[WIP][scudo][standalone] Make secondary cache configurable at runtime

[cryptoad]

Summary

We were requested recently to make the secondary cache more configurable
at runtime, allowing for changes to the maximum number of entries that
the cache can hold, as well as the maximum size of an entry that can be
cached.

The approach chosen is to some mallopt options that allow setting those
at the allocator level.

compiler-rt/lib/scudo/standalone/allocator_config.h

#if SCUDO_CAN_USE_PRIMARY64
   typedef SizeClassAllocator64<SizeClassMap, 28U, 1000, 1000,
                                /*MaySupportMemoryTagging=*/true>
       Primary;
 #else
   // 256KB regions
   typedef SizeClassAllocator32<SizeClassMap, 18U, 1000, 1000> Primary;
 #endif
   // Cache blocks up to 2MB
-  typedef MapAllocator<MapAllocatorCache<32U, 2UL << 20, 0, 1000>> Secondary;
+  typedef MapAllocator<MapAllocatorCache<128U, 32U, 2UL << 20, 0, 1000>>
+      Secondary;
   template <class A>
   using TSDRegistryT = TSDRegistrySharedT<A, 2U>; // Shared, max 2 TSDs.
 };
 
 struct AndroidSvelteConfig {
   using SizeClassMap = SvelteSizeClassMap;
 #if SCUDO_CAN_USE_PRIMARY64
   // 128MB regions
   typedef SizeClassAllocator64<SizeClassMap, 27U, 1000, 1000> Primary;
 #else
   // 64KB regions
   typedef SizeClassAllocator32<SizeClassMap, 16U, 1000, 1000> Primary;
 #endif
-  typedef MapAllocator<MapAllocatorCache<4U, 1UL << 18, 0, 0>> Secondary;
+  typedef MapAllocator<MapAllocatorCache<16U, 4U, 1UL << 18, 0, 0>> Secondary;
   template <class A>
   using TSDRegistryT = TSDRegistrySharedT<A, 1U>; // Shared, only 1 TSD.
 };
 
 #if SCUDO_CAN_USE_PRIMARY64
 struct FuchsiaConfig {
   // 1GB Regions
   typedef SizeClassAllocator64<DefaultSizeClassMap, 30U> Primary;

compiler-rt/lib/scudo/standalone/combined.h

 // This function is not part of the NDK so it does not appear in any public
 // header files. We only declare/use it when targeting the platform.
 extern "C" size_t android_unsafe_frame_pointer_chase(scudo::uptr *buf,
                                                      size_t num_entries);
 #endif
 
 namespace scudo {
 
-enum class Option { ReleaseInterval };
-
 template <class Params, void (*PostInitCallback)(void) = EmptyCallback>
 class Allocator {
 public:
   using PrimaryT = typename Params::Primary;
   using CacheT = typename PrimaryT::CacheT;
   typedef Allocator<Params, PostInitCallback> ThisT;
   typedef typename Params::template TSDRegistryT<ThisT> TSDRegistryT;
 
#endif
   }
 
   bool canReturnNull() {
     initThreadMaybe();
     return Options.MayReturnNull;
   }
 
   bool setOption(Option O, sptr Value) {
-    if (O == Option::ReleaseInterval) {
-      Primary.setReleaseToOsIntervalMs(static_cast<s32>(Value));
-      Secondary.setReleaseToOsIntervalMs(static_cast<s32>(Value));
-      return true;
-    }
-    return false;
+    const bool Result = Primary.setOption(O, Value);
+    return Secondary.setOption(O, Value) && Result;
   }
 
   // Return the usable size for a given chunk. Technically we lie, as we just
   // report the actual size of a chunk. This is done to counteract code actively
   // writing past the end of a chunk (like sqlite3) when the usable size allows
   // for it, which then forces realloc to copy the usable size of a chunk as
   // opposed to its actual size.
   uptr getUsableSize(const void *Ptr) {
if (!PrimaryT::SupportsMemoryTagging ||
       return;
 
     uptr UntaggedFaultAddr = untagPointer(FaultAddr);
     u8 FaultAddrTag = extractTag(FaultAddr);
     BlockInfo Info =
         PrimaryT::findNearestBlock(RegionInfoPtr, UntaggedFaultAddr);
 
     auto GetGranule = [&](uptr Addr, const char **Data, uint8_t *Tag) -> bool {
-      if (Addr < MemoryAddr ||
-          Addr + archMemoryTagGranuleSize() < Addr ||
+      if (Addr < MemoryAddr || Addr + archMemoryTagGranuleSize() < Addr ||
           Addr + archMemoryTagGranuleSize() > MemoryAddr + MemorySize)
         return false;
       *Data = &Memory[Addr - MemoryAddr];
       *Tag = static_cast<u8>(
           MemoryTags[(Addr - MemoryAddr) / archMemoryTagGranuleSize()]);
       return true;
     };
 
private:
   TSDRegistryT TSDRegistry;
   PrimaryT Primary;
   SecondaryT Secondary;
   QuarantineT Quarantine;
 
   u32 Cookie;
 
   struct {
-    u8 MayReturnNull : 1;       // may_return_null
+    u8 MayReturnNull : 1;              // may_return_null
     FillContentsMode FillContents : 2; // zero_contents, pattern_fill_contents
-    u8 DeallocTypeMismatch : 1; // dealloc_type_mismatch
-    u8 DeleteSizeMismatch : 1;  // delete_size_mismatch
+    u8 DeallocTypeMismatch : 1;        // dealloc_type_mismatch
+    u8 DeleteSizeMismatch : 1;         // delete_size_mismatch
     u8 TrackAllocationStacks : 1;
     u32 QuarantineMaxChunkSize; // quarantine_max_chunk_size
   } Options;
 
 #ifdef GWP_ASAN_HOOKS
   gwp_asan::GuardedPoolAllocator GuardedAlloc;
 #endif // GWP_ASAN_HOOKS
 

compiler-rt/lib/scudo/standalone/common.h

 
 struct BlockInfo {
   uptr BlockBegin;
   uptr BlockSize;
   uptr RegionBegin;
   uptr RegionEnd;
 };
 
+enum class Option : u8 {
+  ReleaseInterval,      // Release to OS interval in milliseconds.
+  MaxCacheEntriesCount, // Maximum number of blocks that can be cached.
+  MaxCacheEntrySize,    // Maximum size of a block that can be cached.
+};
+
 constexpr unsigned char PatternFillByte = 0xAB;
 
 enum FillContentsMode {
   NoFill = 0,
   ZeroFill = 1,
   PatternOrZeroFill = 2 // Pattern fill unless the memory is known to be
                         // zero-initialized already.
 };
 
 } // namespace scudo
 
 #endif // SCUDO_COMMON_H_

compiler-rt/lib/scudo/standalone/primary32.h

for (uptr I = 0; I < NumClasses; I++) {
       SizeClassInfo *Sci = getSizeClassInfo(I);
       Sci->RandState = getRandomU32(&Seed);
       // See comment in the 64-bit primary about releasing smaller size classes.
       Sci->CanRelease = (I != SizeClassMap::BatchClassId) &&
                         (getSizeByClassId(I) >= (PageSize / 32));
       if (Sci->CanRelease)
         Sci->ReleaseInfo.LastReleaseAtNs = Time;
     }
-    setReleaseToOsIntervalMs(ReleaseToOsInterval);
+    setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));
   }
   void init(s32 ReleaseToOsInterval) {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized(ReleaseToOsInterval);
   }
 
   void unmapTestOnly() {
     while (NumberOfStashedRegions > 0)
void getStats(ScopedString *Str) {
     }
     Str->append("Stats: SizeClassAllocator32: %zuM mapped in %zu allocations; "
                 "remains %zu\n",
                 TotalMapped >> 20, PoppedBlocks, PoppedBlocks - PushedBlocks);
     for (uptr I = 0; I < NumClasses; I++)
       getStats(Str, I, 0);
   }
 
-  void setReleaseToOsIntervalMs(s32 Interval) {
-    if (Interval >= MaxReleaseToOsIntervalMs) {
-      Interval = MaxReleaseToOsIntervalMs;
-    } else if (Interval <= MinReleaseToOsIntervalMs) {
-      Interval = MinReleaseToOsIntervalMs;
-    }
+  bool setOption(Option O, sptr Value) {
+    if (O == Option::ReleaseInterval) {
+      const s32 Interval =
+          Max(Min(static_cast<s32>(Value), MaxReleaseToOsIntervalMs),
+              MinReleaseToOsIntervalMs);
       atomic_store(&ReleaseToOsIntervalMs, Interval, memory_order_relaxed);
+      return true;
+    } else if (O == Option::MaxCacheEntriesCount ||
+               O == Option::MaxCacheEntrySize) {
+      // Not supported by the Primary, but not an error either.
+      return true;
+    }
+    return false;
   }
 
   uptr releaseToOS() {
     uptr TotalReleasedBytes = 0;
     for (uptr I = 0; I < NumClasses; I++) {
       SizeClassInfo *Sci = getSizeClassInfo(I);
       ScopedLock L(Sci->Mutex);
       TotalReleasedBytes += releaseToOSMaybe(Sci, I, /*Force=*/true);
void getStats(ScopedString *Str, uptr ClassId, uptr Rss) {
     const uptr AvailableChunks = Sci->AllocatedUser / getSizeByClassId(ClassId);
     Str->append("  %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
                 "inuse: %6zu avail: %6zu rss: %6zuK releases: %6zu\n",
                 ClassId, getSizeByClassId(ClassId), Sci->AllocatedUser >> 10,
                 Sci->Stats.PoppedBlocks, Sci->Stats.PushedBlocks, InUse,
                 AvailableChunks, Rss >> 10, Sci->ReleaseInfo.RangesReleased);
   }
 
-  s32 getReleaseToOsIntervalMs() {
-    return atomic_load(&ReleaseToOsIntervalMs, memory_order_relaxed);
-  }
-
   NOINLINE uptr releaseToOSMaybe(SizeClassInfo *Sci, uptr ClassId,
                                  bool Force = false) {
     const uptr BlockSize = getSizeByClassId(ClassId);
     const uptr PageSize = getPageSizeCached();
 
     CHECK_GE(Sci->Stats.PoppedBlocks, Sci->Stats.PushedBlocks);
     const uptr BytesInFreeList =
         Sci->AllocatedUser -
         (Sci->Stats.PoppedBlocks - Sci->Stats.PushedBlocks) * BlockSize;
     if (BytesInFreeList < PageSize)
       return 0; // No chance to release anything.
     const uptr BytesPushed =
         (Sci->Stats.PushedBlocks - Sci->ReleaseInfo.PushedBlocksAtLastRelease) *
         BlockSize;
     if (BytesPushed < PageSize)
       return 0; // Nothing new to release.
 
     if (!Force) {
-      const s32 IntervalMs = getReleaseToOsIntervalMs();
+      const s32 IntervalMs =
+          atomic_load(&ReleaseToOsIntervalMs, memory_order_relaxed);
       if (IntervalMs < 0)
         return 0;
       if (Sci->ReleaseInfo.LastReleaseAtNs +
               static_cast<u64>(IntervalMs) * 1000000 >
           getMonotonicTime()) {
         return 0; // Memory was returned recently.
       }
     }

compiler-rt/lib/scudo/standalone/primary64.h

for (uptr I = 0; I < NumClasses; I++) {
       // memory accesses which ends up being fairly costly. The current lower
       // limit is mostly arbitrary and based on empirical observations.
       // TODO(kostyak): make the lower limit a runtime option
       Region->CanRelease = (I != SizeClassMap::BatchClassId) &&
                            (getSizeByClassId(I) >= (PageSize / 32));
       if (Region->CanRelease)
         Region->ReleaseInfo.LastReleaseAtNs = Time;
     }
-    setReleaseToOsIntervalMs(ReleaseToOsInterval);
+    setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));
 
     if (SupportsMemoryTagging)
       UseMemoryTagging = systemSupportsMemoryTagging();
   }
   void init(s32 ReleaseToOsInterval) {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized(ReleaseToOsInterval);
   }
Str->append("Stats: SizeClassAllocator64: %zuM mapped (%zuM rss) in %zu "
                 "allocations; remains %zu\n",
                 TotalMapped >> 20, 0, PoppedBlocks,
                 PoppedBlocks - PushedBlocks);
 
     for (uptr I = 0; I < NumClasses; I++)
       getStats(Str, I, 0);
   }
 
-  void setReleaseToOsIntervalMs(s32 Interval) {
-    if (Interval >= MaxReleaseToOsIntervalMs) {
-      Interval = MaxReleaseToOsIntervalMs;
-    } else if (Interval <= MinReleaseToOsIntervalMs) {
-      Interval = MinReleaseToOsIntervalMs;
-    }
+  bool setOption(Option O, sptr Value) {
+    if (O == Option::ReleaseInterval) {
+      const s32 Interval =
+          Max(Min(static_cast<s32>(Value), MaxReleaseToOsIntervalMs),
+              MinReleaseToOsIntervalMs);
       atomic_store(&ReleaseToOsIntervalMs, Interval, memory_order_relaxed);
+      return true;
+    } else if (O == Option::MaxCacheEntriesCount ||
+               O == Option::MaxCacheEntrySize) {
+      // Not supported by the Primary, but not an error either.
+      return true;
+    }
+    return false;
   }
 
   uptr releaseToOS() {
     uptr TotalReleasedBytes = 0;
     for (uptr I = 0; I < NumClasses; I++) {
       RegionInfo *Region = getRegionInfo(I);
       ScopedLock L(Region->Mutex);
       TotalReleasedBytes += releaseToOSMaybe(Region, I, /*Force=*/true);
     }
     return TotalReleasedBytes;
   }
 
   bool useMemoryTagging() const {
     return SupportsMemoryTagging && UseMemoryTagging;
   }
   void disableMemoryTagging() { UseMemoryTagging = false; }
 
   const char *getRegionInfoArrayAddress() const {
     return reinterpret_cast<const char *>(RegionInfoArray);
   }
 
-  static uptr getRegionInfoArraySize() {
-    return sizeof(RegionInfoArray);
-  }
+  static uptr getRegionInfoArraySize() { return sizeof(RegionInfoArray); }
 
   static BlockInfo findNearestBlock(const char *RegionInfoData, uptr Ptr) {
     const RegionInfo *RegionInfoArray =
         reinterpret_cast<const RegionInfo *>(RegionInfoData);
     uptr ClassId;
     uptr MinDistance = -1UL;
     for (uptr I = 0; I != NumClasses; ++I) {
       if (I == SizeClassMap::BatchClassId)
Str->append("%s %02zu (%6zu): mapped: %6zuK popped: %7zu pushed: %7zu "
                 Region->Exhausted ? "F" : " ", ClassId,
                 getSizeByClassId(ClassId), Region->MappedUser >> 10,
                 Region->Stats.PoppedBlocks, Region->Stats.PushedBlocks, InUse,
                 TotalChunks, Rss >> 10, Region->ReleaseInfo.RangesReleased,
                 Region->ReleaseInfo.LastReleasedBytes >> 10, Region->RegionBeg,
                 getRegionBaseByClassId(ClassId));
   }
 
-  s32 getReleaseToOsIntervalMs() {
-    return atomic_load(&ReleaseToOsIntervalMs, memory_order_relaxed);
-  }
-
   NOINLINE uptr releaseToOSMaybe(RegionInfo *Region, uptr ClassId,
                                  bool Force = false) {
     const uptr BlockSize = getSizeByClassId(ClassId);
     const uptr PageSize = getPageSizeCached();
 
     CHECK_GE(Region->Stats.PoppedBlocks, Region->Stats.PushedBlocks);
     const uptr BytesInFreeList =
         Region->AllocatedUser -
         (Region->Stats.PoppedBlocks - Region->Stats.PushedBlocks) * BlockSize;
     if (BytesInFreeList < PageSize)
       return 0; // No chance to release anything.
     const uptr BytesPushed = (Region->Stats.PushedBlocks -
                               Region->ReleaseInfo.PushedBlocksAtLastRelease) *
                              BlockSize;
     if (BytesPushed < PageSize)
       return 0; // Nothing new to release.
 
     if (!Force) {
-      const s32 IntervalMs = getReleaseToOsIntervalMs();
+      const s32 IntervalMs =
+          atomic_load(&ReleaseToOsIntervalMs, memory_order_relaxed);
       if (IntervalMs < 0)
         return 0;
       if (Region->ReleaseInfo.LastReleaseAtNs +
               static_cast<u64>(IntervalMs) * 1000000 >
           getMonotonicTime()) {
         return 0; // Memory was returned recently.
       }
     }

compiler-rt/lib/scudo/standalone/secondary.h

 class MapAllocatorNoCache {
 public:
   void initLinkerInitialized(UNUSED s32 ReleaseToOsInterval) {}
   void init(UNUSED s32 ReleaseToOsInterval) {}
   bool retrieve(UNUSED uptr Size, UNUSED LargeBlock::Header **H) {
     return false;
   }
   bool store(UNUSED LargeBlock::Header *H) { return false; }
-  static bool canCache(UNUSED uptr Size) { return false; }
+  bool canCache(UNUSED uptr Size) { return false; }
   void disable() {}
   void enable() {}
   void releaseToOS() {}
-  void setReleaseToOsIntervalMs(UNUSED s32 Interval) {}
+  bool setOption(UNUSED Option O, UNUSED sptr Value) { return false; }
 };
 
-template <uptr MaxEntriesCount = 32U, uptr MaxEntrySize = 1UL << 19,
+template <u32 EntriesArraySize = 32U, u32 DefaultMaxEntriesCount = 32U,
+          uptr DefaultMaxEntrySize = 1UL << 19,
           s32 MinReleaseToOsIntervalMs = INT32_MIN,
           s32 MaxReleaseToOsIntervalMs = INT32_MAX>
 class MapAllocatorCache {
 public:
   // Fuchsia doesn't allow releasing Secondary blocks yet. Note that 0 length
   // arrays are an extension for some compilers.
   // FIXME(kostyak): support (partially) the cache on Fuchsia.
-  static_assert(!SCUDO_FUCHSIA || MaxEntriesCount == 0U, "");
+  static_assert(!SCUDO_FUCHSIA || EntriesArraySize == 0U, "");
+
+  // Ensure the default maximum specified fits the array.
+  static_assert(DefaultMaxEntriesCount <= EntriesArraySize, "");
 
   void initLinkerInitialized(s32 ReleaseToOsInterval) {
-    setReleaseToOsIntervalMs(ReleaseToOsInterval);
+    setOption(Option::MaxCacheEntriesCount,
+              static_cast<sptr>(DefaultMaxEntriesCount));
+    setOption(Option::MaxCacheEntrySize,
+              static_cast<sptr>(DefaultMaxEntrySize));
+    setOption(Option::ReleaseInterval, static_cast<sptr>(ReleaseToOsInterval));
   }
   void init(s32 ReleaseToOsInterval) {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized(ReleaseToOsInterval);
   }
 
   bool store(LargeBlock::Header *H) {
     bool EntryCached = false;
     bool EmptyCache = false;
     const u64 Time = getMonotonicTime();
+    const u32 MaxCount = atomic_load(&MaxEntriesCount, memory_order_relaxed);
     {
       ScopedLock L(Mutex);
-      if (EntriesCount == MaxEntriesCount) {
+      if (EntriesCount >= MaxCount) {
         if (IsFullEvents++ == 4U)
           EmptyCache = true;
       } else {
-        for (uptr I = 0; I < MaxEntriesCount; I++) {
+        for (u32 I = 0; I < MaxCount; I++) {
           if (Entries[I].Block)
             continue;
           if (I != 0)
             Entries[I] = Entries[0];
           Entries[0].Block = reinterpret_cast<uptr>(H);
           Entries[0].BlockEnd = H->BlockEnd;
           Entries[0].MapBase = H->MapBase;
           Entries[0].MapSize = H->MapSize;
           Entries[0].Data = H->Data;
           Entries[0].Time = Time;
           EntriesCount++;
           EntryCached = true;
           break;
         }
       }
     }
     s32 Interval;
     if (EmptyCache)
       empty();
-    else if ((Interval = getReleaseToOsIntervalMs()) >= 0)
+    else if ((Interval = atomic_load(&ReleaseToOsIntervalMs,
+                                     memory_order_relaxed)) >= 0)
       releaseOlderThan(Time - static_cast<u64>(Interval) * 1000000);
     return EntryCached;
   }
 
   bool retrieve(uptr Size, LargeBlock::Header **H) {
     const uptr PageSize = getPageSizeCached();
+    const u32 MaxCount = atomic_load(&MaxEntriesCount, memory_order_relaxed);
     ScopedLock L(Mutex);
     if (EntriesCount == 0)
       return false;
-    for (uptr I = 0; I < MaxEntriesCount; I++) {
+    for (u32 I = 0; I < MaxCount; I++) {
       if (!Entries[I].Block)
         continue;
       const uptr BlockSize = Entries[I].BlockEnd - Entries[I].Block;
       if (Size > BlockSize)
         continue;
       if (Size < BlockSize - PageSize * 4U)
         continue;
       *H = reinterpret_cast<LargeBlock::Header *>(Entries[I].Block);
       Entries[I].Block = 0;
       (*H)->BlockEnd = Entries[I].BlockEnd;
       (*H)->MapBase = Entries[I].MapBase;
       (*H)->MapSize = Entries[I].MapSize;
       (*H)->Data = Entries[I].Data;
       EntriesCount--;
       return true;
     }
     return false;
   }
 
-  static bool canCache(uptr Size) {
-    return MaxEntriesCount != 0U && Size <= MaxEntrySize;
+  bool canCache(uptr Size) {
+    return atomic_load(&MaxEntriesCount, memory_order_relaxed) != 0U &&
+           Size <= atomic_load(&MaxEntrySize, memory_order_relaxed);
   }
 
-  void setReleaseToOsIntervalMs(s32 Interval) {
-    if (Interval >= MaxReleaseToOsIntervalMs) {
-      Interval = MaxReleaseToOsIntervalMs;
-    } else if (Interval <= MinReleaseToOsIntervalMs) {
-      Interval = MinReleaseToOsIntervalMs;
-    }
+  bool setOption(Option O, sptr Value) {
+    if (O == Option::ReleaseInterval) {
+      const s32 Interval =
+          Max(Min(static_cast<s32>(Value), MaxReleaseToOsIntervalMs),
+              MinReleaseToOsIntervalMs);
       atomic_store(&ReleaseToOsIntervalMs, Interval, memory_order_relaxed);
+      return true;
+    } else if (O == Option::MaxCacheEntriesCount) {
+      const u32 MaxCount = static_cast<u32>(Value);
+      if (MaxCount > EntriesArraySize)
+        return false;
+      atomic_store(&MaxEntriesCount, MaxCount, memory_order_relaxed);
+      return true;
+    } else if (O == Option::MaxCacheEntrySize) {
+      atomic_store(&MaxEntrySize, static_cast<uptr>(Value),
+                   memory_order_relaxed);
+      return true;
+    }
+    return false;
   }
 
   void releaseToOS() { releaseOlderThan(UINT64_MAX); }
 
   void disable() { Mutex.lock(); }
 
   void enable() { Mutex.unlock(); }
 
 private:
   void empty() {
     struct {
       void *MapBase;
       uptr MapSize;
       MapPlatformData Data;
-    } MapInfo[MaxEntriesCount];
+    } MapInfo[EntriesArraySize];
     uptr N = 0;
     {
       ScopedLock L(Mutex);
-      for (uptr I = 0; I < MaxEntriesCount; I++) {
+      for (uptr I = 0; I < EntriesArraySize; I++) {
         if (!Entries[I].Block)
           continue;
         MapInfo[N].MapBase = reinterpret_cast<void *>(Entries[I].MapBase);
         MapInfo[N].MapSize = Entries[I].MapSize;
         MapInfo[N].Data = Entries[I].Data;
         Entries[I].Block = 0;
         N++;
       }
       EntriesCount = 0;
       IsFullEvents = 0;
     }
     for (uptr I = 0; I < N; I++)
       unmap(MapInfo[I].MapBase, MapInfo[I].MapSize, UNMAP_ALL,
             &MapInfo[I].Data);
   }
 
   void releaseOlderThan(u64 Time) {
     ScopedLock L(Mutex);
     if (!EntriesCount)
       return;
-    for (uptr I = 0; I < MaxEntriesCount; I++) {
+    for (uptr I = 0; I < EntriesArraySize; I++) {
       if (!Entries[I].Block || !Entries[I].Time || Entries[I].Time > Time)
         continue;
       releasePagesToOS(Entries[I].Block, 0,
                        Entries[I].BlockEnd - Entries[I].Block,
                        &Entries[I].Data);
       Entries[I].Time = 0;
     }
   }
 
-  s32 getReleaseToOsIntervalMs() {
-    return atomic_load(&ReleaseToOsIntervalMs, memory_order_relaxed);
-  }
-
   struct CachedBlock {
     uptr Block;
     uptr BlockEnd;
     uptr MapBase;
     uptr MapSize;
     MapPlatformData Data;
     u64 Time;
   };
 
   HybridMutex Mutex;
-  CachedBlock Entries[MaxEntriesCount];
+  CachedBlock Entries[EntriesArraySize];
   u32 EntriesCount;
+  atomic_u32 MaxEntriesCount;
+  atomic_uptr MaxEntrySize;
   uptr LargestSize;
   u32 IsFullEvents;
   atomic_s32 ReleaseToOsIntervalMs;
 };
 
 template <class CacheT> class MapAllocator {
 public:
   void initLinkerInitialized(GlobalStats *S, s32 ReleaseToOsInterval = -1) {
void enable() {
     Mutex.unlock();
   }
 
   template <typename F> void iterateOverBlocks(F Callback) const {
     for (const auto &H : InUseBlocks)
       Callback(reinterpret_cast<uptr>(&H) + LargeBlock::getHeaderSize());
   }
 
-  static uptr canCache(uptr Size) { return CacheT::canCache(Size); }
+  uptr canCache(uptr Size) { return Cache.canCache(Size); }
 
-  void setReleaseToOsIntervalMs(s32 Interval) {
-    Cache.setReleaseToOsIntervalMs(Interval);
-  }
+  bool setOption(Option O, sptr Value) { return Cache.setOption(O, Value); }
 
   void releaseToOS() { Cache.releaseToOS(); }
 
 private:
   CacheT Cache;
 
   HybridMutex Mutex;
   DoublyLinkedList<LargeBlock::Header> InUseBlocks;

 void *MapAllocator<CacheT>::allocate(uptr Size, uptr AlignmentHint,
                                      uptr *BlockEnd,
                                      FillContentsMode FillContents) {
   DCHECK_GE(Size, AlignmentHint);
   const uptr PageSize = getPageSizeCached();
   const uptr RoundedSize =
       roundUpTo(Size + LargeBlock::getHeaderSize(), PageSize);
 
-  if (AlignmentHint < PageSize && CacheT::canCache(RoundedSize)) {
+  if (AlignmentHint < PageSize && Cache.canCache(RoundedSize)) {
     LargeBlock::Header *H;
     if (Cache.retrieve(RoundedSize, &H)) {
       if (BlockEnd)
         *BlockEnd = H->BlockEnd;
       void *Ptr = reinterpret_cast<void *>(reinterpret_cast<uptr>(H) +
                                            LargeBlock::getHeaderSize());
       if (FillContents)
         memset(Ptr, FillContents == ZeroFill ? 0 : PatternFillByte,
template <class CacheT> void MapAllocator<CacheT>::deallocate(void *Ptr) {
   {
     ScopedLock L(Mutex);
     InUseBlocks.remove(H);
     FreedBytes += CommitSize;
     NumberOfFrees++;
     Stats.sub(StatAllocated, CommitSize);
     Stats.sub(StatMapped, H->MapSize);
   }
-  if (CacheT::canCache(CommitSize) && Cache.store(H))
+  if (Cache.canCache(CommitSize) && Cache.store(H))
     return;
   void *Addr = reinterpret_cast<void *>(H->MapBase);
   const uptr Size = H->MapSize;
   MapPlatformData Data = H->Data;
   unmap(Addr, Size, UNMAP_ALL, &Data);
 }
 
 template <class CacheT>

compiler-rt/lib/scudo/standalone/tests/secondary_test.cpp

 #include <mutex>
 #include <random>
 #include <thread>
 #include <vector>
 
 template <class SecondaryT> static void testSecondaryBasic(void) {
   scudo::GlobalStats S;
   S.init();
-  SecondaryT *L = new SecondaryT;
+  std::unique_ptr<SecondaryT> L(new SecondaryT);
   L->init(&S);
   const scudo::uptr Size = 1U << 16;
   void *P = L->allocate(Size);
   EXPECT_NE(P, nullptr);
   memset(P, 'A', Size);
   EXPECT_GE(SecondaryT::getBlockSize(P), Size);
   L->deallocate(P);
   // If the Secondary can't cache that pointer, it will be unmapped.
-  if (!SecondaryT::canCache(Size))
+  if (!L->canCache(Size))
     EXPECT_DEATH(memset(P, 'A', Size), "");
 
   const scudo::uptr Align = 1U << 16;
   P = L->allocate(Size + Align, Align);
   EXPECT_NE(P, nullptr);
   void *AlignedP = reinterpret_cast<void *>(
       scudo::roundUpTo(reinterpret_cast<scudo::uptr>(P), Align));
   memset(AlignedP, 'A', Size);
template <class SecondaryT> static void testSecondaryBasic(void) {
   Str.output();
 }
 
 TEST(ScudoSecondaryTest, SecondaryBasic) {
   testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorNoCache>>();
 #if !SCUDO_FUCHSIA
   testSecondaryBasic<scudo::MapAllocator<scudo::MapAllocatorCache<>>>();
   testSecondaryBasic<
-      scudo::MapAllocator<scudo::MapAllocatorCache<64U, 1UL << 20>>>();
+      scudo::MapAllocator<scudo::MapAllocatorCache<128U, 64U, 1UL << 20>>>();
 #endif
 }
 
 #if SCUDO_FUCHSIA
 using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorNoCache>;
 #else
 using LargeAllocator = scudo::MapAllocator<scudo::MapAllocatorCache<>>;
 #endif
 
 // This exercises a variety of combinations of size and alignment for the
 // MapAllocator. The size computation done here mimic the ones done by the
 // combined allocator.
 TEST(ScudoSecondaryTest, SecondaryCombinations) {
   constexpr scudo::uptr MinAlign = FIRST_32_SECOND_64(8, 16);
   constexpr scudo::uptr HeaderSize = scudo::roundUpTo(8, MinAlign);
-  LargeAllocator *L = new LargeAllocator;
+  std::unique_ptr<LargeAllocator> L(new LargeAllocator);
   L->init(nullptr);
   for (scudo::uptr SizeLog = 0; SizeLog <= 20; SizeLog++) {
     for (scudo::uptr AlignLog = FIRST_32_SECOND_64(3, 4); AlignLog <= 16;
          AlignLog++) {
       const scudo::uptr Align = 1U << AlignLog;
       for (scudo::sptr Delta = -128; Delta <= 128; Delta += 8) {
         if (static_cast<scudo::sptr>(1U << SizeLog) + Delta <= 0)
           continue;
for (scudo::uptr SizeLog = 0; SizeLog <= 20; SizeLog++) {
     }
   }
   scudo::ScopedString Str(1024);
   L->getStats(&Str);
   Str.output();
 }
 
 TEST(ScudoSecondaryTest, SecondaryIterate) {
-  LargeAllocator *L = new LargeAllocator;
+  std::unique_ptr<LargeAllocator> L(new LargeAllocator);
   L->init(nullptr);
   std::vector<void *> V;
   const scudo::uptr PageSize = scudo::getPageSizeCached();
   for (scudo::uptr I = 0; I < 32U; I++)
     V.push_back(L->allocate((std::rand() % 16) * PageSize));
   auto Lambda = [V](scudo::uptr Block) {
     EXPECT_NE(std::find(V.begin(), V.end(), reinterpret_cast<void *>(Block)),
               V.end());
   };
   L->disable();
   L->iterateOverBlocks(Lambda);
   L->enable();
   while (!V.empty()) {
     L->deallocate(V.back());
     V.pop_back();
   }
   scudo::ScopedString Str(1024);
   L->getStats(&Str);
   Str.output();
 }
 
+#if !SCUDO_FUCHSIA
+TEST(ScudoSecondaryTest, SecondaryOptions) {
+  std::unique_ptr<LargeAllocator> L(new LargeAllocator);
+  L->init(nullptr);
+  // Attempt to set a maximum number of entries higher than the array size.
+  EXPECT_FALSE(L->setOption(scudo::Option::MaxCacheEntriesCount, 4096U));
+  // A negative number will be cast to a scudo::u32, and fail.
+  EXPECT_FALSE(L->setOption(scudo::Option::MaxCacheEntriesCount, -1));
+  // Various valid combinations.
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntriesCount, 4U));
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntrySize, 1UL << 20));
+  EXPECT_TRUE(L->canCache(1UL << 18));
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntrySize, 1UL << 17));
+  EXPECT_FALSE(L->canCache(1UL << 18));
+  EXPECT_TRUE(L->canCache(1UL << 16));
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntriesCount, 0U));
+  EXPECT_FALSE(L->canCache(1UL << 16));
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntriesCount, 4U));
+  EXPECT_TRUE(L->setOption(scudo::Option::MaxCacheEntrySize, 1UL << 20));
+  EXPECT_TRUE(L->canCache(1UL << 16));
+}
+#endif
+
 static std::mutex Mutex;
 static std::condition_variable Cv;
 static bool Ready = false;
 
 static void performAllocations(LargeAllocator *L) {
   std::vector<void *> V;
   const scudo::uptr PageSize = scudo::getPageSizeCached();
   {
static void performAllocations(LargeAllocator *L) {
   }
   while (!V.empty()) {
     L->deallocate(V.back());
     V.pop_back();
   }
 }
 
 TEST(ScudoSecondaryTest, SecondaryThreadsRace) {
-  LargeAllocator *L = new LargeAllocator;
+  std::unique_ptr<LargeAllocator> L(new LargeAllocator);
   L->init(nullptr, /*ReleaseToOsInterval=*/0);
   std::thread Threads[16];
   for (scudo::uptr I = 0; I < ARRAY_SIZE(Threads); I++)
-    Threads[I] = std::thread(performAllocations, L);
+    Threads[I] = std::thread(performAllocations, L.get());
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     Ready = true;
     Cv.notify_all();
   }
   for (auto &T : Threads)
     T.join();
   scudo::ScopedString Str(1024);
   L->getStats(&Str);
   Str.output();
 }

compiler-rt/lib/scudo/standalone/wrappers_c.h

 #ifndef M_DECAY_TIME
 #define M_DECAY_TIME -100
 #endif
 
 #ifndef M_PURGE
 #define M_PURGE -101
 #endif
 
+#ifndef M_CACHE_COUNT_MAX
+#define M_CACHE_COUNT_MAX -200
+#endif
+
+#ifndef M_CACHE_SIZE_MAX
+#define M_CACHE_SIZE_MAX -201
+#endif
+
 #endif // SCUDO_WRAPPERS_C_H_

compiler-rt/lib/scudo/standalone/wrappers_c.inc

 //===-- wrappers_c.inc ------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SCUDO_PREFIX
 #error "Define SCUDO_PREFIX prior to including this file!"
 #endif
 
 // malloc-type functions have to be aligned to std::max_align_t. This is
 // distinct from (1U << SCUDO_MIN_ALIGNMENT_LOG), since C++ new-type functions
 // do not have to abide by the same requirement.
 #ifndef SCUDO_MALLOC_ALIGNMENT
 #define SCUDO_MALLOC_ALIGNMENT FIRST_32_SECOND_64(8U, 16U)
 #endif
 
 extern "C" {
 
 INTERFACE WEAK void *SCUDO_PREFIX(calloc)(size_t nmemb, size_t size) {
   scudo::uptr Product;
   if (UNLIKELY(scudo::checkForCallocOverflow(size, nmemb, &Product))) {
     if (SCUDO_ALLOCATOR.canReturnNull()) {
       errno = ENOMEM;
       return nullptr;
     }
     scudo::reportCallocOverflow(nmemb, size);
   }
   return scudo::setErrnoOnNull(SCUDO_ALLOCATOR.allocate(
       Product, scudo::Chunk::Origin::Malloc, SCUDO_MALLOC_ALIGNMENT, true));
 }
 
 INTERFACE WEAK void SCUDO_PREFIX(free)(void *ptr) {
   SCUDO_ALLOCATOR.deallocate(ptr, scudo::Chunk::Origin::Malloc);
 }
 
 INTERFACE WEAK struct SCUDO_MALLINFO SCUDO_PREFIX(mallinfo)(void) {

 }
 
 void SCUDO_PREFIX(malloc_postinit)() {
   SCUDO_ALLOCATOR.initGwpAsan();
   pthread_atfork(SCUDO_PREFIX(malloc_disable), SCUDO_PREFIX(malloc_enable),
                  SCUDO_PREFIX(malloc_enable));
 }
 
-INTERFACE WEAK int SCUDO_PREFIX(mallopt)(int param, UNUSED int value) {
+INTERFACE WEAK int SCUDO_PREFIX(mallopt)(int param, int value) {
+  bool Success = false;
   if (param == M_DECAY_TIME) {
     if (SCUDO_ANDROID) {
-      if (value == 0) {
-        // Will set the release values to their minimum values.
-        value = INT32_MIN;
-      } else {
-        // Will set the release values to their maximum values.
-        value = INT32_MAX;
-      }
+      // Android only uses 0 and 1.
+      // 0 sets the releases value to their minimum, 1 to their maximum.
+      value = (value == 0) ? INT32_MIN : INT32_MAX;
     }
-
-    SCUDO_ALLOCATOR.setOption(scudo::Option::ReleaseInterval,
+    Success = SCUDO_ALLOCATOR.setOption(scudo::Option::ReleaseInterval,
                                         static_cast<scudo::sptr>(value));
-    return 1;
   } else if (param == M_PURGE) {
     SCUDO_ALLOCATOR.releaseToOS();
-    return 1;
+    Success = true;
+  } else if (param == M_CACHE_COUNT_MAX) {
+    Success = SCUDO_ALLOCATOR.setOption(scudo::Option::MaxCacheEntriesCount,
+                                        static_cast<scudo::sptr>(value));
+  } else if (param == M_CACHE_SIZE_MAX) {
+    Success = SCUDO_ALLOCATOR.setOption(scudo::Option::MaxCacheEntrySize,
+                                        static_cast<scudo::sptr>(value));
   }
-  return 0;
+  return Success ? 1 : 0;
 }
 
 INTERFACE WEAK void *SCUDO_PREFIX(aligned_alloc)(size_t alignment,
                                                  size_t size) {
   if (UNLIKELY(scudo::checkAlignedAllocAlignmentAndSize(alignment, size))) {
     if (SCUDO_ALLOCATOR.canReturnNull()) {
       errno = EINVAL;
       return nullptr;