third_party/WebKit/Source/wtf/allocator/PartitionAlloc.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef WTF_PartitionAlloc_h
#define WTF_PartitionAlloc_h

// DESCRIPTION
// partitionAlloc() / partitionAllocGeneric() and partitionFree() /
// partitionFreeGeneric() are approximately analagous to malloc() and free().
//
// The main difference is that a PartitionRoot / PartitionRootGeneric object
// must be supplied to these functions, representing a specific "heap partition"
// that will be used to satisfy the allocation. Different partitions are
// guaranteed to exist in separate address spaces, including being separate from
// the main system heap. If the contained objects are all freed, physical memory
// is returned to the system but the address space remains reserved.
// See PartitionAlloc.md for other security properties PartitionAlloc provides.
//
// THE ONLY LEGITIMATE WAY TO OBTAIN A PartitionRoot IS THROUGH THE
// SizeSpecificPartitionAllocator / PartitionAllocatorGeneric classes. To
// minimize the instruction count to the fullest extent possible, the
// PartitionRoot is really just a header adjacent to other data areas provided
// by the allocator class.
//
// The partitionAlloc() variant of the API has the following caveats:
// - Allocations and frees against a single partition must be single threaded.
// - Allocations must not exceed a max size, chosen at compile-time via a
// templated parameter to PartitionAllocator.
// - Allocation sizes must be aligned to the system pointer size.
// - Allocations are bucketed exactly according to size.
//
// And for partitionAllocGeneric():
// - Multi-threaded use against a single partition is ok; locking is handled.
// - Allocations of any arbitrary size can be handled (subject to a limit of
// INT_MAX bytes for security reasons).
// - Bucketing is by approximate size, for example an allocation of 4000 bytes
// might be placed into a 4096-byte bucket. Bucket sizes are chosen to try and
// keep worst-case waste to ~10%.
//
// The allocators are designed to be extremely fast, thanks to the following
// properties and design:
// - Just two single (reasonably predicatable) branches in the hot / fast path
//   for both allocating and (significantly) freeing.
// - A minimal number of operations in the hot / fast path, with the slow paths
//   in separate functions, leading to the possibility of inlining.
// - Each partition page (which is usually multiple physical pages) has a
//   metadata structure which allows fast mapping of free() address to an
//   underlying bucket.
// - Supports a lock-free API for fast performance in single-threaded cases.
// - The freelist for a given bucket is split across a number of partition
//   pages, enabling various simple tricks to try and minimize fragmentation.
// - Fine-grained bucket sizes leading to less waste and better packing.
//
// The following security properties could be investigated in the future:
// - Per-object bucketing (instead of per-size) is mostly available at the API,
// but not used yet.
// - No randomness of freelist entries or bucket position.
// - Better checking for wild pointers in free().
// - Better freelist masking function to guarantee fault on 32-bit.

#include "wtf/Assertions.h"
#include "wtf/BitwiseOperations.h"
#include "wtf/ByteSwap.h"
#include "wtf/CPU.h"
#include "wtf/SpinLock.h"
#include "wtf/TypeTraits.h"
#include "wtf/allocator/PageAllocator.h"

#include <limits.h>

#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
#include <stdlib.h>
#endif

#if ENABLE(ASSERT)
#include <string.h>
#endif

namespace WTF {

// Allocation granularity of sizeof(void*) bytes.
static const size_t kAllocationGranularity = sizeof(void*);
static const size_t kAllocationGranularityMask = kAllocationGranularity - 1;
static const size_t kBucketShift = (kAllocationGranularity == 8) ? 3 : 2;

// Underlying partition storage pages are a power-of-two size. It is typical
// for a partition page to be based on multiple system pages. Most references to
// "page" refer to partition pages.
// We also have the concept of "super pages" -- these are the underlying system
// allocations we make. Super pages contain multiple partition pages inside them
// and include space for a small amount of metadata per partition page.
// Inside super pages, we store "slot spans". A slot span is a continguous range
// of one or more partition pages that stores allocations of the same size.
// Slot span sizes are adjusted depending on the allocation size, to make sure
// the packing does not lead to unused (wasted) space at the end of the last
// system page of the span. For our current max slot span size of 64k and other
// constant values, we pack _all_ partitionAllocGeneric() sizes perfectly up
// against the end of a system page.
static const size_t kPartitionPageShift = 14;  // 16KB
static const size_t kPartitionPageSize = 1 << kPartitionPageShift;
static const size_t kPartitionPageOffsetMask = kPartitionPageSize - 1;
static const size_t kPartitionPageBaseMask = ~kPartitionPageOffsetMask;
static const size_t kMaxPartitionPagesPerSlotSpan = 4;

// To avoid fragmentation via never-used freelist entries, we hand out partition
// freelist sections gradually, in units of the dominant system page size.
// What we're actually doing is avoiding filling the full partition page (16 KB)
// with freelist pointers right away. Writing freelist pointers will fault and
// dirty a private page, which is very wasteful if we never actually store
// objects there.
static const size_t kNumSystemPagesPerPartitionPage =
    kPartitionPageSize / kSystemPageSize;
static const size_t kMaxSystemPagesPerSlotSpan =
    kNumSystemPagesPerPartitionPage * kMaxPartitionPagesPerSlotSpan;

// We reserve virtual address space in 2MB chunks (aligned to 2MB as well).
// These chunks are called "super pages". We do this so that we can store
// metadata in the first few pages of each 2MB aligned section. This leads to
// a very fast free(). We specifically choose 2MB because this virtual address
// block represents a full but single PTE allocation on ARM, ia32 and x64.
//
// The layout of the super page is as follows. The sizes below are the same
// for 32 bit and 64 bit.
//
//   | Guard page (4KB)    |
//   | Metadata page (4KB) |
//   | Guard pages (8KB)   |
//   | Slot span           |
//   | Slot span           |
//   | ...                 |
//   | Slot span           |
//   | Guard page (4KB)    |
//
//   - Each slot span is a contiguous range of one or more PartitionPages.
//   - The metadata page has the following format. Note that the PartitionPage
//     that is not at the head of a slot span is "unused". In other words,
//     the metadata for the slot span is stored only in the first PartitionPage
//     of the slot span. Metadata accesses to other PartitionPages are
//     redirected to the first PartitionPage.
//
//     | SuperPageExtentEntry (32B)                 |
//     | PartitionPage of slot span 1 (32B, used)   |
//     | PartitionPage of slot span 1 (32B, unused) |
//     | PartitionPage of slot span 1 (32B, unused) |
//     | PartitionPage of slot span 2 (32B, used)   |
//     | PartitionPage of slot span 3 (32B, used)   |
//     | ...                                        |
//     | PartitionPage of slot span N (32B, unused) |
//
// A direct mapped page has a similar layout to fake it looking like a super
// page:
//
//     | Guard page (4KB)     |
//     | Metadata page (4KB)  |
//     | Guard pages (8KB)    |
//     | Direct mapped object |
//     | Guard page (4KB)     |
//
//    - The metadata page has the following layout:
//
//     | SuperPageExtentEntry (32B)    |
//     | PartitionPage (32B)           |
//     | PartitionBucket (32B)         |
//     | PartitionDirectMapExtent (8B) |
static const size_t kSuperPageShift = 21;  // 2MB
static const size_t kSuperPageSize = 1 << kSuperPageShift;
static const size_t kSuperPageOffsetMask = kSuperPageSize - 1;
static const size_t kSuperPageBaseMask = ~kSuperPageOffsetMask;
static const size_t kNumPartitionPagesPerSuperPage =
    kSuperPageSize / kPartitionPageSize;

static const size_t kPageMetadataShift = 5;  // 32 bytes per partition page.
static const size_t kPageMetadataSize = 1 << kPageMetadataShift;

// The following kGeneric* constants apply to the generic variants of the API.
// The "order" of an allocation is closely related to the power-of-two size of
// the allocation. More precisely, the order is the bit index of the
// most-significant-bit in the allocation size, where the bit numbers starts
// at index 1 for the least-significant-bit.
// In terms of allocation sizes, order 0 covers 0, order 1 covers 1, order 2
// covers 2->3, order 3 covers 4->7, order 4 covers 8->15.
static const size_t kGenericMinBucketedOrder = 4;  // 8 bytes.
static const size_t kGenericMaxBucketedOrder =
    20;  // Largest bucketed order is 1<<(20-1) (storing 512KB -> almost 1MB)
static const size_t kGenericNumBucketedOrders =
    (kGenericMaxBucketedOrder - kGenericMinBucketedOrder) + 1;
// Eight buckets per order (for the higher orders), e.g. order 8 is 128, 144,
// 160, ..., 240:
static const size_t kGenericNumBucketsPerOrderBits = 3;
static const size_t kGenericNumBucketsPerOrder =
    1 << kGenericNumBucketsPerOrderBits;
static const size_t kGenericNumBuckets =
    kGenericNumBucketedOrders * kGenericNumBucketsPerOrder;
static const size_t kGenericSmallestBucket = 1
                                             << (kGenericMinBucketedOrder - 1);
static const size_t kGenericMaxBucketSpacing =
    1 << ((kGenericMaxBucketedOrder - 1) - kGenericNumBucketsPerOrderBits);
static const size_t kGenericMaxBucketed =
    (1 << (kGenericMaxBucketedOrder - 1)) +
    ((kGenericNumBucketsPerOrder - 1) * kGenericMaxBucketSpacing);
static const size_t kGenericMinDirectMappedDownsize =
    kGenericMaxBucketed +
    1;  // Limit when downsizing a direct mapping using realloc().
static const size_t kGenericMaxDirectMapped = INT_MAX - kSystemPageSize;
static const size_t kBitsPerSizet = sizeof(void*) * CHAR_BIT;

// Constants for the memory reclaim logic.
static const size_t kMaxFreeableSpans = 16;

// If the total size in bytes of allocated but not committed pages exceeds this
// value (probably it is a "out of virtual address space" crash),
// a special crash stack trace is generated at |partitionOutOfMemory|.
// This is to distinguish "out of virtual address space" from
// "out of physical memory" in crash reports.
static const size_t kReasonableSizeOfUnusedPages = 1024 * 1024 * 1024;  // 1GiB

#if ENABLE(ASSERT)
// These two byte values match tcmalloc.
static const unsigned char kUninitializedByte = 0xAB;
static const unsigned char kFreedByte = 0xCD;
static const size_t kCookieSize =
    16;  // Handles alignment up to XMM instructions on Intel.
static const unsigned char kCookieValue[kCookieSize] = {
    0xDE, 0xAD, 0xBE, 0xEF, 0xCA, 0xFE, 0xD0, 0x0D,
    0x13, 0x37, 0xF0, 0x05, 0xBA, 0x11, 0xAB, 0x1E};
#endif

struct PartitionBucket;
struct PartitionRootBase;

struct PartitionFreelistEntry {
  PartitionFreelistEntry* next;
};

// Some notes on page states. A page can be in one of four major states:
// 1) Active.
// 2) Full.
// 3) Empty.
// 4) Decommitted.
// An active page has available free slots. A full page has no free slots. An
// empty page has no free slots, and a decommitted page is an empty page that
// had its backing memory released back to the system.
// There are two linked lists tracking the pages. The "active page" list is an
// approximation of a list of active pages. It is an approximation because
// full, empty and decommitted pages may briefly be present in the list until
// we next do a scan over it.
// The "empty page" list is an accurate list of pages which are either empty
// or decommitted.
//
// The significant page transitions are:
// - free() will detect when a full page has a slot free()'d and immediately
// return the page to the head of the active list.
// - free() will detect when a page is fully emptied. It _may_ add it to the
// empty list or it _may_ leave it on the active list until a future list scan.
// - malloc() _may_ scan the active page list in order to fulfil the request.
// If it does this, full, empty and decommitted pages encountered will be
// booted out of the active list. If there are no suitable active pages found,
// an empty or decommitted page (if one exists) will be pulled from the empty
// list on to the active list.
struct PartitionPage {
  PartitionFreelistEntry* freelistHead;
  PartitionPage* nextPage;
  PartitionBucket* bucket;
  // Deliberately signed, 0 for empty or decommitted page, -n for full pages:
  int16_t numAllocatedSlots;
  uint16_t numUnprovisionedSlots;
  uint16_t pageOffset;
  int16_t emptyCacheIndex;  // -1 if not in the empty cache.
};

struct PartitionBucket {
  PartitionPage* activePagesHead;  // Accessed most in hot path => goes first.
  PartitionPage* emptyPagesHead;
  PartitionPage* decommittedPagesHead;
  uint32_t slotSize;
  unsigned numSystemPagesPerSlotSpan : 8;
  unsigned numFullPages : 24;
};

// An "extent" is a span of consecutive superpages. We link to the partition's
// next extent (if there is one) at the very start of a superpage's metadata
// area.
struct PartitionSuperPageExtentEntry {
  PartitionRootBase* root;
  char* superPageBase;
  char* superPagesEnd;
  PartitionSuperPageExtentEntry* next;
};

struct PartitionDirectMapExtent {
  PartitionDirectMapExtent* nextExtent;
  PartitionDirectMapExtent* prevExtent;
  PartitionBucket* bucket;
  size_t mapSize;  // Mapped size, not including guard pages and meta-data.
};

struct WTF_EXPORT PartitionRootBase {
  size_t totalSizeOfCommittedPages;
  size_t totalSizeOfSuperPages;
  size_t totalSizeOfDirectMappedPages;
  // Invariant: totalSizeOfCommittedPages <=
  //                totalSizeOfSuperPages + totalSizeOfDirectMappedPages.
  unsigned numBuckets;
  unsigned maxAllocation;
  bool initialized;
  char* nextSuperPage;
  char* nextPartitionPage;
  char* nextPartitionPageEnd;
  PartitionSuperPageExtentEntry* currentExtent;
  PartitionSuperPageExtentEntry* firstExtent;
  PartitionDirectMapExtent* directMapList;
  PartitionPage* globalEmptyPageRing[kMaxFreeableSpans];
  int16_t globalEmptyPageRingIndex;
  uintptr_t invertedSelf;

  static SpinLock gInitializedLock;
  static bool gInitialized;
  // gSeedPage is used as a sentinel to indicate that there is no page
  // in the active page list. We can use nullptr, but in that case we need
  // to add a null-check branch to the hot allocation path. We want to avoid
  // that.
  static PartitionPage gSeedPage;
  static PartitionBucket gPagedBucket;
  // gOomHandlingFunction is invoked when ParitionAlloc hits OutOfMemory.
  static void (*gOomHandlingFunction)();
};

// Never instantiate a PartitionRoot directly, instead use PartitionAlloc.
struct PartitionRoot : public PartitionRootBase {
  // The PartitionAlloc templated class ensures the following is correct.
  ALWAYS_INLINE PartitionBucket* buckets() {
    return reinterpret_cast<PartitionBucket*>(this + 1);
  }
  ALWAYS_INLINE const PartitionBucket* buckets() const {
    return reinterpret_cast<const PartitionBucket*>(this + 1);
  }
};

// Never instantiate a PartitionRootGeneric directly, instead use
// PartitionAllocatorGeneric.
struct PartitionRootGeneric : public PartitionRootBase {
  SpinLock lock;
  // Some pre-computed constants.
  size_t orderIndexShifts[kBitsPerSizet + 1];
  size_t orderSubIndexMasks[kBitsPerSizet + 1];
  // The bucket lookup table lets us map a size_t to a bucket quickly.
  // The trailing +1 caters for the overflow case for very large allocation
  // sizes.  It is one flat array instead of a 2D array because in the 2D
  // world, we'd need to index array[blah][max+1] which risks undefined
  // behavior.
  PartitionBucket*
      bucketLookups[((kBitsPerSizet + 1) * kGenericNumBucketsPerOrder) + 1];
  PartitionBucket buckets[kGenericNumBuckets];
};

// Flags for partitionAllocGenericFlags.
enum PartitionAllocFlags {
  PartitionAllocReturnNull = 1 << 0,
};

// Struct used to retrieve total memory usage of a partition. Used by
// PartitionStatsDumper implementation.
struct PartitionMemoryStats {
  size_t totalMmappedBytes;        // Total bytes mmaped from the system.
  size_t totalCommittedBytes;      // Total size of commmitted pages.
  size_t totalResidentBytes;       // Total bytes provisioned by the partition.
  size_t totalActiveBytes;         // Total active bytes in the partition.
  size_t totalDecommittableBytes;  // Total bytes that could be decommitted.
  size_t totalDiscardableBytes;    // Total bytes that could be discarded.
};

// Struct used to retrieve memory statistics about a partition bucket. Used by
// PartitionStatsDumper implementation.
struct PartitionBucketMemoryStats {
  bool isValid;      // Used to check if the stats is valid.
  bool isDirectMap;  // True if this is a direct mapping; size will not be
                     // unique.
  uint32_t bucketSlotSize;       // The size of the slot in bytes.
  uint32_t allocatedPageSize;    // Total size the partition page allocated from
                                 // the system.
  uint32_t activeBytes;          // Total active bytes used in the bucket.
  uint32_t residentBytes;        // Total bytes provisioned in the bucket.
  uint32_t decommittableBytes;   // Total bytes that could be decommitted.
  uint32_t discardableBytes;     // Total bytes that could be discarded.
  uint32_t numFullPages;         // Number of pages with all slots allocated.
  uint32_t numActivePages;       // Number of pages that have at least one
                                 // provisioned slot.
  uint32_t numEmptyPages;        // Number of pages that are empty
                                 // but not decommitted.
  uint32_t numDecommittedPages;  // Number of pages that are empty
                                 // and decommitted.
};

// Interface that is passed to partitionDumpStats and
// partitionDumpStatsGeneric for using the memory statistics.
class WTF_EXPORT PartitionStatsDumper {
 public:
  // Called to dump total memory used by partition, once per partition.
  virtual void partitionDumpTotals(const char* partitionName,
                                   const PartitionMemoryStats*) = 0;

  // Called to dump stats about buckets, for each bucket.
  virtual void partitionsDumpBucketStats(const char* partitionName,
                                         const PartitionBucketMemoryStats*) = 0;
};

WTF_EXPORT void partitionAllocGlobalInit(void (*oomHandlingFunction)());
WTF_EXPORT void partitionAllocInit(PartitionRoot*,
                                   size_t numBuckets,
                                   size_t maxAllocation);
WTF_EXPORT bool partitionAllocShutdown(PartitionRoot*);
WTF_EXPORT void partitionAllocGenericInit(PartitionRootGeneric*);
WTF_EXPORT bool partitionAllocGenericShutdown(PartitionRootGeneric*);

enum PartitionPurgeFlags {
  // Decommitting the ring list of empty pages is reasonably fast.
  PartitionPurgeDecommitEmptyPages = 1 << 0,
  // Discarding unused system pages is slower, because it involves walking all
  // freelists in all active partition pages of all buckets >= system page
  // size. It often frees a similar amount of memory to decommitting the empty
  // pages, though.
  PartitionPurgeDiscardUnusedSystemPages = 1 << 1,
};

WTF_EXPORT void partitionPurgeMemory(PartitionRoot*, int);
WTF_EXPORT void partitionPurgeMemoryGeneric(PartitionRootGeneric*, int);

WTF_EXPORT NEVER_INLINE void* partitionAllocSlowPath(PartitionRootBase*,
                                                     int,
                                                     size_t,
                                                     PartitionBucket*);
WTF_EXPORT NEVER_INLINE void partitionFreeSlowPath(PartitionPage*);
WTF_EXPORT NEVER_INLINE void* partitionReallocGeneric(PartitionRootGeneric*,
                                                      void*,
                                                      size_t,
                                                      const char* typeName);

WTF_EXPORT void partitionDumpStats(PartitionRoot*,
                                   const char* partitionName,
                                   bool isLightDump,
                                   PartitionStatsDumper*);
WTF_EXPORT void partitionDumpStatsGeneric(PartitionRootGeneric*,
                                          const char* partitionName,
                                          bool isLightDump,
                                          PartitionStatsDumper*);

class WTF_EXPORT PartitionAllocHooks {
 public:
  typedef void AllocationHook(void* address, size_t, const char* typeName);
  typedef void FreeHook(void* address);

  static void setAllocationHook(AllocationHook* hook) {
    m_allocationHook = hook;
  }
  static void setFreeHook(FreeHook* hook) { m_freeHook = hook; }

  static void allocationHookIfEnabled(void* address,
                                      size_t size,
                                      const char* typeName) {
    AllocationHook* allocationHook = m_allocationHook;
    if (UNLIKELY(allocationHook != nullptr))
      allocationHook(address, size, typeName);
  }

  static void freeHookIfEnabled(void* address) {
    FreeHook* freeHook = m_freeHook;
    if (UNLIKELY(freeHook != nullptr))
      freeHook(address);
  }

  static void reallocHookIfEnabled(void* oldAddress,
                                   void* newAddress,
                                   size_t size,
                                   const char* typeName) {
    // Report a reallocation as a free followed by an allocation.
    AllocationHook* allocationHook = m_allocationHook;
    FreeHook* freeHook = m_freeHook;
    if (UNLIKELY(allocationHook && freeHook)) {
      freeHook(oldAddress);
      allocationHook(newAddress, size, typeName);
    }
  }

 private:
  // Pointers to hook functions that PartitionAlloc will call on allocation and
  // free if the pointers are non-null.
  static AllocationHook* m_allocationHook;
  static FreeHook* m_freeHook;
};

// In official builds, do not include type info string literals to avoid
// bloating the binary.
#if defined(OFFICIAL_BUILD)
#define WTF_HEAP_PROFILER_TYPE_NAME(T) nullptr
#else
#define WTF_HEAP_PROFILER_TYPE_NAME(T) ::WTF::getStringWithTypeName<T>()
#endif

ALWAYS_INLINE PartitionFreelistEntry* partitionFreelistMask(
    PartitionFreelistEntry* ptr) {
// We use bswap on little endian as a fast mask for two reasons:
// 1) If an object is freed and its vtable used where the attacker doesn't
// get the chance to run allocations between the free and use, the vtable
// dereference is likely to fault.
// 2) If the attacker has a linear buffer overflow and elects to try and
// corrupt a freelist pointer, partial pointer overwrite attacks are
// thwarted.
// For big endian, similar guarantees are arrived at with a negation.
#if CPU(BIG_ENDIAN)
  uintptr_t masked = ~reinterpret_cast<uintptr_t>(ptr);
#else
  uintptr_t masked = bswapuintptrt(reinterpret_cast<uintptr_t>(ptr));
#endif
  return reinterpret_cast<PartitionFreelistEntry*>(masked);
}

ALWAYS_INLINE size_t partitionCookieSizeAdjustAdd(size_t size) {
#if ENABLE(ASSERT)
  // Add space for cookies, checking for integer overflow.
  ASSERT(size + (2 * kCookieSize) > size);
  size += 2 * kCookieSize;
#endif
  return size;
}

ALWAYS_INLINE size_t partitionCookieSizeAdjustSubtract(size_t size) {
#if ENABLE(ASSERT)
  // Remove space for cookies.
  ASSERT(size >= 2 * kCookieSize);
  size -= 2 * kCookieSize;
#endif
  return size;
}

ALWAYS_INLINE void* partitionCookieFreePointerAdjust(void* ptr) {
#if ENABLE(ASSERT)
  // The value given to the application is actually just after the cookie.
  ptr = static_cast<char*>(ptr) - kCookieSize;
#endif
  return ptr;
}

ALWAYS_INLINE void partitionCookieWriteValue(void* ptr) {
#if ENABLE(ASSERT)
  unsigned char* cookiePtr = reinterpret_cast<unsigned char*>(ptr);
  for (size_t i = 0; i < kCookieSize; ++i, ++cookiePtr)
    *cookiePtr = kCookieValue[i];
#endif
}

ALWAYS_INLINE void partitionCookieCheckValue(void* ptr) {
#if ENABLE(ASSERT)
  unsigned char* cookiePtr = reinterpret_cast<unsigned char*>(ptr);
  for (size_t i = 0; i < kCookieSize; ++i, ++cookiePtr)
    ASSERT(*cookiePtr == kCookieValue[i]);
#endif
}

ALWAYS_INLINE char* partitionSuperPageToMetadataArea(char* ptr) {
  uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(ptr);
  ASSERT(!(pointerAsUint & kSuperPageOffsetMask));
  // The metadata area is exactly one system page (the guard page) into the
  // super page.
  return reinterpret_cast<char*>(pointerAsUint + kSystemPageSize);
}

ALWAYS_INLINE PartitionPage* partitionPointerToPageNoAlignmentCheck(void* ptr) {
  uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(ptr);
  char* superPagePtr =
      reinterpret_cast<char*>(pointerAsUint & kSuperPageBaseMask);
  uintptr_t partitionPageIndex =
      (pointerAsUint & kSuperPageOffsetMask) >> kPartitionPageShift;
  // Index 0 is invalid because it is the metadata and guard area and
  // the last index is invalid because it is a guard page.
  ASSERT(partitionPageIndex);
  ASSERT(partitionPageIndex < kNumPartitionPagesPerSuperPage - 1);
  PartitionPage* page = reinterpret_cast<PartitionPage*>(
      partitionSuperPageToMetadataArea(superPagePtr) +
      (partitionPageIndex << kPageMetadataShift));
  // Partition pages in the same slot span can share the same page object.
  // Adjust for that.
  size_t delta = page->pageOffset << kPageMetadataShift;
  page =
      reinterpret_cast<PartitionPage*>(reinterpret_cast<char*>(page) - delta);
  return page;
}

ALWAYS_INLINE void* partitionPageToPointer(const PartitionPage* page) {
  uintptr_t pointerAsUint = reinterpret_cast<uintptr_t>(page);
  uintptr_t superPageOffset = (pointerAsUint & kSuperPageOffsetMask);
  ASSERT(superPageOffset > kSystemPageSize);
  ASSERT(superPageOffset < kSystemPageSize + (kNumPartitionPagesPerSuperPage *
                                              kPageMetadataSize));
  uintptr_t partitionPageIndex =
      (superPageOffset - kSystemPageSize) >> kPageMetadataShift;
  // Index 0 is invalid because it is the metadata area and the last index is
  // invalid because it is a guard page.
  ASSERT(partitionPageIndex);
  ASSERT(partitionPageIndex < kNumPartitionPagesPerSuperPage - 1);
  uintptr_t superPageBase = (pointerAsUint & kSuperPageBaseMask);
  void* ret = reinterpret_cast<void*>(
      superPageBase + (partitionPageIndex << kPartitionPageShift));
  return ret;
}

ALWAYS_INLINE PartitionPage* partitionPointerToPage(void* ptr) {
  PartitionPage* page = partitionPointerToPageNoAlignmentCheck(ptr);
  // Checks that the pointer is a multiple of bucket size.
  ASSERT(!((reinterpret_cast<uintptr_t>(ptr) -
            reinterpret_cast<uintptr_t>(partitionPageToPointer(page))) %
           page->bucket->slotSize));
  return page;
}

ALWAYS_INLINE bool partitionBucketIsDirectMapped(
    const PartitionBucket* bucket) {
  return !bucket->numSystemPagesPerSlotSpan;
}

ALWAYS_INLINE size_t partitionBucketBytes(const PartitionBucket* bucket) {
  return bucket->numSystemPagesPerSlotSpan * kSystemPageSize;
}

ALWAYS_INLINE uint16_t partitionBucketSlots(const PartitionBucket* bucket) {
  return static_cast<uint16_t>(partitionBucketBytes(bucket) / bucket->slotSize);
}

ALWAYS_INLINE size_t* partitionPageGetRawSizePtr(PartitionPage* page) {
  // For single-slot buckets which span more than one partition page, we
  // have some spare metadata space to store the raw allocation size. We
  // can use this to report better statistics.
  PartitionBucket* bucket = page->bucket;
  if (bucket->slotSize <= kMaxSystemPagesPerSlotSpan * kSystemPageSize)
    return nullptr;

  ASSERT((bucket->slotSize % kSystemPageSize) == 0);
  ASSERT(partitionBucketIsDirectMapped(bucket) ||
         partitionBucketSlots(bucket) == 1);
  page++;
  return reinterpret_cast<size_t*>(&page->freelistHead);
}

ALWAYS_INLINE size_t partitionPageGetRawSize(PartitionPage* page) {
  size_t* rawSizePtr = partitionPageGetRawSizePtr(page);
  if (UNLIKELY(rawSizePtr != nullptr))
    return *rawSizePtr;
  return 0;
}

ALWAYS_INLINE PartitionRootBase* partitionPageToRoot(PartitionPage* page) {
  PartitionSuperPageExtentEntry* extentEntry =
      reinterpret_cast<PartitionSuperPageExtentEntry*>(
          reinterpret_cast<uintptr_t>(page) & kSystemPageBaseMask);
  return extentEntry->root;
}

ALWAYS_INLINE bool partitionPointerIsValid(void* ptr) {
  PartitionPage* page = partitionPointerToPage(ptr);
  PartitionRootBase* root = partitionPageToRoot(page);
  return root->invertedSelf == ~reinterpret_cast<uintptr_t>(root);
}

ALWAYS_INLINE void* partitionBucketAlloc(PartitionRootBase* root,
                                         int flags,
                                         size_t size,
                                         PartitionBucket* bucket) {
  PartitionPage* page = bucket->activePagesHead;
  // Check that this page is neither full nor freed.
  ASSERT(page->numAllocatedSlots >= 0);
  void* ret = page->freelistHead;
  if (LIKELY(ret != 0)) {
    // If these asserts fire, you probably corrupted memory.
    ASSERT(partitionPointerIsValid(ret));
    // All large allocations must go through the slow path to correctly
    // update the size metadata.
    ASSERT(partitionPageGetRawSize(page) == 0);
    PartitionFreelistEntry* newHead =
        partitionFreelistMask(static_cast<PartitionFreelistEntry*>(ret)->next);
    page->freelistHead = newHead;
    page->numAllocatedSlots++;
  } else {
    ret = partitionAllocSlowPath(root, flags, size, bucket);
    ASSERT(!ret || partitionPointerIsValid(ret));
  }
#if ENABLE(ASSERT)
  if (!ret)
    return 0;
  // Fill the uninitialized pattern, and write the cookies.
  page = partitionPointerToPage(ret);
  size_t slotSize = page->bucket->slotSize;
  size_t rawSize = partitionPageGetRawSize(page);
  if (rawSize) {
    ASSERT(rawSize == size);
    slotSize = rawSize;
  }
  size_t noCookieSize = partitionCookieSizeAdjustSubtract(slotSize);
  char* charRet = static_cast<char*>(ret);
  // The value given to the application is actually just after the cookie.
  ret = charRet + kCookieSize;
  memset(ret, kUninitializedByte, noCookieSize);
  partitionCookieWriteValue(charRet);
  partitionCookieWriteValue(charRet + kCookieSize + noCookieSize);
#endif
  return ret;
}

ALWAYS_INLINE void* partitionAlloc(PartitionRoot* root,
                                   size_t size,
                                   const char* typeName) {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  void* result = malloc(size);
  RELEASE_ASSERT(result);
  return result;
#else
  size_t requestedSize = size;
  size = partitionCookieSizeAdjustAdd(size);
  ASSERT(root->initialized);
  size_t index = size >> kBucketShift;
  ASSERT(index < root->numBuckets);
  ASSERT(size == index << kBucketShift);
  PartitionBucket* bucket = &root->buckets()[index];
  void* result = partitionBucketAlloc(root, 0, size, bucket);
  PartitionAllocHooks::allocationHookIfEnabled(result, requestedSize, typeName);
  return result;
#endif  // defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
}

ALWAYS_INLINE void partitionFreeWithPage(void* ptr, PartitionPage* page) {
// If these asserts fire, you probably corrupted memory.
#if ENABLE(ASSERT)
  size_t slotSize = page->bucket->slotSize;
  size_t rawSize = partitionPageGetRawSize(page);
  if (rawSize)
    slotSize = rawSize;
  partitionCookieCheckValue(ptr);
  partitionCookieCheckValue(reinterpret_cast<char*>(ptr) + slotSize -
                            kCookieSize);
  memset(ptr, kFreedByte, slotSize);
#endif
  ASSERT(page->numAllocatedSlots);
  PartitionFreelistEntry* freelistHead = page->freelistHead;
  ASSERT(!freelistHead || partitionPointerIsValid(freelistHead));
  SECURITY_CHECK(ptr != freelistHead);  // Catches an immediate double free.
  // Look for double free one level deeper in debug.
  ASSERT_WITH_SECURITY_IMPLICATION(
      !freelistHead || ptr != partitionFreelistMask(freelistHead->next));
  PartitionFreelistEntry* entry = static_cast<PartitionFreelistEntry*>(ptr);
  entry->next = partitionFreelistMask(freelistHead);
  page->freelistHead = entry;
  --page->numAllocatedSlots;
  if (UNLIKELY(page->numAllocatedSlots <= 0)) {
    partitionFreeSlowPath(page);
  } else {
    // All single-slot allocations must go through the slow path to
    // correctly update the size metadata.
    ASSERT(partitionPageGetRawSize(page) == 0);
  }
}

ALWAYS_INLINE void partitionFree(void* ptr) {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  free(ptr);
#else
  PartitionAllocHooks::freeHookIfEnabled(ptr);
  ptr = partitionCookieFreePointerAdjust(ptr);
  ASSERT(partitionPointerIsValid(ptr));
  PartitionPage* page = partitionPointerToPage(ptr);
  partitionFreeWithPage(ptr, page);
#endif
}

ALWAYS_INLINE PartitionBucket* partitionGenericSizeToBucket(
    PartitionRootGeneric* root,
    size_t size) {
  size_t order = kBitsPerSizet - countLeadingZerosSizet(size);
  // The order index is simply the next few bits after the most significant bit.
  size_t orderIndex = (size >> root->orderIndexShifts[order]) &
                      (kGenericNumBucketsPerOrder - 1);
  // And if the remaining bits are non-zero we must bump the bucket up.
  size_t subOrderIndex = size & root->orderSubIndexMasks[order];
  PartitionBucket* bucket =
      root->bucketLookups[(order << kGenericNumBucketsPerOrderBits) +
                          orderIndex + !!subOrderIndex];
  ASSERT(!bucket->slotSize || bucket->slotSize >= size);
  ASSERT(!(bucket->slotSize % kGenericSmallestBucket));
  return bucket;
}

ALWAYS_INLINE void* partitionAllocGenericFlags(PartitionRootGeneric* root,
                                               int flags,
                                               size_t size,
                                               const char* typeName) {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  void* result = malloc(size);
  RELEASE_ASSERT(result || flags & PartitionAllocReturnNull);
  return result;
#else
  ASSERT(root->initialized);
  size_t requestedSize = size;
  size = partitionCookieSizeAdjustAdd(size);
  PartitionBucket* bucket = partitionGenericSizeToBucket(root, size);
  void* ret = nullptr;
  {
    SpinLock::Guard guard(root->lock);
// TODO(bashi): Remove following RELEAE_ASSERT()s once we find the cause of
// http://crbug.com/514141
#if OS(ANDROID)
    RELEASE_ASSERT(bucket >= &root->buckets[0] ||
                   bucket == &PartitionRootGeneric::gPagedBucket);
    RELEASE_ASSERT(bucket <= &root->buckets[kGenericNumBuckets - 1] ||
                   bucket == &PartitionRootGeneric::gPagedBucket);
    RELEASE_ASSERT(root->initialized);
#endif
    ret = partitionBucketAlloc(root, flags, size, bucket);
  }
  PartitionAllocHooks::allocationHookIfEnabled(ret, requestedSize, typeName);
  return ret;
#endif
}

ALWAYS_INLINE void* partitionAllocGeneric(PartitionRootGeneric* root,
                                          size_t size,
                                          const char* typeName) {
  return partitionAllocGenericFlags(root, 0, size, typeName);
}

ALWAYS_INLINE void partitionFreeGeneric(PartitionRootGeneric* root, void* ptr) {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  free(ptr);
#else
  ASSERT(root->initialized);

  if (UNLIKELY(!ptr))
    return;

  PartitionAllocHooks::freeHookIfEnabled(ptr);
  ptr = partitionCookieFreePointerAdjust(ptr);
  ASSERT(partitionPointerIsValid(ptr));
  PartitionPage* page = partitionPointerToPage(ptr);
  {
    SpinLock::Guard guard(root->lock);
    partitionFreeWithPage(ptr, page);
  }
#endif
}

ALWAYS_INLINE size_t partitionDirectMapSize(size_t size) {
  // Caller must check that the size is not above the kGenericMaxDirectMapped
  // limit before calling. This also guards against integer overflow in the
  // calculation here.
  ASSERT(size <= kGenericMaxDirectMapped);
  return (size + kSystemPageOffsetMask) & kSystemPageBaseMask;
}

ALWAYS_INLINE size_t partitionAllocActualSize(PartitionRootGeneric* root,
                                              size_t size) {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  return size;
#else
  ASSERT(root->initialized);
  size = partitionCookieSizeAdjustAdd(size);
  PartitionBucket* bucket = partitionGenericSizeToBucket(root, size);
  if (LIKELY(!partitionBucketIsDirectMapped(bucket))) {
    size = bucket->slotSize;
  } else if (size > kGenericMaxDirectMapped) {
    // Too large to allocate => return the size unchanged.
  } else {
    ASSERT(bucket == &PartitionRootBase::gPagedBucket);
    size = partitionDirectMapSize(size);
  }
  return partitionCookieSizeAdjustSubtract(size);
#endif
}

ALWAYS_INLINE bool partitionAllocSupportsGetSize() {
#if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
  return false;
#else
  return true;
#endif
}

ALWAYS_INLINE size_t partitionAllocGetSize(void* ptr) {
  // No need to lock here. Only 'ptr' being freed by another thread could
  // cause trouble, and the caller is responsible for that not happening.
  ASSERT(partitionAllocSupportsGetSize());
  ptr = partitionCookieFreePointerAdjust(ptr);
  ASSERT(partitionPointerIsValid(ptr));
  PartitionPage* page = partitionPointerToPage(ptr);
  size_t size = page->bucket->slotSize;
  return partitionCookieSizeAdjustSubtract(size);
}

// N (or more accurately, N - sizeof(void*)) represents the largest size in
// bytes that will be handled by a SizeSpecificPartitionAllocator.
// Attempts to partitionAlloc() more than this amount will fail.
template <size_t N>
class SizeSpecificPartitionAllocator {
 public:
  static const size_t kMaxAllocation = N - kAllocationGranularity;
  static const size_t kNumBuckets = N / kAllocationGranularity;
  void init() {
    partitionAllocInit(&m_partitionRoot, kNumBuckets, kMaxAllocation);
  }
  bool shutdown() { return partitionAllocShutdown(&m_partitionRoot); }
  ALWAYS_INLINE PartitionRoot* root() { return &m_partitionRoot; }

 private:
  PartitionRoot m_partitionRoot;
  PartitionBucket m_actualBuckets[kNumBuckets];
};

class PartitionAllocatorGeneric {
 public:
  void init() { partitionAllocGenericInit(&m_partitionRoot); }
  bool shutdown() { return partitionAllocGenericShutdown(&m_partitionRoot); }
  ALWAYS_INLINE PartitionRootGeneric* root() { return &m_partitionRoot; }

 private:
  PartitionRootGeneric m_partitionRoot;
};

}  // namespace WTF

using WTF::SizeSpecificPartitionAllocator;
using WTF::PartitionAllocatorGeneric;
using WTF::PartitionRoot;
using WTF::partitionAllocInit;
using WTF::partitionAllocShutdown;
using WTF::partitionAlloc;
using WTF::partitionFree;
using WTF::partitionAllocGeneric;
using WTF::partitionFreeGeneric;
using WTF::partitionReallocGeneric;
using WTF::partitionAllocActualSize;
using WTF::partitionAllocSupportsGetSize;
using WTF::partitionAllocGetSize;

#endif  // WTF_PartitionAlloc_h