| /* |
| * 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: |
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| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
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| * in the documentation and/or other materials provided with the |
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| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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| */ |
| |
| #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. |
| // |
| // 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 a single (reasonably predicatable) branch 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 are provided at this time: |
| // - Linear overflows cannot corrupt into the partition. |
| // - Linear overflows cannot corrupt out of the partition. |
| // - Freed pages will only be re-used within the partition. |
| // (exception: large allocations > ~1MB) |
| // - Freed pages will only hold same-sized objects when re-used. |
| // - Dereference of freelist pointer should fault. |
| // - Out-of-line main metadata: linear over or underflow cannot corrupt it. |
| // - Partial pointer overwrite of freelist pointer should fault. |
| // - Rudimentary double-free detection. |
| // - Large allocations (> ~1MB) are guard-paged at the beginning and end. |
| // |
| // 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/PageAllocator.h" |
| #include "wtf/SpinLock.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; |
| static const size_t kGenericNumBucketsPerOrderBits = 3; // Eight buckets per order (for the higher orders), e.g. order 8 is 128, 144, 160, ..., 240 |
| 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; |
| int16_t numAllocatedSlots; // Deliberately signed, 0 for empty or decommitted page, -n for full pages. |
| 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; |
| uint16_t numSystemPagesPerSlotSpan; |
| uint16_t numFullPages; |
| }; |
| |
| // 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 int 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 { |
| int 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); |
| |
| WTF_EXPORT void partitionDumpStats(PartitionRoot*, const char* partitionName, bool isLightDump, PartitionStatsDumper*); |
| WTF_EXPORT void partitionDumpStatsGeneric(PartitionRootGeneric*, const char* partitionName, bool isLightDump, PartitionStatsDumper*); |
| |
| 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) |
| { |
| #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR) |
| void* result = malloc(size); |
| RELEASE_ASSERT(result); |
| return result; |
| #else |
| size = partitionCookieSizeAdjustAdd(size); |
| ASSERT(root->initialized); |
| size_t index = size >> kBucketShift; |
| ASSERT(index < root->numBuckets); |
| ASSERT(size == index << kBucketShift); |
| PartitionBucket* bucket = &root->buckets()[index]; |
| return partitionBucketAlloc(root, 0, size, bucket); |
| #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)); |
| RELEASE_ASSERT_WITH_SECURITY_IMPLICATION(ptr != freelistHead); // Catches an immediate double free. |
| ASSERT_WITH_SECURITY_IMPLICATION(!freelistHead || ptr != partitionFreelistMask(freelistHead->next)); // Look for double free one level deeper in debug. |
| 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 |
| 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) |
| { |
| #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR) |
| void* result = malloc(size); |
| RELEASE_ASSERT(result); |
| return result; |
| #else |
| ASSERT(root->initialized); |
| size = partitionCookieSizeAdjustAdd(size); |
| PartitionBucket* bucket = partitionGenericSizeToBucket(root, size); |
| spinLockLock(&root->lock); |
| void* ret = partitionBucketAlloc(root, flags, size, bucket); |
| spinLockUnlock(&root->lock); |
| return ret; |
| #endif |
| } |
| |
| ALWAYS_INLINE void* partitionAllocGeneric(PartitionRootGeneric* root, size_t size) |
| { |
| return partitionAllocGenericFlags(root, 0, size); |
| } |
| |
| ALWAYS_INLINE void partitionFreeGeneric(PartitionRootGeneric* root, void* ptr) |
| { |
| #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR) |
| free(ptr); |
| #else |
| ASSERT(root->initialized); |
| |
| if (UNLIKELY(!ptr)) |
| return; |
| |
| ptr = partitionCookieFreePointerAdjust(ptr); |
| ASSERT(partitionPointerIsValid(ptr)); |
| PartitionPage* page = partitionPointerToPage(ptr); |
| spinLockLock(&root->lock); |
| partitionFreeWithPage(ptr, page); |
| spinLockUnlock(&root->lock); |
| #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 |