[scudo][standalone] Fuchsia related fixes

[cryptoad]

Summary

While attempting to roll the latest Scudo in Fuchsia, some issues
arose. While trying to debug them, it appeared that DCHECKs were
also never exercised in Fuchsia. This CL fixes the following
problems:

• the size of a block in the TransferBatch class must be a multiple of the compact pointer scale. In some cases, it wasn't true, which lead to obscure crashes. Now, we round up sizeof(TransferBatch). This only materialized in Fuchsia due to the specific parameters of the DefaultConfig;
• 2 DCHECK statements in Fuchsia were incorrect;
• map() & co. require a size multiple of a page (as enforced in Fuchsia DCHECKs), which wasn't the case for PackedCounters.
• In the Secondary, a parameter was marked as UNUSED while it is actually used.

[vitalybuka]

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

83–96

maybe

[cryptoad]

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

83–96

getBufferSize() is used in the tests and has to correlate to the size of the packed counters array, not the actual mapping size which can be larger.
If changing BufferSize here, the tests fail.

compiler-rt/lib/scudo/standalone/fuchsia.cpp

if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
       dieOnMapUnmapError(Status == ZX_ERR_NO_MEMORY);
     return nullptr;
   }
   return reinterpret_cast<void *>(Data->VmarBase);
 }
 
 void *map(void *Addr, uptr Size, const char *Name, uptr Flags,
           MapPlatformData *Data) {
-  DCHECK_EQ(Size % PAGE_SIZE, 0);
+  DCHECK_EQ(Size % getPageSizeCached(), 0);
   const bool AllowNoMem = !!(Flags & MAP_ALLOWNOMEM);
 
   // For MAP_NOACCESS, just allocate a Vmar and return.
   if (Flags & MAP_NOACCESS)
     return allocateVmar(Size, Data, AllowNoMem);
 
   const zx_handle_t Vmar = Data ? Data->Vmar : _zx_vmar_root_self();
   CHECK_NE(Vmar, ZX_HANDLE_INVALID);
void *map(void *Addr, uptr Size, const char *Name, uptr Flags,
   const uint64_t Offset =
       Addr ? reinterpret_cast<uintptr_t>(Addr) - Data->VmarBase : 0;
   if (Offset)
     MapFlags |= ZX_VM_SPECIFIC;
   Status = _zx_vmar_map(Vmar, MapFlags, Offset, Vmo, VmoSize, Size, &P);
   // No need to track the Vmo if we don't intend on resizing it. Close it.
   if (Flags & MAP_RESIZABLE) {
     DCHECK(Data);
-    DCHECK_EQ(Data->Vmo, ZX_HANDLE_INVALID);
+    if (Data->Vmo == ZX_HANDLE_INVALID)
       Data->Vmo = Vmo;
+    else
+      DCHECK_EQ(Data->Vmo, Vmo);
   } else {
     CHECK_EQ(_zx_handle_close(Vmo), ZX_OK);
   }
   if (UNLIKELY(Status != ZX_OK)) {
     if (Status != ZX_ERR_NO_MEMORY || !AllowNoMem)
       dieOnMapUnmapError(Status == ZX_ERR_NO_MEMORY);
     return nullptr;
   }

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

public:
   static const uptr CompactPtrScale = Config::PrimaryCompactPtrScale;
   typedef typename Config::SizeClassMap SizeClassMap;
   typedef SizeClassAllocator64<Config> ThisT;
   typedef SizeClassAllocatorLocalCache<ThisT> CacheT;
   typedef typename CacheT::TransferBatch TransferBatch;
 
   static uptr getSizeByClassId(uptr ClassId) {
     return (ClassId == SizeClassMap::BatchClassId)
-               ? sizeof(TransferBatch)
+               ? roundUpTo(sizeof(TransferBatch), 1U << CompactPtrScale)
                : SizeClassMap::getSizeByClassId(ClassId);
   }
 
   static bool canAllocate(uptr Size) { return Size <= SizeClassMap::MaxSize; }
 
   void initLinkerInitialized(s32 ReleaseToOsInterval) {
     // Reserve the space required for the Primary.
     PrimaryBase = reinterpret_cast<uptr>(

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

SizePerRegion =
         roundUpTo(NumCounters, static_cast<uptr>(1U) << PackingRatioLog) >>
         PackingRatioLog;
     BufferSize = SizePerRegion * sizeof(*Buffer) * Regions;
     if (BufferSize <= (StaticBufferCount * sizeof(Buffer[0])) &&
         Mutex.tryLock()) {
       Buffer = &StaticBuffer[0];
       memset(Buffer, 0, BufferSize);
     } else {
       Buffer = reinterpret_cast<uptr *>(
-          map(nullptr, BufferSize, "scudo:counters", MAP_ALLOWNOMEM));
+          map(nullptr, roundUpTo(BufferSize, getPageSizeCached()),
+              "scudo:counters", MAP_ALLOWNOMEM));
     }
   }
   ~PackedCounterArray() {
     if (!isAllocated())
       return;
     if (Buffer == &StaticBuffer[0])
       Mutex.unlock();
     else
-      unmap(reinterpret_cast<void *>(Buffer), BufferSize);
+      unmap(reinterpret_cast<void *>(Buffer),
+            roundUpTo(BufferSize, getPageSizeCached()));
   }
 
   bool isAllocated() const { return !!Buffer; }
 
   uptr getCount() const { return NumCounters; }
 
   uptr get(uptr Region, uptr I) const {
     DCHECK_LT(Region, Regions);
     DCHECK_LT(I, NumCounters);

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

 class MapAllocatorNoCache {
 public:
   void initLinkerInitialized(UNUSED s32 ReleaseToOsInterval) {}
   void init(UNUSED s32 ReleaseToOsInterval) {}
   bool retrieve(UNUSED Options Options, UNUSED uptr Size, UNUSED uptr Alignment,
                 UNUSED LargeBlock::Header **H, UNUSED bool *Zeroed) {
     return false;
   }
-  void store(UNUSED Options Options, UNUSED LargeBlock::Header *H) { unmap(H); }
+  void store(UNUSED Options Options, LargeBlock::Header *H) { unmap(H); }
   bool canCache(UNUSED uptr Size) { return false; }
   void disable() {}
   void enable() {}
   void releaseToOS() {}
   void disableMemoryTagging() {}
   bool setOption(Option O, UNUSED sptr Value) {
     if (O == Option::ReleaseInterval || O == Option::MaxCacheEntriesCount ||
         O == Option::MaxCacheEntrySize)