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6708186c91
Attempting to build a standalone libFuzzer in Fuchsia's default toolchain for the purpose of cross-compiling the unit tests revealed a number of not-quite-proper type conversions. Fuchsia's toolchain include `-std=c++17` and `-Werror`, among others, leading to many errors like `-Wshorten-64-to-32`, `-Wimplicit-float-conversion`, etc. Most of these have been addressed by simply making the conversion explicit with a `static_cast`. These typically fell into one of two categories: 1) conversions between types where high precision isn't critical, e.g. the "energy" calculations for `InputInfo`, and 2) conversions where the values will never reach the bits being truncated, e.g. `DftTimeInSeconds` is not going to exceed 136 years. The major exception to this is the number of features: there are several places that treat features as `size_t`, and others as `uint32_t`. This change makes the decision to cap the features at 32 bits. The maximum value of a feature as produced by `TracePC::CollectFeatures` is roughly: (NumPCsInPCTables + ValueBitMap::kMapSizeInBits + ExtraCountersBegin() - ExtraCountersEnd() + log2(SIZE_MAX)) * 8 It's conceivable for extremely large targets and/or extra counters that this limit could be reached. This shouldn't break fuzzing, but it will cause certain features to collide and lower the fuzzers overall precision. To address this, this change adds a warning to TracePC::PrintModuleInfo about excessive feature size if it is detected, and recommends refactoring the fuzzer into several smaller ones. Reviewed By: morehouse Differential Revision: https://reviews.llvm.org/D97992
35 lines
1.2 KiB
C++
35 lines
1.2 KiB
C++
//===- FuzzerBuiltins.h - Internal header for builtins ----------*- C++ -* ===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// Wrapper functions and marcos around builtin functions.
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_FUZZER_BUILTINS_H
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#define LLVM_FUZZER_BUILTINS_H
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#include "FuzzerPlatform.h"
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#if !LIBFUZZER_MSVC
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#include <cstdint>
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#define GET_CALLER_PC() __builtin_return_address(0)
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namespace fuzzer {
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inline uint8_t Bswap(uint8_t x) { return x; }
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inline uint16_t Bswap(uint16_t x) { return __builtin_bswap16(x); }
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inline uint32_t Bswap(uint32_t x) { return __builtin_bswap32(x); }
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inline uint64_t Bswap(uint64_t x) { return __builtin_bswap64(x); }
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inline uint32_t Clzll(unsigned long long X) { return __builtin_clzll(X); }
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inline int Popcountll(unsigned long long X) { return __builtin_popcountll(X); }
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} // namespace fuzzer
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#endif // !LIBFUZZER_MSVC
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#endif // LLVM_FUZZER_BUILTINS_H
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