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-exception 6// 7//===----------------------------------------------------------------------===// 8// Extra coverage counters defined by user code for Windows. 9//===----------------------------------------------------------------------===// 10 11#include "FuzzerPlatform.h" 12#include <cstdint> 13 14#if LIBFUZZER_WINDOWS 15#include <windows.h> 16 17namespace fuzzer { 18 19// 20// The __start___libfuzzer_extra_counters variable is align 16, size 16 to 21// ensure the padding between it and the next variable in this section (either 22// __libfuzzer_extra_counters or __stop___libfuzzer_extra_counters) will be 23// located at (__start___libfuzzer_extra_counters + 24// sizeof(__start___libfuzzer_extra_counters)). Otherwise, the calculation of 25// (stop - (start + sizeof(start))) might be skewed. 26// 27// The section name, __libfuzzer_extra_countaaa ends with "aaa", so it sorts 28// before __libfuzzer_extra_counters alphabetically. We want the start symbol to 29// 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_t 34 __start___libfuzzer_extra_counters[16] = {0}; 35 36// 37// Example of what the user-supplied counters should look like. First, the 38// pragma to create the section name. It will fall alphabetically between 39// ".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 of 43// __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 it 55// sorts after __libfuzzer_extra_counters alphabetically. We want the stop 56// symbol to be placed in the section just after the user supplied counters (if 57// present). Align to 1 so there isn't any padding placed between this and the 58// previous variable. 59// 60#pragma section(".data$__libfuzzer_extra_countzzz") 61ATTRIBUTE_ALIGNED(1) 62__declspec(allocate(".data$__libfuzzer_extra_countzzz")) uint8_t 63 __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_ALL 73void ClearExtraCounters() { 74 uint8_t *Beg = ExtraCountersBegin(); 75 SecureZeroMemory(Beg, ExtraCountersEnd() - Beg); 76} 77 78} // namespace fuzzer 79 80#endif 81