Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 226 insertions, 0 deletions

diff --git a/js/src/wasm/WasmMemory.h b/js/src/wasm/WasmMemory.h
new file mode 100644
index 0000000000..ea2c61aa38
--- /dev/null
+++ b/js/src/wasm/WasmMemory.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:
+ *
+ * Copyright 2021 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef wasm_memory_h
+#define wasm_memory_h
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/Maybe.h"
+
+#include <stdint.h>
+
+#include "js/Value.h"
+#include "vm/NativeObject.h"
+#include "wasm/WasmConstants.h"
+#include "wasm/WasmValType.h"
+
+namespace js {
+namespace wasm {
+
+// Limits are parameterized by an IndexType which is used to index the
+// underlying resource (either a Memory or a Table). Tables are restricted to
+// I32, while memories may use I64 when memory64 is enabled.
+
+enum class IndexType : uint8_t { I32, I64 };
+
+inline ValType ToValType(IndexType it) {
+  return it == IndexType::I64 ? ValType::I64 : ValType::I32;
+}
+
+extern bool ToIndexType(JSContext* cx, HandleValue value, IndexType* indexType);
+
+extern const char* ToString(IndexType indexType);
+
+// Pages is a typed unit representing a multiple of wasm::PageSize. We
+// generally use pages as the unit of length when representing linear memory
+// lengths so as to avoid overflow when the specified initial or maximum pages
+// would overflow the native word size.
+//
+// Modules may specify pages up to 2^48 inclusive and so Pages is 64-bit on all
+// platforms.
+//
+// We represent byte lengths using the native word size, as it is assumed that
+// consumers of this API will only need byte lengths once it is time to
+// allocate memory, at which point the pages will be checked against the
+// implementation limits `MaxMemoryPages()` and will then be guaranteed to
+// fit in a native word.
+struct Pages {
+ private:
+  // Pages are specified by limit fields, which in general may be up to 2^48,
+  // so we must use uint64_t here.
+  uint64_t value_;
+
+ public:
+  constexpr Pages() : value_(0) {}
+  constexpr explicit Pages(uint64_t value) : value_(value) {}
+
+  // Get the wrapped page value. Only use this if you must, prefer to use or
+  // add new APIs to Page.
+  uint64_t value() const { return value_; }
+
+  // Converts from a byte length to pages, assuming that the length is an
+  // exact multiple of the page size.
+  static Pages fromByteLengthExact(size_t byteLength) {
+    MOZ_ASSERT(byteLength % PageSize == 0);
+    return Pages(byteLength / PageSize);
+  }
+
+  // Return whether the page length may overflow when converted to a byte
+  // length in the native word size.
+  bool hasByteLength() const {
+    mozilla::CheckedInt<size_t> length(value_);
+    length *= PageSize;
+    return length.isValid();
+  }
+
+  // Converts from pages to byte length in the native word size. Users must
+  // check for overflow, or be assured else-how that overflow cannot happen.
+  size_t byteLength() const {
+    mozilla::CheckedInt<size_t> length(value_);
+    length *= PageSize;
+    return length.value();
+  }
+
+  // Increment this pages by delta and return whether the resulting value
+  // did not overflow. If there is no overflow, then this is set to the
+  // resulting value.
+  bool checkedIncrement(Pages delta) {
+    mozilla::CheckedInt<uint64_t> newValue = value_;
+    newValue += delta.value_;
+    if (!newValue.isValid()) {
+      return false;
+    }
+    value_ = newValue.value();
+    return true;
+  }
+
+  // Implement pass-through comparison operators so that Pages can be compared.
+
+  bool operator==(Pages other) const { return value_ == other.value_; }
+  bool operator!=(Pages other) const { return value_ != other.value_; }
+  bool operator<=(Pages other) const { return value_ <= other.value_; }
+  bool operator<(Pages other) const { return value_ < other.value_; }
+  bool operator>=(Pages other) const { return value_ >= other.value_; }
+  bool operator>(Pages other) const { return value_ > other.value_; }
+};
+
+// The largest number of pages the application can request.
+extern Pages MaxMemoryPages(IndexType t);
+
+// The byte value of MaxMemoryPages(t).
+static inline size_t MaxMemoryBytes(IndexType t) {
+  return MaxMemoryPages(t).byteLength();
+}
+
+// A value at least as large as MaxMemoryBytes(t) representing the largest valid
+// bounds check limit on the system.  (It can be larger than MaxMemoryBytes()
+// because bounds check limits are rounded up to fit formal requirements on some
+// platforms.  Also see ComputeMappedSize().)
+extern size_t MaxMemoryBoundsCheckLimit(IndexType t);
+
+static inline uint64_t MaxMemoryLimitField(IndexType indexType) {
+  return indexType == IndexType::I32 ? MaxMemory32LimitField
+                                     : MaxMemory64LimitField;
+}
+
+// Compute the 'clamped' maximum size of a memory. See
+// 'WASM Linear Memory structure' in ArrayBufferObject.cpp for background.
+extern Pages ClampedMaxPages(IndexType t, Pages initialPages,
+                             const mozilla::Maybe<Pages>& sourceMaxPages,
+                             bool useHugeMemory);
+
+// For a given WebAssembly/asm.js 'clamped' max pages, return the number of
+// bytes to map which will necessarily be a multiple of the system page size and
+// greater than clampedMaxPages in bytes.  See "Wasm Linear Memory Structure" in
+// vm/ArrayBufferObject.cpp.
+extern size_t ComputeMappedSize(Pages clampedMaxPages);
+
+extern size_t GetMaxOffsetGuardLimit(bool hugeMemory);
+
+// Return whether the given immediate satisfies the constraints of the platform.
+extern bool IsValidBoundsCheckImmediate(uint32_t i);
+
+// Return whether the given immediate is valid on arm.
+extern bool IsValidARMImmediate(uint32_t i);
+
+// Return the next higher valid immediate that satisfies the constraints of the
+// platform.
+extern uint64_t RoundUpToNextValidBoundsCheckImmediate(uint64_t i);
+
+// Return the next higher valid immediate for arm.
+extern uint64_t RoundUpToNextValidARMImmediate(uint64_t i);
+
+#ifdef WASM_SUPPORTS_HUGE_MEMORY
+// On WASM_SUPPORTS_HUGE_MEMORY platforms, every asm.js or WebAssembly 32-bit
+// memory unconditionally allocates a huge region of virtual memory of size
+// wasm::HugeMappedSize. This allows all memory resizing to work without
+// reallocation and provides enough guard space for most offsets to be folded
+// into memory accesses.  See "Linear memory addresses and bounds checking" in
+// wasm/WasmMemory.cpp for more information.
+
+// Reserve 4GiB to support any i32 index.
+static const uint64_t HugeIndexRange = uint64_t(UINT32_MAX) + 1;
+// Reserve 32MiB to support most offset immediates. Any immediate that is over
+// this will require a bounds check to be emitted. 32MiB was chosen to
+// generously cover the max offset immediate, 20MiB, found in a corpus of wasm
+// modules.
+static const uint64_t HugeOffsetGuardLimit = 1 << 25;
+// Reserve a wasm page (64KiB) to support slop on unaligned accesses.
+static const uint64_t HugeUnalignedGuardPage = PageSize;
+
+// Compute the total memory reservation.
+static const uint64_t HugeMappedSize =
+    HugeIndexRange + HugeOffsetGuardLimit + HugeUnalignedGuardPage;
+
+// Try to keep the memory reservation aligned to the wasm page size. This
+// ensures that it's aligned to the system page size.
+static_assert(HugeMappedSize % PageSize == 0);
+
+#endif
+
+// The size of the guard page for non huge-memories.
+static const size_t GuardSize = PageSize;
+
+// The size of the guard page that included NULL pointer. Reserve a smallest
+// range for typical hardware, to catch near NULL pointer accesses, e.g.
+// for a structure fields operations.
+static const size_t NullPtrGuardSize = 4096;
+
+// Check if a range of wasm memory is within bounds, specified as byte offset
+// and length (using 32-bit indices). Omits one check by converting from
+// uint32_t to uint64_t, at which point overflow cannot occur.
+static inline bool MemoryBoundsCheck(uint32_t offset, uint32_t len,
+                                     size_t memLen) {
+  uint64_t offsetLimit = uint64_t(offset) + uint64_t(len);
+  return offsetLimit <= memLen;
+}
+
+// Check if a range of wasm memory is within bounds, specified as byte offset
+// and length (using 64-bit indices).
+static inline bool MemoryBoundsCheck(uint64_t offset, uint64_t len,
+                                     size_t memLen) {
+  uint64_t offsetLimit = offset + len;
+  bool didOverflow = offsetLimit < offset;
+  bool tooLong = memLen < offsetLimit;
+  return !didOverflow && !tooLong;
+}
+
+}  // namespace wasm
+}  // namespace js
+
+#endif  // wasm_memory_h