1 files changed, 517 insertions, 0 deletions
diff --git a/mozglue/misc/interceptor/Trampoline.h b/mozglue/misc/interceptor/Trampoline.h
new file mode 100644
index 0000000000..c471408bd1
--- /dev/null
+++ b/mozglue/misc/interceptor/Trampoline.h
@@ -0,0 +1,517 @@
+/* -*- 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_Trampoline_h
+#define mozilla_interceptor_Trampoline_h
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Types.h"
+#include "mozilla/WindowsProcessMitigations.h"
+
+namespace mozilla {
+namespace interceptor {
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS Trampoline final {
+ public:
+  Trampoline(const MMPolicy* aMMPolicy, uint8_t* const aLocalBase,
+             const uintptr_t aRemoteBase, const uint32_t aChunkSize)
+      : mMMPolicy(aMMPolicy),
+        mPrevLocalProt(0),
+        mLocalBase(aLocalBase),
+        mRemoteBase(aRemoteBase),
+        mOffset(0),
+        mExeOffset(0),
+        mMaxOffset(aChunkSize),
+        mAccumulatedStatus(true) {
+    if (!::VirtualProtect(aLocalBase, aChunkSize,
+                          MMPolicy::GetTrampWriteProtFlags(),
+                          &mPrevLocalProt)) {
+      mPrevLocalProt = 0;
+    }
+  }
+
+  Trampoline(Trampoline&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mPrevLocalProt(aOther.mPrevLocalProt),
+        mLocalBase(aOther.mLocalBase),
+        mRemoteBase(aOther.mRemoteBase),
+        mOffset(aOther.mOffset),
+        mExeOffset(aOther.mExeOffset),
+        mMaxOffset(aOther.mMaxOffset),
+        mAccumulatedStatus(aOther.mAccumulatedStatus) {
+    aOther.mPrevLocalProt = 0;
+    aOther.mAccumulatedStatus = false;
+  }
+
+  MOZ_IMPLICIT Trampoline(decltype(nullptr))
+      : mMMPolicy(nullptr),
+        mPrevLocalProt(0),
+        mLocalBase(nullptr),
+        mRemoteBase(0),
+        mOffset(0),
+        mExeOffset(0),
+        mMaxOffset(0),
+        mAccumulatedStatus(false) {}
+
+  Trampoline(const Trampoline&) = delete;
+  Trampoline& operator=(const Trampoline&) = delete;
+
+  Trampoline& operator=(Trampoline&& aOther) {
+    Clear();
+
+    mMMPolicy = aOther.mMMPolicy;
+    mPrevLocalProt = aOther.mPrevLocalProt;
+    mLocalBase = aOther.mLocalBase;
+    mRemoteBase = aOther.mRemoteBase;
+    mOffset = aOther.mOffset;
+    mExeOffset = aOther.mExeOffset;
+    mMaxOffset = aOther.mMaxOffset;
+    mAccumulatedStatus = aOther.mAccumulatedStatus;
+
+    aOther.mPrevLocalProt = 0;
+    aOther.mAccumulatedStatus = false;
+
+    return *this;
+  }
+
+  ~Trampoline() { Clear(); }
+
+  explicit operator bool() const {
+    return IsNull() ||
+           (mLocalBase && mRemoteBase && mPrevLocalProt && mAccumulatedStatus);
+  }
+
+  bool IsNull() const { return !mMMPolicy; }
+
+#if defined(_M_ARM64)
+
+  void WriteInstruction(uint32_t aInstruction) {
+    const uint32_t kDelta = sizeof(uint32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<uint32_t*>(mLocalBase + mOffset) = aInstruction;
+    mOffset += kDelta;
+  }
+
+  void WriteLoadLiteral(const uintptr_t aAddress, const uint8_t aReg) {
+    const uint32_t kDelta = sizeof(uint32_t) + sizeof(uintptr_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    // We grow the literal pool from the *end* of the tramp,
+    // so we need to ensure that there is enough room for both an instruction
+    // and a pointer
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mMaxOffset -= sizeof(uintptr_t);
+    *reinterpret_cast<uintptr_t*>(mLocalBase + mMaxOffset) = aAddress;
+
+    CheckedInt<intptr_t> pc(GetCurrentRemoteAddress());
+    if (!pc.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    CheckedInt<intptr_t> literal(reinterpret_cast<uintptr_t>(mLocalBase) +
+                                 mMaxOffset);
+    if (!literal.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    CheckedInt<intptr_t> ptrOffset = (literal - pc);
+    if (!ptrOffset.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // ptrOffset must be properly aligned
+    MOZ_ASSERT((ptrOffset.value() % 4) == 0);
+    ptrOffset /= 4;
+
+    CheckedInt<int32_t> offset(ptrOffset.value());
+    if (!offset.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // Ensure that offset falls within the range of a signed 19-bit value
+    if (offset.value() < -0x40000 || offset.value() > 0x3FFFF) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    const int32_t kimm19Mask = 0x7FFFF;
+    int32_t masked = offset.value() & kimm19Mask;
+
+    MOZ_ASSERT(aReg < 32);
+    uint32_t loadInstr = 0x58000000 | (masked << 5) | aReg;
+    WriteInstruction(loadInstr);
+  }
+
+#else
+
+  void WriteByte(uint8_t aValue) {
+    const uint32_t kDelta = sizeof(uint8_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset >= mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *(mLocalBase + mOffset) = aValue;
+    ++mOffset;
+  }
+
+  void WriteInteger(int32_t aValue) {
+    const uint32_t kDelta = sizeof(int32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<int32_t*>(mLocalBase + mOffset) = aValue;
+    mOffset += kDelta;
+  }
+
+  void WriteDisp32(uintptr_t aAbsTarget) {
+    const uint32_t kDelta = sizeof(int32_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    // This needs to be computed from the remote location
+    intptr_t remoteTrampPosition = static_cast<intptr_t>(mRemoteBase + mOffset);
+
+    intptr_t diff =
+        static_cast<intptr_t>(aAbsTarget) - (remoteTrampPosition + kDelta);
+
+    CheckedInt<int32_t> checkedDisp(diff);
+    MOZ_ASSERT(checkedDisp.isValid());
+    if (!checkedDisp.isValid()) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    int32_t disp = checkedDisp.value();
+    *reinterpret_cast<int32_t*>(mLocalBase + mOffset) = disp;
+    mOffset += kDelta;
+  }
+
+#endif
+
+  void WritePointer(uintptr_t aValue) {
+    const uint32_t kDelta = sizeof(uintptr_t);
+
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += kDelta;
+      return;
+    }
+
+    if (mOffset + kDelta > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    *reinterpret_cast<uintptr_t*>(mLocalBase + mOffset) = aValue;
+    mOffset += kDelta;
+  }
+
+  void WriteEncodedPointer(void* aValue) {
+    uintptr_t encoded = ReadOnlyTargetFunction<MMPolicy>::EncodePtr(aValue);
+    WritePointer(encoded);
+  }
+
+  Maybe<uintptr_t> ReadPointer() {
+    if (mOffset + sizeof(uintptr_t) > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return Nothing();
+    }
+
+    auto result = Some(*reinterpret_cast<uintptr_t*>(mLocalBase + mOffset));
+    mOffset += sizeof(uintptr_t);
+    return std::move(result);
+  }
+
+  Maybe<uintptr_t> ReadEncodedPointer() {
+    Maybe<uintptr_t> encoded(ReadPointer());
+    if (!encoded) {
+      return encoded;
+    }
+
+    return Some(ReadOnlyTargetFunction<MMPolicy>::DecodePtr(encoded.value()));
+  }
+
+#if defined(_M_IX86)
+  // 32-bit only
+  void AdjustDisp32AtOffset(uint32_t aOffset, uintptr_t aAbsTarget) {
+    uint32_t effectiveOffset = mExeOffset + aOffset;
+
+    if (effectiveOffset + sizeof(int32_t) > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    intptr_t diff = static_cast<intptr_t>(aAbsTarget) -
+                    static_cast<intptr_t>(mRemoteBase + mExeOffset);
+    *reinterpret_cast<int32_t*>(mLocalBase + effectiveOffset) += diff;
+  }
+#endif  // defined(_M_IX86)
+
+  void CopyFrom(uintptr_t aOrigBytes, uint32_t aNumBytes) {
+    if (!mMMPolicy) {
+      // Null tramp, just track offset
+      mOffset += aNumBytes;
+      return;
+    }
+
+    if (!mMMPolicy || mOffset + aNumBytes > mMaxOffset) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    if (!mMMPolicy->Read(mLocalBase + mOffset,
+                         reinterpret_cast<void*>(aOrigBytes), aNumBytes)) {
+      mAccumulatedStatus = false;
+      return;
+    }
+
+    mOffset += aNumBytes;
+  }
+
+  void Rewind() { mOffset = 0; }
+
+  uintptr_t GetCurrentRemoteAddress() const { return mRemoteBase + mOffset; }
+
+  void StartExecutableCode() {
+    MOZ_ASSERT(!mExeOffset);
+    mExeOffset = mOffset;
+  }
+
+  void* EndExecutableCode() const {
+    if (!mAccumulatedStatus || !mMMPolicy) {
+      return nullptr;
+    }
+
+    // This must always return the start address the executable code
+    // *in the target process*
+    return reinterpret_cast<void*>(mRemoteBase + mExeOffset);
+  }
+
+  uint32_t GetCurrentExecutableCodeLen() const { return mOffset - mExeOffset; }
+
+  Trampoline<MMPolicy>& operator--() {
+    MOZ_ASSERT(mOffset);
+    --mOffset;
+    return *this;
+  }
+
+ private:
+  void Clear() {
+    if (!mLocalBase || !mPrevLocalProt) {
+      return;
+    }
+
+    DebugOnly<bool> ok = !!::VirtualProtect(mLocalBase, mMaxOffset,
+                                            mPrevLocalProt, &mPrevLocalProt);
+    MOZ_ASSERT(ok);
+
+    mLocalBase = nullptr;
+    mRemoteBase = 0;
+    mPrevLocalProt = 0;
+    mAccumulatedStatus = false;
+  }
+
+ private:
+  const MMPolicy* mMMPolicy;
+  DWORD mPrevLocalProt;
+  uint8_t* mLocalBase;
+  uintptr_t mRemoteBase;
+  uint32_t mOffset;
+  uint32_t mExeOffset;
+  uint32_t mMaxOffset;
+  bool mAccumulatedStatus;
+};
+
+template <typename MMPolicy>
+class MOZ_STACK_CLASS TrampolineCollection final {
+ public:
+  class MOZ_STACK_CLASS TrampolineIterator final {
+   public:
+    Trampoline<MMPolicy> operator*() {
+      uint32_t offset = mCurTramp * mCollection.mTrampSize;
+      return Trampoline<MMPolicy>(nullptr, mCollection.mLocalBase + offset,
+                                  mCollection.mRemoteBase + offset,
+                                  mCollection.mTrampSize);
+    }
+
+    TrampolineIterator& operator++() {
+      ++mCurTramp;
+      return *this;
+    }
+
+    bool operator!=(const TrampolineIterator& aOther) const {
+      return mCurTramp != aOther.mCurTramp;
+    }
+
+   private:
+    explicit TrampolineIterator(
+        const TrampolineCollection<MMPolicy>& aCollection,
+        const uint32_t aCurTramp = 0)
+        : mCollection(aCollection), mCurTramp(aCurTramp) {}
+
+    const TrampolineCollection<MMPolicy>& mCollection;
+    uint32_t mCurTramp;
+
+    friend class TrampolineCollection<MMPolicy>;
+  };
+
+  explicit TrampolineCollection(const MMPolicy& aMMPolicy)
+      : mMMPolicy(aMMPolicy),
+        mLocalBase(0),
+        mRemoteBase(0),
+        mTrampSize(0),
+        mNumTramps(0),
+        mPrevProt(0),
+        mCS(nullptr) {}
+
+  TrampolineCollection(const MMPolicy& aMMPolicy, uint8_t* const aLocalBase,
+                       const uintptr_t aRemoteBase, const uint32_t aTrampSize,
+                       const uint32_t aNumTramps)
+      : mMMPolicy(aMMPolicy),
+        mLocalBase(aLocalBase),
+        mRemoteBase(aRemoteBase),
+        mTrampSize(aTrampSize),
+        mNumTramps(aNumTramps),
+        mPrevProt(0),
+        mCS(nullptr) {
+    if (!aNumTramps) {
+      return;
+    }
+
+    BOOL ok = mMMPolicy.Protect(aLocalBase, aNumTramps * aTrampSize,
+                                PAGE_EXECUTE_READWRITE, &mPrevProt);
+    if (!ok) {
+      // When destroying a sandboxed process that uses
+      // MITIGATION_DYNAMIC_CODE_DISABLE, we won't be allowed to write to our
+      // executable memory so we just do nothing.  If we fail to get access
+      // to memory for any other reason, we still don't want to crash but we
+      // do assert.
+      MOZ_ASSERT(IsDynamicCodeDisabled());
+      mNumTramps = 0;
+      mPrevProt = 0;
+    }
+  }
+
+  ~TrampolineCollection() {
+    if (!mPrevProt) {
+      return;
+    }
+
+    mMMPolicy.Protect(mLocalBase, mNumTramps * mTrampSize, mPrevProt,
+                      &mPrevProt);
+
+    if (mCS) {
+      ::LeaveCriticalSection(mCS);
+    }
+  }
+
+  void Lock(CRITICAL_SECTION& aCS) {
+    if (!mPrevProt || mCS) {
+      return;
+    }
+
+    mCS = &aCS;
+    ::EnterCriticalSection(&aCS);
+  }
+
+  TrampolineIterator begin() const {
+    if (!mPrevProt) {
+      return end();
+    }
+
+    return TrampolineIterator(*this);
+  }
+
+  TrampolineIterator end() const {
+    return TrampolineIterator(*this, mNumTramps);
+  }
+
+  TrampolineCollection(const TrampolineCollection&) = delete;
+  TrampolineCollection& operator=(const TrampolineCollection&) = delete;
+  TrampolineCollection& operator=(TrampolineCollection&&) = delete;
+
+  TrampolineCollection(TrampolineCollection&& aOther)
+      : mMMPolicy(aOther.mMMPolicy),
+        mLocalBase(aOther.mLocalBase),
+        mRemoteBase(aOther.mRemoteBase),
+        mTrampSize(aOther.mTrampSize),
+        mNumTramps(aOther.mNumTramps),
+        mPrevProt(aOther.mPrevProt),
+        mCS(aOther.mCS) {
+    aOther.mPrevProt = 0;
+    aOther.mCS = nullptr;
+  }
+
+ private:
+  const MMPolicy& mMMPolicy;
+  uint8_t* const mLocalBase;
+  const uintptr_t mRemoteBase;
+  const uint32_t mTrampSize;
+  uint32_t mNumTramps;
+  uint32_t mPrevProt;
+  CRITICAL_SECTION* mCS;
+
+  friend class TrampolineIterator;
+};
+
+}  // namespace interceptor
+}  // namespace mozilla
+
+#endif  // mozilla_interceptor_Trampoline_h