[compiler-rt] [scudo] [MTE] resize stack depot for allocation ring buffer (PR #74515)

[via llvm-commits]

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@@ -1504,6 +1529,28 @@ class Allocator {
       return;
     u32 AllocationRingBufferSize =
         static_cast<u32>(getFlags()->allocation_ring_buffer_size);
+    // We store alloc and free stacks for each entry.
+    constexpr auto kStacksPerRingBufferEntry = 2;
+    u32 TabSize = static_cast<u32>(roundUpPowerOfTwo(kStacksPerRingBufferEntry *
+                                                     AllocationRingBufferSize));
+    constexpr auto kFramesPerStack = 8;
+    static_assert(isPowerOfTwo(kFramesPerStack));
+    u32 RingSize = static_cast<u32>(TabSize * kFramesPerStack);
+    DCHECK(isPowerOfTwo(RingSize));
+    static_assert(sizeof(StackDepot) % alignof(atomic_u64) == 0);
+
+    StackDepotSize = sizeof(StackDepot) + sizeof(atomic_u64) * RingSize +
+                     sizeof(atomic_u32) * TabSize;
+    MemMapT DepotMap;
+    DepotMap.map(
+        /*Addr=*/0U, roundUp(StackDepotSize, getPageSizeCached()),
+        "scudo:stack_depot");
+    RawStackDepot = reinterpret_cast<char *>(DepotMap.getBase());
+    auto *Depot = reinterpret_cast<StackDepot *>(DepotMap.getBase());
+    Depot->init(RingSize, TabSize);
+    DCHECK(Depot->isValid(StackDepotSize));
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ChiaHungDuan wrote:

This DCHECK seems a little weird to me. We are creating the depot regarding the `StackDepotSize` but we verify the value *after* the creation.

Even if you want to check either `RingSize` or `TabSize`, I may suggest checking them in init()

https://github.com/llvm/llvm-project/pull/74515