[scudo] Fix RingBuffer initialization.

[supersymetrie]

Summary

Several map implementations require that map calls provide a page
aligned size.

[fmayer]

LGTM, thanks.

Not in this CL: If we want to keep map requiring aligned sizes, I suggest we put a DCHECK into the linux one as well.

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

#endif // GWP_ASAN_HOOKS
   void initRingBuffer() {
     u32 AllocationRingBufferSize =
         static_cast<u32>(getFlags()->allocation_ring_buffer_size);
     // Have at least one entry so we don't need to special case.
     if (AllocationRingBufferSize < 1)
       AllocationRingBufferSize = 1;
     MapPlatformData Data = {};
     RawRingBuffer = static_cast<char *>(
-        map(/*Addr=*/nullptr, ringBufferSizeInBytes(AllocationRingBufferSize),
+        map(/*Addr=*/nullptr,
+            roundUpTo(ringBufferSizeInBytes(AllocationRingBufferSize), getPageSizeCached()),
             "AllocatorRingBuffer", /*Flags=*/0, &Data));
     auto *RingBuffer = reinterpret_cast<AllocationRingBuffer *>(RawRingBuffer);
     RingBuffer->Size = AllocationRingBufferSize;
     static_assert(sizeof(AllocationRingBuffer) %
                           alignof(typename AllocationRingBuffer::Entry) ==
                       0,
                   "invalid alignment");
   }