81 lines · cpp
1//===- FuzzerExtraCountersWindows.cpp - Extra coverage counters for Win32 -===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8// Extra coverage counters defined by user code for Windows.9//===----------------------------------------------------------------------===//10 11#include "FuzzerPlatform.h"12#include <cstdint>13 14#if LIBFUZZER_WINDOWS15#include <windows.h>16 17namespace fuzzer {18 19//20// The __start___libfuzzer_extra_counters variable is align 16, size 16 to21// ensure the padding between it and the next variable in this section (either22// __libfuzzer_extra_counters or __stop___libfuzzer_extra_counters) will be23// located at (__start___libfuzzer_extra_counters +24// sizeof(__start___libfuzzer_extra_counters)). Otherwise, the calculation of25// (stop - (start + sizeof(start))) might be skewed.26//27// The section name, __libfuzzer_extra_countaaa ends with "aaa", so it sorts28// before __libfuzzer_extra_counters alphabetically. We want the start symbol to29// be placed in the section just before the user supplied counters (if present).30//31#pragma section(".data$__libfuzzer_extra_countaaa")32ATTRIBUTE_ALIGNED(16)33__declspec(allocate(".data$__libfuzzer_extra_countaaa")) uint8_t34 __start___libfuzzer_extra_counters[16] = {0};35 36//37// Example of what the user-supplied counters should look like. First, the38// pragma to create the section name. It will fall alphabetically between39// ".data$__libfuzzer_extra_countaaa" and ".data$__libfuzzer_extra_countzzz".40// Next, the declspec to allocate the variable inside the specified section.41// Finally, some array, struct, whatever that is used to track the counter data.42// The size of this variable is computed at runtime by finding the difference of43// __stop___libfuzzer_extra_counters and __start___libfuzzer_extra_counters +44// sizeof(__start___libfuzzer_extra_counters).45//46 47//48// #pragma section(".data$__libfuzzer_extra_counters")49// __declspec(allocate(".data$__libfuzzer_extra_counters"))50// uint8_t any_name_variable[64 * 1024];51//52 53//54// Here, the section name, __libfuzzer_extra_countzzz ends with "zzz", so it55// sorts after __libfuzzer_extra_counters alphabetically. We want the stop56// symbol to be placed in the section just after the user supplied counters (if57// present). Align to 1 so there isn't any padding placed between this and the58// previous variable.59//60#pragma section(".data$__libfuzzer_extra_countzzz")61ATTRIBUTE_ALIGNED(1)62__declspec(allocate(".data$__libfuzzer_extra_countzzz")) uint8_t63 __stop___libfuzzer_extra_counters = 0;64 65uint8_t *ExtraCountersBegin() {66 return __start___libfuzzer_extra_counters +67 sizeof(__start___libfuzzer_extra_counters);68}69 70uint8_t *ExtraCountersEnd() { return &__stop___libfuzzer_extra_counters; }71 72ATTRIBUTE_NO_SANITIZE_ALL73void ClearExtraCounters() {74 uint8_t *Beg = ExtraCountersBegin();75 SecureZeroMemory(Beg, ExtraCountersEnd() - Beg);76}77 78} // namespace fuzzer79 80#endif81