1d3c4975be
If we can read an object's Map pointer but not any data from the Map itself, we may still be able to accurately describe the object's type if the Map pointer matches one of the known Maps from the snapshot. GetObjectProperties uses that data in one of two ways: - If it is sure that the Map pointer matches a known Map, then it uses the type from that Map and continues as if it read the type normally. - If the Map pointer is at the right offset within a heap page to match a known Map, but the caller didn't provide the addresses of the first pages in Map space or read-only space, then the type of that Map is just a guess and gets returned in a separate array. This gives the caller the opportunity to present guessed types to the user, and perhaps call again using the guessed type as the type hint. Bug: v8:9376 Change-Id: I187f67b77e76699863a14534a9d635b79f654124 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1787986 Commit-Queue: Seth Brenith <seth.brenith@microsoft.com> Reviewed-by: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Michael Achenbach <machenbach@chromium.org> Reviewed-by: Tobias Tebbi <tebbi@chromium.org> Cr-Commit-Position: refs/heads/master@{#63908}
68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
// Copyright 2019 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_TOOLS_DEBUG_HELPER_HEAP_CONSTANTS_H_
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#define V8_TOOLS_DEBUG_HELPER_HEAP_CONSTANTS_H_
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#include <cstdint>
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#include <string>
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#include <vector>
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#include "debug-helper.h"
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#include "src/objects/instance-type.h"
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namespace d = v8::debug_helper;
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namespace v8_debug_helper_internal {
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// ===== Functions generated by gen-heap-constants.py: =========================
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// Returns the name of a known object, given its offset within the first page of
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// the space, or empty string on failure.
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std::string FindKnownObjectInOldSpace(uintptr_t offset);
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std::string FindKnownObjectInReadOnlySpace(uintptr_t offset);
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std::string FindKnownObjectInMapSpace(uintptr_t offset);
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// In builds with pointer compression enabled, sets the *_first_page members in
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// the HeapAddresses object. In other builds, does nothing.
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void FillInUnknownHeapAddresses(d::HeapAddresses* heap_addresses,
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uintptr_t any_uncompressed_ptr);
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// Returns the instance type for the known Map, given its offset within the
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// first page of the space, or empty string on failure.
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int FindKnownMapInstanceTypeInMapSpace(uintptr_t offset);
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int FindKnownMapInstanceTypeInReadOnlySpace(uintptr_t offset);
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// ===== End of generated functions. ===========================================
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// Returns a descriptive string if the given address matches a known object, or
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// an empty string otherwise.
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std::string FindKnownObject(uintptr_t address,
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const d::HeapAddresses& heap_addresses);
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struct KnownInstanceType {
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enum class Confidence {
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kLow,
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kHigh,
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};
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KnownInstanceType() : confidence(Confidence::kLow) {}
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KnownInstanceType(int type) : KnownInstanceType() {
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if (type >= 0) {
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confidence = Confidence::kHigh;
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types.push_back(static_cast<v8::internal::InstanceType>(type));
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}
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}
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Confidence confidence;
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std::vector<v8::internal::InstanceType> types;
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};
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// Returns information about the instance type of the Map at the given address,
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// based on the list of known Maps.
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KnownInstanceType FindKnownMapInstanceType(
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uintptr_t address, const d::HeapAddresses& heap_addresses);
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} // namespace v8_debug_helper_internal
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#endif
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