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diff --git a/contrib/llvm-project/compiler-rt/lib/hwasan/hwasan_thread_list.h b/contrib/llvm-project/compiler-rt/lib/hwasan/hwasan_thread_list.h
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+//===-- hwasan_thread_list.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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of HWAddressSanitizer.
+//
+//===----------------------------------------------------------------------===//
+
+// HwasanThreadList is a registry for live threads, as well as an allocator for
+// HwasanThread objects and their stack history ring buffers. There are
+// constraints on memory layout of the shadow region and CompactRingBuffer that
+// are part of the ABI contract between compiler-rt and llvm.
+//
+// * Start of the shadow memory region is aligned to 2**kShadowBaseAlignment.
+// * All stack ring buffers are located within (2**kShadowBaseAlignment)
+// sized region below and adjacent to the shadow region.
+// * Each ring buffer has a size of (2**N)*4096 where N is in [0, 8), and is
+// aligned to twice its size. The value of N can be different for each buffer.
+//
+// These constrains guarantee that, given an address A of any element of the
+// ring buffer,
+//     A_next = (A + sizeof(uptr)) & ~((1 << (N + 13)) - 1)
+//   is the address of the next element of that ring buffer (with wrap-around).
+// And, with K = kShadowBaseAlignment,
+//     S = (A | ((1 << K) - 1)) + 1
+//   (align up to kShadowBaseAlignment) is the start of the shadow region.
+//
+// These calculations are used in compiler instrumentation to update the ring
+// buffer and obtain the base address of shadow using only two inputs: address
+// of the current element of the ring buffer, and N (i.e. size of the ring
+// buffer). Since the value of N is very limited, we pack both inputs into a
+// single thread-local word as
+//   (1 << (N + 56)) | A
+// See the implementation of class CompactRingBuffer, which is what is stored in
+// said thread-local word.
+//
+// Note the unusual way of aligning up the address of the shadow:
+//   (A | ((1 << K) - 1)) + 1
+// It is only correct if A is not already equal to the shadow base address, but
+// it saves 2 instructions on AArch64.
+
+#include "hwasan.h"
+#include "hwasan_allocator.h"
+#include "hwasan_flags.h"
+#include "hwasan_thread.h"
+
+#include "sanitizer_common/sanitizer_placement_new.h"
+
+namespace __hwasan {
+
+static uptr RingBufferSize() {
+  uptr desired_bytes = flags()->stack_history_size * sizeof(uptr);
+  // FIXME: increase the limit to 8 once this bug is fixed:
+  // https://bugs.llvm.org/show_bug.cgi?id=39030
+  for (int shift = 1; shift < 7; ++shift) {
+    uptr size = 4096 * (1ULL << shift);
+    if (size >= desired_bytes)
+      return size;
+  }
+  Printf("stack history size too large: %d\n", flags()->stack_history_size);
+  CHECK(0);
+  return 0;
+}
+
+struct ThreadStats {
+  uptr n_live_threads;
+  uptr total_stack_size;
+};
+
+class HwasanThreadList {
+ public:
+  HwasanThreadList(uptr storage, uptr size)
+      : free_space_(storage), free_space_end_(storage + size) {
+    // [storage, storage + size) is used as a vector of
+    // thread_alloc_size_-sized, ring_buffer_size_*2-aligned elements.
+    // Each element contains
+    // * a ring buffer at offset 0,
+    // * a Thread object at offset ring_buffer_size_.
+    ring_buffer_size_ = RingBufferSize();
+    thread_alloc_size_ =
+        RoundUpTo(ring_buffer_size_ + sizeof(Thread), ring_buffer_size_ * 2);
+  }
+
+  Thread *CreateCurrentThread() {
+    Thread *t;
+    {
+      SpinMutexLock l(&list_mutex_);
+      if (!free_list_.empty()) {
+        t = free_list_.back();
+        free_list_.pop_back();
+        uptr start = (uptr)t - ring_buffer_size_;
+        internal_memset((void *)start, 0, ring_buffer_size_ + sizeof(Thread));
+      } else {
+        t = AllocThread();
+      }
+      live_list_.push_back(t);
+    }
+    t->Init((uptr)t - ring_buffer_size_, ring_buffer_size_);
+    AddThreadStats(t);
+    return t;
+  }
+
+  void DontNeedThread(Thread *t) {
+    uptr start = (uptr)t - ring_buffer_size_;
+    ReleaseMemoryPagesToOS(start, start + thread_alloc_size_);
+  }
+
+  void RemoveThreadFromLiveList(Thread *t) {
+    for (Thread *&t2 : live_list_)
+      if (t2 == t) {
+        // To remove t2, copy the last element of the list in t2's position, and
+        // pop_back(). This works even if t2 is itself the last element.
+        t2 = live_list_.back();
+        live_list_.pop_back();
+        return;
+      }
+    CHECK(0 && "thread not found in live list");
+  }
+
+  void ReleaseThread(Thread *t) {
+    RemoveThreadStats(t);
+    t->Destroy();
+    SpinMutexLock l(&list_mutex_);
+    RemoveThreadFromLiveList(t);
+    free_list_.push_back(t);
+    DontNeedThread(t);
+  }
+
+  Thread *GetThreadByBufferAddress(uptr p) {
+    return (Thread *)(RoundDownTo(p, ring_buffer_size_ * 2) +
+                      ring_buffer_size_);
+  }
+
+  uptr MemoryUsedPerThread() {
+    uptr res = sizeof(Thread) + ring_buffer_size_;
+    if (auto sz = flags()->heap_history_size)
+      res += HeapAllocationsRingBuffer::SizeInBytes(sz);
+    return res;
+  }
+
+  template <class CB>
+  void VisitAllLiveThreads(CB cb) {
+    SpinMutexLock l(&list_mutex_);
+    for (Thread *t : live_list_) cb(t);
+  }
+
+  void AddThreadStats(Thread *t) {
+    SpinMutexLock l(&stats_mutex_);
+    stats_.n_live_threads++;
+    stats_.total_stack_size += t->stack_size();
+  }
+
+  void RemoveThreadStats(Thread *t) {
+    SpinMutexLock l(&stats_mutex_);
+    stats_.n_live_threads--;
+    stats_.total_stack_size -= t->stack_size();
+  }
+
+  ThreadStats GetThreadStats() {
+    SpinMutexLock l(&stats_mutex_);
+    return stats_;
+  }
+
+ private:
+  Thread *AllocThread() {
+    uptr align = ring_buffer_size_ * 2;
+    CHECK(IsAligned(free_space_, align));
+    Thread *t = (Thread *)(free_space_ + ring_buffer_size_);
+    free_space_ += thread_alloc_size_;
+    CHECK(free_space_ <= free_space_end_ && "out of thread memory");
+    return t;
+  }
+
+  uptr free_space_;
+  uptr free_space_end_;
+  uptr ring_buffer_size_;
+  uptr thread_alloc_size_;
+
+  InternalMmapVector<Thread *> free_list_;
+  InternalMmapVector<Thread *> live_list_;
+  SpinMutex list_mutex_;
+
+  ThreadStats stats_;
+  SpinMutex stats_mutex_;
+};
+
+void InitThreadList(uptr storage, uptr size);
+HwasanThreadList &hwasanThreadList();
+
+} // namespace