<void*>(random);
+}
+
+}  // namespace base
+}  // namespace pdfium