[scudo][standalone] mallopt runtime configuration options

[cryptoad]

Summary

Partners have requested the ability to configure more parts of Scudo
at runtime, notably the Secondary cache options (maximum number of
blocks cached, maximum size) as well as the TSD registry options
(the maximum number of TSDs in use).

This CL adds a few more Scudo specific mallopt parameters that are
passed down to the various subcomponents of the Combined allocator.

• M_CACHE_COUNT_MAX: sets the maximum number of Secondary cached items
• M_CACHE_SIZE_MAX: sets the maximum size of a cacheable item in the Secondary
• M_TSDS_COUNT_MAX: sets the maximum number of TSDs that can be used (Shared Registry only)

Regarding the TSDs maximum count, this is a one way option, only
allowing to increase the count.

In order to allow for this, I rearranged the code to have some setOption
member function to the relevant classes, using the scudo::Option class
enum to determine what is to be set.

This also fixes an issue where a static variable (Ready) was used in
templated functions without being set back to false every time.

[cferris]

Is there any major changes from the other mallopt change? In other words, should I rerun performance data?

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

68

Super small nit, but I think this means default 1 TSD, max of 2 TSDs. So the comment should be max 2 TSDs.

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

710

Is the compiler required to call setOptions if Result is false? Since the whole statement would be false, I think there is a chance a good enough compiler might not even make these calls if it notices that the first result or second result is false.

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

186

Small nit, should this align with the comments down below. Also, should MemtagTuning have a short explanation.

[cryptoad]

Addressing Chrisopher's comments:

• fixed a couple of comments
• reworked setOption to avoid short circuiting

[cryptoad]

In D84667#2176494, @cferris wrote:

Is there any major changes from the other mallopt change? In other words, should I rerun performance data?

This is the same as the previous one, except for a couple of LIKELY/UNLIKELY in combined.h, which I can actually remove and save for a later CL.

[cferris]

Okay, then this all looks good to me, and the previous perf results (that showed no perf difference) should carry over.

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<256U, 32U, 2UL << 20, 0, 1000>>
+      Secondary;
   template <class A>
-  using TSDRegistryT = TSDRegistrySharedT<A, 2U>; // Shared, max 2 TSDs.
+  using TSDRegistryT = TSDRegistrySharedT<A, 8U, 2U>; // Shared, max 8 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.
+  using TSDRegistryT = TSDRegistrySharedT<A, 2U, 1U>; // Shared, max 2 TSDs.
 };
 
 #if SCUDO_CAN_USE_PRIMARY64
 struct FuchsiaConfig {
   // 1GB Regions
   typedef SizeClassAllocator64<DefaultSizeClassMap, 30U> Primary;
   typedef MapAllocator<MapAllocatorNoCache> Secondary;
   template <class A>
-  using TSDRegistryT = TSDRegistrySharedT<A, 8U>; // Shared, max 8 TSDs.
+  using TSDRegistryT = TSDRegistrySharedT<A, 8U, 4U>; // Shared, max 8 TSDs.
 };
 #endif
 
 #if SCUDO_ANDROID
 typedef AndroidConfig Config;
 #elif SCUDO_FUCHSIA
 typedef FuchsiaConfig Config;
 #else
 typedef DefaultConfig Config;
 #endif
 
 } // namespace scudo
 
 #endif // SCUDO_ALLOCATOR_CONFIG_H_

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, MemtagTuning };
-
 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;
 

 
 #ifdef GWP_ASAN_HOOKS
     if (UNLIKELY(GuardedAlloc.shouldSample())) {
       if (void *Ptr = GuardedAlloc.allocate(roundUpTo(Size, Alignment)))
         return Ptr;
     }
 #endif // GWP_ASAN_HOOKS
 
-    FillContentsMode FillContents =
+    const FillContentsMode FillContents =
         ZeroContents ? ZeroFill : Options.FillContents;
 
     if (UNLIKELY(Alignment > MaxAlignment)) {
       if (Options.MayReturnNull)
         return nullptr;
       reportAlignmentTooBig(Alignment, MaxAlignment);
     }
-    if (Alignment < MinAlignment)
+    if (UNLIKELY(Alignment < MinAlignment))
       Alignment = MinAlignment;
 
     // If the requested size happens to be 0 (more common than you might think),
     // allocate MinAlignment bytes on top of the header. Then add the extra
     // bytes required to fulfill the alignment requirements: we allocate enough
     // to be sure that there will be an address in the block that will satisfy
     // the alignment.
     const uptr NeededSize =
if (LIKELY(PrimaryT::canAllocate(NeededSize))) {
       Block = TSD->Cache.allocate(ClassId);
       // If the allocation failed, the most likely reason with a 32-bit primary
       // is the region being full. In that event, retry in each successively
       // larger class until it fits. If it fails to fit in the largest class,
       // fallback to the Secondary.
       if (UNLIKELY(!Block)) {
         while (ClassId < SizeClassMap::LargestClassId) {
           Block = TSD->Cache.allocate(++ClassId);
-          if (LIKELY(Block)) {
+          if (LIKELY(Block))
             break;
-          }
-        }
-        if (UNLIKELY(!Block)) {
+        if (UNLIKELY(!Block))
           ClassId = 0;
-        }
-      }
       if (UnlockRequired)
         TSD->unlock();
     }
     if (UNLIKELY(ClassId == 0))
       Block = Secondary.allocate(NeededSize, Alignment, &SecondaryBlockEnd,
                                  FillContents);
 
     if (UNLIKELY(!Block)) {
       if (Options.MayReturnNull)
         return nullptr;
       reportOutOfMemory(NeededSize);
     }
 
     const uptr BlockUptr = reinterpret_cast<uptr>(Block);
     const uptr UnalignedUserPtr = BlockUptr + Chunk::getHeaderSize();
     const uptr UserPtr = roundUpTo(UnalignedUserPtr, Alignment);
 
     void *Ptr = reinterpret_cast<void *>(UserPtr);
     void *TaggedPtr = Ptr;
-    if (ClassId) {
+    if (LIKELY(ClassId)) {
       // We only need to zero or tag the contents for Primary backed
       // allocations. We only set tags for primary allocations in order to avoid
       // faulting potentially large numbers of pages for large secondary
       // allocations. We assume that guard pages are enough to protect these
       // allocations.
       //
       // FIXME: When the kernel provides a way to set the background tag of a
       // mapping, we should be able to tag secondary allocations as well.
#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;
-    }
+    initThreadMaybe();
     if (O == Option::MemtagTuning) {
       // Enabling odd/even tags involves a tradeoff between use-after-free
       // detection and buffer overflow detection. Odd/even tags make it more
       // likely for buffer overflows to be detected by increasing the size of
       // the guaranteed "red zone" around the allocation, but on the other hand
       // use-after-free is less likely to be detected because the tag space for
       // any particular chunk is cut in half. Therefore we use this tuning
       // setting to control whether odd/even tags are enabled.
-      if (Value == M_MEMTAG_TUNING_BUFFER_OVERFLOW) {
+      if (Value == M_MEMTAG_TUNING_BUFFER_OVERFLOW)
         Options.UseOddEvenTags = true;
-        return true;
-      }
-      if (Value == M_MEMTAG_TUNING_UAF) {
+      else if (Value == M_MEMTAG_TUNING_UAF)
         Options.UseOddEvenTags = false;
-        return true;
-      }
+    } else {
+      // We leave it to the various sub-components to decide whether or not they
+      // want to handle the option, but we do not want to short-circuit
+      // execution if one of the setOption was to return false.
+      const bool PrimaryResult = Primary.setOption(O, Value);
+      const bool SecondaryResult = Secondary.setOption(O, Value);
+      const bool RegistryResult = TSDRegistry.setOption(O, Value);
+      return PrimaryResult && SecondaryResult && RegistryResult;
     }
     return false;
   }
 
   // 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
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;
     u8 UseOddEvenTags : 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.
+  MemtagTuning,         // Whether to tune tagging for UAF or overflow.
+  MaxCacheEntriesCount, // Maximum number of blocks that can be cached.
+  MaxCacheEntrySize,    // Maximum size of a block that can be cached.
+  MaxTSDsCount,         // Number of usable TSDs for the shared registry.
+};
+
 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/include/scudo/interface.h

 
 // Tune the allocator's choice of memory tags to make it more likely that
 // a certain class of memory errors will be detected. The value argument should
 // be one of the enumerators of the scudo_memtag_tuning enum below.
 #ifndef M_MEMTAG_TUNING
 #define M_MEMTAG_TUNING -102
 #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
+
+#ifndef M_TSDS_COUNT_MAX
+#define M_TSDS_COUNT_MAX -202
+#endif
+
 enum scudo_memtag_tuning {
   // Tune for buffer overflows.
   M_MEMTAG_TUNING_BUFFER_OVERFLOW,
 
   // Tune for use-after-free.
   M_MEMTAG_TUNING_UAF,
 };
 
 } // extern "C"
 
 #endif // SCUDO_INTERFACE_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;
+    }
+    // Not supported by the Primary, but not an error either.
+    return true;
   }
 
   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 -
if (BlockSize < PageSize / 16U) {
         return 0;
       // We want 8x% to 9x% free bytes (the larger the bock, the lower the %).
       if ((BytesInFreeList * 100U) / Sci->AllocatedUser <
           (100U - 1U - BlockSize / 16U))
         return 0;
     }
 
     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;
+    }
+    // Not supported by the Primary, but not an error either.
+    return true;
   }
 
   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);
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 -
if (BlockSize < PageSize / 16U) {
         return 0;
       // We want 8x% to 9x% free bytes (the larger the bock, the lower the %).
       if ((BytesInFreeList * 100U) / Region->AllocatedUser <
           (100U - 1U - BlockSize / 16U))
         return 0;
     }
 
     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(Option O, UNUSED sptr Value) {
+    if (O == Option::ReleaseInterval || O == Option::MaxCacheEntriesCount ||
+        O == Option::MaxCacheEntrySize)
+      return false;
+    // Not supported by the Secondary Cache, but not an error either.
+    return true;
+  }
 };
 
-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;
+    }
+    // Not supported by the Secondary Cache, but not an error either.
+    return true;
   }
 
   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/combined_test.cpp

 #include <condition_variable>
 #include <memory>
 #include <mutex>
 #include <thread>
 #include <vector>
 
 static std::mutex Mutex;
 static std::condition_variable Cv;
-static bool Ready = false;
+static bool Ready;
 
 static constexpr scudo::Chunk::Origin Origin = scudo::Chunk::Origin::Malloc;
 
 static void disableDebuggerdMaybe() {
 #if SCUDO_ANDROID
   // Disable the debuggerd signal handler on Android, without this we can end
   // up spending a significant amount of time creating tombstones.
   signal(SIGSEGV, SIG_DFL);
template <typename AllocatorT> static void stressAllocator(AllocatorT *A) {
   while (!V.empty()) {
     auto Pair = V.back();
     A->deallocate(Pair.first, Origin, Pair.second);
     V.pop_back();
   }
 }
 
 template <class Config> static void testAllocatorThreaded() {
+  Ready = false;
   using AllocatorT = TestAllocator<Config>;
   auto Allocator = std::unique_ptr<AllocatorT>(new AllocatorT());
   std::thread Threads[32];
   for (scudo::uptr I = 0; I < ARRAY_SIZE(Threads); I++)
     Threads[I] = std::thread(stressAllocator<AllocatorT>, Allocator.get());
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     Ready = true;

 
 static const scudo::uptr DeathRegionSizeLog = 20U;
 struct DeathConfig {
   // Tiny allocator, its Primary only serves chunks of four sizes.
   using DeathSizeClassMap = scudo::FixedSizeClassMap<DeathSizeClassConfig>;
   typedef scudo::SizeClassAllocator64<DeathSizeClassMap, DeathRegionSizeLog>
       Primary;
   typedef scudo::MapAllocator<scudo::MapAllocatorNoCache> Secondary;
-  template <class A> using TSDRegistryT = scudo::TSDRegistrySharedT<A, 1U>;
+  template <class A> using TSDRegistryT = scudo::TSDRegistrySharedT<A, 1U, 1U>;
 };
 
 TEST(ScudoCombinedTest, DeathCombined) {
   using AllocatorT = TestAllocator<DeathConfig>;
   auto Allocator = std::unique_ptr<AllocatorT>(new AllocatorT());
 
   const scudo::uptr Size = 1000U;
   void *P = Allocator->allocate(Size, Origin);

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

#if !SCUDO_FUCHSIA
   testIteratePrimary<scudo::SizeClassAllocator32<SizeClassMap, 18U>>();
 #endif
   testIteratePrimary<scudo::SizeClassAllocator64<SizeClassMap, 24U>>();
   testIteratePrimary<scudo::SizeClassAllocator64<SizeClassMap, 24U, true>>();
 }
 
 static std::mutex Mutex;
 static std::condition_variable Cv;
-static bool Ready = false;
+static bool Ready;
 
 template <typename Primary> static void performAllocations(Primary *Allocator) {
   static THREADLOCAL typename Primary::CacheT Cache;
   Cache.init(nullptr, Allocator);
   std::vector<std::pair<scudo::uptr, void *>> V;
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     while (!Ready)
while (!V.empty()) {
     auto Pair = V.back();
     Cache.deallocate(Pair.first, Pair.second);
     V.pop_back();
   }
   Cache.destroy(nullptr);
 }
 
 template <typename Primary> static void testPrimaryThreaded() {
+  Ready = false;
   auto Deleter = [](Primary *P) {
     P->unmapTestOnly();
     delete P;
   };
   std::unique_ptr<Primary, decltype(Deleter)> Allocator(new Primary, Deleter);
   Allocator->init(/*ReleaseToOsInterval=*/-1);
   std::thread Threads[32];
   for (scudo::uptr I = 0; I < ARRAY_SIZE(Threads); I++)

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();
 }
 
+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));
+  if (L->canCache(0U)) {
+    // 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));
+  }
+}
+
 static std::mutex Mutex;
 static std::condition_variable Cv;
-static bool Ready = false;
+static bool Ready;
 
 static void performAllocations(LargeAllocator *L) {
   std::vector<void *> V;
   const scudo::uptr PageSize = scudo::getPageSizeCached();
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     while (!Ready)
       Cv.wait(Lock);
static void performAllocations(LargeAllocator *L) {
   }
   while (!V.empty()) {
     L->deallocate(V.back());
     V.pop_back();
   }
 }
 
 TEST(ScudoSecondaryTest, SecondaryThreadsRace) {
-  LargeAllocator *L = new LargeAllocator;
+  Ready = false;
+  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/tests/tsd_test.cpp

 //===-- tsd_test.cpp --------------------------------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 
 #include "tests/scudo_unit_test.h"
 
 #include "tsd_exclusive.h"
 #include "tsd_shared.h"
 
 #include <condition_variable>
 #include <mutex>
+#include <set>
 #include <thread>
 
 // We mock out an allocator with a TSD registry, mostly using empty stubs. The
 // cache contains a single volatile uptr, to be able to test that several
 // concurrent threads will not access or modify the same cache at the same time.
 template <class Config> class MockAllocator {
 public:
   using ThisT = MockAllocator<Config>;

 
 private:
   bool Initialized;
   TSDRegistryT TSDRegistry;
 };
 
 struct OneCache {
   template <class Allocator>
-  using TSDRegistryT = scudo::TSDRegistrySharedT<Allocator, 1U>;
+  using TSDRegistryT = scudo::TSDRegistrySharedT<Allocator, 1U, 1U>;
 };
 
 struct SharedCaches {
   template <class Allocator>
-  using TSDRegistryT = scudo::TSDRegistrySharedT<Allocator, 16U>;
+  using TSDRegistryT = scudo::TSDRegistrySharedT<Allocator, 16U, 8U>;
 };
 
 struct ExclusiveCaches {
   template <class Allocator>
   using TSDRegistryT = scudo::TSDRegistryExT<Allocator>;
 };
 
 TEST(ScudoTSDTest, TSDRegistryInit) {
TEST(ScudoTSDTest, TSDRegistryBasic) {
   testRegistry<MockAllocator<SharedCaches>>();
 #if !SCUDO_FUCHSIA
   testRegistry<MockAllocator<ExclusiveCaches>>();
 #endif
 }
 
 static std::mutex Mutex;
 static std::condition_variable Cv;
-static bool Ready = false;
+static bool Ready;
 
 template <typename AllocatorT> static void stressCache(AllocatorT *Allocator) {
   auto Registry = Allocator->getTSDRegistry();
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     while (!Ready)
       Cv.wait(Lock);
   }
template <typename AllocatorT> static void stressCache(AllocatorT *Allocator) {
   // Loop a few times to make sure that a concurrent thread isn't modifying it.
   for (scudo::uptr I = 0; I < 4096U; I++)
     EXPECT_EQ(TSD->Cache.Canary, Canary);
   if (UnlockRequired)
     TSD->unlock();
 }
 
 template <class AllocatorT> static void testRegistryThreaded() {
+  Ready = false;
   auto Deleter = [](AllocatorT *A) {
     A->unmapTestOnly();
     delete A;
   };
   std::unique_ptr<AllocatorT, decltype(Deleter)> Allocator(new AllocatorT,
                                                            Deleter);
   Allocator->reset();
   std::thread Threads[32];

 
 TEST(ScudoTSDTest, TSDRegistryThreaded) {
   testRegistryThreaded<MockAllocator<OneCache>>();
   testRegistryThreaded<MockAllocator<SharedCaches>>();
 #if !SCUDO_FUCHSIA
   testRegistryThreaded<MockAllocator<ExclusiveCaches>>();
 #endif
 }
+
+static std::set<void *> Pointers;
+
+static void stressSharedRegistry(MockAllocator<SharedCaches> *Allocator) {
+  std::set<void *> Set;
+  auto Registry = Allocator->getTSDRegistry();
+  {
+    std::unique_lock<std::mutex> Lock(Mutex);
+    while (!Ready)
+      Cv.wait(Lock);
+  }
+  Registry->initThreadMaybe(Allocator, /*MinimalInit=*/false);
+  bool UnlockRequired;
+  for (scudo::uptr I = 0; I < 4096U; I++) {
+    auto TSD = Registry->getTSDAndLock(&UnlockRequired);
+    EXPECT_NE(TSD, nullptr);
+    Set.insert(reinterpret_cast<void *>(TSD));
+    if (UnlockRequired)
+      TSD->unlock();
+  }
+  {
+    std::unique_lock<std::mutex> Lock(Mutex);
+    Pointers.insert(Set.begin(), Set.end());
+  }
+}
+
+TEST(ScudoTSDTest, TSDRegistryTSDsCount) {
+  Ready = false;
+  using AllocatorT = MockAllocator<SharedCaches>;
+  auto Deleter = [](AllocatorT *A) {
+    A->unmapTestOnly();
+    delete A;
+  };
+  std::unique_ptr<AllocatorT, decltype(Deleter)> Allocator(new AllocatorT,
+                                                           Deleter);
+  Allocator->reset();
+  // We attempt to use as many TSDs as the shared cache offers by creating a
+  // decent amount of threads that will be run concurrently and attempt to get
+  // and lock TSDs. We put them all in a set and count the number of entries
+  // after we are done.
+  std::thread Threads[32];
+  for (scudo::uptr I = 0; I < ARRAY_SIZE(Threads); I++)
+    Threads[I] = std::thread(stressSharedRegistry, Allocator.get());
+  {
+    std::unique_lock<std::mutex> Lock(Mutex);
+    Ready = true;
+    Cv.notify_all();
+  }
+  for (auto &T : Threads)
+    T.join();
+  // The initial number of TSDs we get will be the minimum of the default count
+  // and the number of CPUs.
+  EXPECT_LE(Pointers.size(), 8U);
+  Pointers.clear();
+  auto Registry = Allocator->getTSDRegistry();
+  // Increase the number of TSDs to 16.
+  Registry->setOption(scudo::Option::MaxTSDsCount, 16);
+  Ready = false;
+  for (scudo::uptr I = 0; I < ARRAY_SIZE(Threads); I++)
+    Threads[I] = std::thread(stressSharedRegistry, Allocator.get());
+  {
+    std::unique_lock<std::mutex> Lock(Mutex);
+    Ready = true;
+    Cv.notify_all();
+  }
+  for (auto &T : Threads)
+    T.join();
+  // We should get 16 distinct TSDs back.
+  EXPECT_EQ(Pointers.size(), 16U);
+}

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

static void *enableMalloc(void *Unused) {
   sleep(1);
   malloc_enable();
 
   return nullptr;
 }
 
 TEST(ScudoWrappersCTest, DisableForkEnable) {
   pthread_t ThreadId;
+  Ready = false;
   EXPECT_EQ(pthread_create(&ThreadId, nullptr, &enableMalloc, nullptr), 0);
 
   // Wait for the thread to be warmed up.
   pthread_mutex_lock(&Mutex);
   while (!Ready)
     pthread_cond_wait(&Conditional, &Mutex);
   pthread_mutex_unlock(&Mutex);
 

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

TEST(ScudoWrappersCppTest, New) {
   testCxxNew<float>();
   testCxxNew<double>();
   testCxxNew<long double>();
   testCxxNew<Pixel>();
 }
 
 static std::mutex Mutex;
 static std::condition_variable Cv;
-static bool Ready = false;
+static bool Ready;
 
 static void stressNew() {
   std::vector<uintptr_t *> V;
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     while (!Ready)
       Cv.wait(Lock);
   }
   for (size_t I = 0; I < 256U; I++) {
     const size_t N = std::rand() % 128U;
     uintptr_t *P = new uintptr_t[N];
     if (P) {
       memset(P, 0x42, sizeof(uintptr_t) * N);
       V.push_back(P);
     }
   }
   while (!V.empty()) {
     delete[] V.back();
     V.pop_back();
   }
 }
 
 TEST(ScudoWrappersCppTest, ThreadedNew) {
+  Ready = false;
   std::thread Threads[32];
   for (size_t I = 0U; I < sizeof(Threads) / sizeof(Threads[0]); I++)
     Threads[I] = std::thread(stressNew);
   {
     std::unique_lock<std::mutex> Lock(Mutex);
     Ready = true;
     Cv.notify_all();
   }

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

template <class Allocator> struct TSDRegistryExT {
   }
 
   void enable() {
     atomic_store(&Disabled, 0U, memory_order_release);
     FallbackTSD.unlock();
     Mutex.unlock();
   }
 
+  bool setOption(Option O, UNUSED sptr Value) {
+    if (O == Option::MaxTSDsCount)
+      return false;
+    return true;
+  }
+
 private:
   void initOnceMaybe(Allocator *Instance) {
     ScopedLock L(Mutex);
     if (LIKELY(Initialized))
       return;
     initLinkerInitialized(Instance); // Sets Initialized.
   }
 

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

 //===-- tsd_shared.h --------------------------------------------*- 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_TSD_SHARED_H_
 #define SCUDO_TSD_SHARED_H_
 
 #include "linux.h" // for getAndroidTlsPtr()
 #include "tsd.h"
 
 namespace scudo {
 
-template <class Allocator, u32 MaxTSDCount> struct TSDRegistrySharedT {
+template <class Allocator, u32 TSDsArraySize, u32 DefaultTSDCount>
+struct TSDRegistrySharedT {
   void initLinkerInitialized(Allocator *Instance) {
     Instance->initLinkerInitialized();
     CHECK_EQ(pthread_key_create(&PThreadKey, nullptr), 0); // For non-TLS
-    const u32 NumberOfCPUs = getNumberOfCPUs();
-    NumberOfTSDs = (SCUDO_ANDROID || NumberOfCPUs == 0)
-                       ? MaxTSDCount
-                       : Min(NumberOfCPUs, MaxTSDCount);
-    for (u32 I = 0; I < NumberOfTSDs; I++)
+    for (u32 I = 0; I < TSDsArraySize; I++)
       TSDs[I].initLinkerInitialized(Instance);
-    // Compute all the coprimes of NumberOfTSDs. This will be used to walk the
-    // array of TSDs in a random order. For details, see:
-    // https://lemire.me/blog/2017/09/18/visiting-all-values-in-an-array-exactly-once-in-random-order/
-    for (u32 I = 0; I < NumberOfTSDs; I++) {
-      u32 A = I + 1;
-      u32 B = NumberOfTSDs;
-      // Find the GCD between I + 1 and NumberOfTSDs. If 1, they are coprimes.
-      while (B != 0) {
-        const u32 T = A;
-        A = B;
-        B = T % B;
-      }
-      if (A == 1)
-        CoPrimes[NumberOfCoPrimes++] = I + 1;
-    }
+    const u32 NumberOfCPUs = getNumberOfCPUs();
+    setNumberOfTSDs((NumberOfCPUs == 0) ? DefaultTSDCount
+                                        : Min(NumberOfCPUs, DefaultTSDCount));
     Initialized = true;
   }
   void init(Allocator *Instance) {
     memset(this, 0, sizeof(*this));
     initLinkerInitialized(Instance);
   }
 
   void unmapTestOnly() {
struct TSDRegistrySharedT {
   ALWAYS_INLINE TSD<Allocator> *getTSDAndLock(bool *UnlockRequired) {
     TSD<Allocator> *TSD = getCurrentTSD();
     DCHECK(TSD);
     *UnlockRequired = true;
     // Try to lock the currently associated context.
     if (TSD->tryLock())
       return TSD;
     // If that fails, go down the slow path.
+    if (TSDsArraySize == 1U) {
+      // Only 1 TSD, not need to go any further.
+      // The compiler will optimize this one way or the other.
+      TSD->lock();
+      return TSD;
+    }
     return getTSDAndLockSlow(TSD);
   }
 
   void disable() {
     Mutex.lock();
-    for (u32 I = 0; I < NumberOfTSDs; I++)
+    for (u32 I = 0; I < TSDsArraySize; I++)
       TSDs[I].lock();
   }
 
   void enable() {
-    for (s32 I = static_cast<s32>(NumberOfTSDs - 1); I >= 0; I--)
+    for (s32 I = static_cast<s32>(TSDsArraySize - 1); I >= 0; I--)
       TSDs[I].unlock();
     Mutex.unlock();
   }
 
+  bool setOption(Option O, sptr Value) {
+    if (O == Option::MaxTSDsCount)
+      return setNumberOfTSDs(static_cast<u32>(Value));
+    // Not supported by the TSD Registry, but not an error either.
+    return true;
+  }
+
 private:
   ALWAYS_INLINE void setCurrentTSD(TSD<Allocator> *CurrentTSD) {
 #if _BIONIC
     *getAndroidTlsPtr() = reinterpret_cast<uptr>(CurrentTSD);
 #elif SCUDO_LINUX
     ThreadTSD = CurrentTSD;
 #else
     CHECK_EQ(
         pthread_setspecific(PThreadKey, reinterpret_cast<void *>(CurrentTSD)),
         0);
 #endif
   }
 
   ALWAYS_INLINE TSD<Allocator> *getCurrentTSD() {
 #if _BIONIC
     return reinterpret_cast<TSD<Allocator> *>(*getAndroidTlsPtr());
 #elif SCUDO_LINUX
     return ThreadTSD;
 #else
     return reinterpret_cast<TSD<Allocator> *>(pthread_getspecific(PThreadKey));
 #endif
   }
 
+  bool setNumberOfTSDs(u32 N) {
+    ScopedLock L(MutexTSDs);
+    if (N < NumberOfTSDs)
+      return false;
+    if (N > TSDsArraySize)
+      N = TSDsArraySize;
+    NumberOfTSDs = N;
+    NumberOfCoPrimes = 0;
+    // Compute all the coprimes of NumberOfTSDs. This will be used to walk the
+    // array of TSDs in a random order. For details, see:
+    // https://lemire.me/blog/2017/09/18/visiting-all-values-in-an-array-exactly-once-in-random-order/
+    for (u32 I = 0; I < N; I++) {
+      u32 A = I + 1;
+      u32 B = N;
+      // Find the GCD between I + 1 and N. If 1, they are coprimes.
+      while (B != 0) {
+        const u32 T = A;
+        A = B;
+        B = T % B;
+      }
+      if (A == 1)
+        CoPrimes[NumberOfCoPrimes++] = I + 1;
+    }
+    return true;
+  }
+
   void initOnceMaybe(Allocator *Instance) {
     ScopedLock L(Mutex);
     if (LIKELY(Initialized))
       return;
     initLinkerInitialized(Instance); // Sets Initialized.
   }
 
   NOINLINE void initThread(Allocator *Instance) {
     initOnceMaybe(Instance);
     // Initial context assignment is done in a plain round-robin fashion.
     const u32 Index = atomic_fetch_add(&CurrentIndex, 1U, memory_order_relaxed);
     setCurrentTSD(&TSDs[Index % NumberOfTSDs]);
     Instance->callPostInitCallback();
   }
 
   NOINLINE TSD<Allocator> *getTSDAndLockSlow(TSD<Allocator> *CurrentTSD) {
-    if (MaxTSDCount > 1U && NumberOfTSDs > 1U) {
-      // Use the Precedence of the current TSD as our random seed. Since we are
-      // in the slow path, it means that tryLock failed, and as a result it's
-      // very likely that said Precedence is non-zero.
-      const u32 R = static_cast<u32>(CurrentTSD->getPrecedence());
-      const u32 Inc = CoPrimes[R % NumberOfCoPrimes];
-      u32 Index = R % NumberOfTSDs;
+    u32 N, Inc;
+    {
+      ScopedLock L(MutexTSDs);
+      N = NumberOfTSDs;
+      DCHECK_NE(NumberOfCoPrimes, 0U);
+      Inc = CoPrimes[R % NumberOfCoPrimes];
+    }
+    if (N > 1U) {
+      u32 Index = R % N;
       uptr LowestPrecedence = UINTPTR_MAX;
       TSD<Allocator> *CandidateTSD = nullptr;
       // Go randomly through at most 4 contexts and find a candidate.
-      for (u32 I = 0; I < Min(4U, NumberOfTSDs); I++) {
+      for (u32 I = 0; I < Min(4U, N); I++) {
         if (TSDs[Index].tryLock()) {
           setCurrentTSD(&TSDs[Index]);
           return &TSDs[Index];
         }
         const uptr Precedence = TSDs[Index].getPrecedence();
         // A 0 precedence here means another thread just locked this TSD.
         if (Precedence && Precedence < LowestPrecedence) {
           CandidateTSD = &TSDs[Index];
           LowestPrecedence = Precedence;
         }
         Index += Inc;
-        if (Index >= NumberOfTSDs)
-          Index -= NumberOfTSDs;
+        if (Index >= N)
+          Index -= N;
       }
       if (CandidateTSD) {
         CandidateTSD->lock();
         setCurrentTSD(CandidateTSD);
         return CandidateTSD;
       }
     }
     // Last resort, stick with the current one.
     CurrentTSD->lock();
     return CurrentTSD;
   }
 
   pthread_key_t PThreadKey;
   atomic_u32 CurrentIndex;
   u32 NumberOfTSDs;
   u32 NumberOfCoPrimes;
-  u32 CoPrimes[MaxTSDCount];
+  u32 CoPrimes[TSDsArraySize];
   bool Initialized;
   HybridMutex Mutex;
-  TSD<Allocator> TSDs[MaxTSDCount];
+  HybridMutex MutexTSDs;
+  TSD<Allocator> TSDs[TSDsArraySize];
 #if SCUDO_LINUX && !_BIONIC
   static THREADLOCAL TSD<Allocator> *ThreadTSD;
 #endif
 };
 
 #if SCUDO_LINUX && !_BIONIC
-template <class Allocator, u32 MaxTSDCount>
+template <class Allocator, u32 TSDsArraySize, u32 DefaultTSDCount>
 THREADLOCAL TSD<Allocator>
-    *TSDRegistrySharedT<Allocator, MaxTSDCount>::ThreadTSD;
+    *TSDRegistrySharedT<Allocator, TSDsArraySize, DefaultTSDCount>::ThreadTSD;
 #endif
 
 } // namespace scudo
 
 #endif // SCUDO_TSD_SHARED_H_