1 files changed, 142 insertions, 0 deletions
diff --git a/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h b/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h
new file mode 100644
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+++ b/toolkit/xre/dllservices/mozglue/interceptor/RangeMap.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_interceptor_RangeMap_h
+#define mozilla_interceptor_RangeMap_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/Span.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+
+#include <algorithm>
+
+namespace mozilla {
+namespace interceptor {
+
+/**
+ * This class maintains a vector of VMSharingPolicyUnique objects, sorted on
+ * the memory range that is used for reserving each object.
+ *
+ * This is used by VMSharingPolicyShared for creating and looking up VM regions
+ * that are within proximity of the applicable range.
+ *
+ * VMSharingPolicyUnique objects managed by this class are reused whenever
+ * possible. If no range is required, we just return the first available
+ * policy.
+ *
+ * If no range is required and no policies have yet been allocated, we create
+ * a new one with a null range as a default.
+ */
+template <typename MMPolicyT>
+class RangeMap final {
+ private:
+  /**
+   * This class is used as the comparison key for sorting and insertion.
+   */
+  class Range {
+   public:
+    constexpr Range() : mBase(0), mLimit(0) {}
+
+    explicit Range(const Maybe<Span<const uint8_t>>& aBounds)
+        : mBase(aBounds ? reinterpret_cast<const uintptr_t>(
+                              MMPolicyT::GetLowerBound(aBounds.ref()))
+                        : 0),
+          mLimit(aBounds ? reinterpret_cast<const uintptr_t>(
+                               MMPolicyT::GetUpperBoundIncl(aBounds.ref()))
+                         : 0) {}
+
+    Range& operator=(const Range&) = default;
+    Range(const Range&) = default;
+    Range(Range&&) = default;
+    Range& operator=(Range&&) = default;
+
+    bool operator<(const Range& aOther) const {
+      return mBase < aOther.mBase ||
+             (mBase == aOther.mBase && mLimit < aOther.mLimit);
+    }
+
+    bool Contains(const Range& aOther) const {
+      return mBase <= aOther.mBase && mLimit >= aOther.mLimit;
+    }
+
+   private:
+    uintptr_t mBase;
+    uintptr_t mLimit;
+  };
+
+  class PolicyInfo final : public Range {
+   public:
+    explicit PolicyInfo(const Range& aRange)
+        : Range(aRange),
+          mPolicy(MakeUnique<VMSharingPolicyUnique<MMPolicyT>>()) {}
+
+    PolicyInfo(const PolicyInfo&) = delete;
+    PolicyInfo& operator=(const PolicyInfo&) = delete;
+
+    PolicyInfo(PolicyInfo&& aOther) = default;
+    PolicyInfo& operator=(PolicyInfo&& aOther) = default;
+
+    VMSharingPolicyUnique<MMPolicyT>* GetPolicy() { return mPolicy.get(); }
+
+   private:
+    UniquePtr<VMSharingPolicyUnique<MMPolicyT>> mPolicy;
+  };
+
+  using VectorType = Vector<PolicyInfo, 0, InfallibleAllocPolicy>;
+
+ public:
+  constexpr RangeMap() : mPolicies(nullptr) {}
+
+  VMSharingPolicyUnique<MMPolicyT>* GetPolicy(
+      const Maybe<Span<const uint8_t>>& aBounds) {
+    Range testRange(aBounds);
+
+    if (!mPolicies) {
+      mPolicies = new VectorType();
+    }
+
+    // If no bounds are specified, we just use the first available policy
+    if (!aBounds) {
+      if (mPolicies->empty()) {
+        if (!mPolicies->append(PolicyInfo(testRange))) {
+          return nullptr;
+        }
+      }
+
+      return GetFirstPolicy();
+    }
+
+    // mPolicies is sorted, so we search
+    auto itr =
+        std::lower_bound(mPolicies->begin(), mPolicies->end(), testRange);
+    if (itr != mPolicies->end() && itr->Contains(testRange)) {
+      return itr->GetPolicy();
+    }
+
+    itr = mPolicies->insert(itr, PolicyInfo(testRange));
+
+    MOZ_ASSERT(std::is_sorted(mPolicies->begin(), mPolicies->end()));
+
+    return itr->GetPolicy();
+  }
+
+ private:
+  VMSharingPolicyUnique<MMPolicyT>* GetFirstPolicy() {
+    MOZ_RELEASE_ASSERT(mPolicies && !mPolicies->empty());
+    return mPolicies->begin()->GetPolicy();
+  }
+
+ private:
+  VectorType* mPolicies;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_RangeMap_h