compiler-rt/test/fuzzer/MsanCustomMutator.cpp

   1 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   2 // See https://llvm.org/LICENSE.txt for license information.
   3 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   4
   5 // Triggers the bug described here:
   6 // https://github.com/google/oss-fuzz/issues/4605
   7 //
   8 // Tests that custom mutators do not cause MSan false positives.  We are careful
   9 // to use every parameter to ensure none cause false positives.
  10
  11 #include <algorithm>
  12 #include <cstddef>
  13 #include <cstdint>
  14 #include <cstdio>
  15 #include <cstring>
  16
  17 extern "C" {
  18
  19 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) { return 0; }
  20
  21 size_t LLVMFuzzerCustomMutator(uint8_t *Data, size_t Size, size_t MaxSize,
  22                                unsigned int Seed) {
  23   if (Seed == 7)
  24     return 0;
  25   if (MaxSize == 0)
  26     return 0;
  27   for (size_t I = 0; I < Size; ++I) {
  28     if (Data[I] == 42) {
  29       printf("BINGO\n");
  30     }
  31   }
  32   return Size;
  33 }
  34
  35 size_t LLVMFuzzerCustomCrossOver(
  36     const uint8_t *Data1, size_t Size1, const uint8_t *Data2, size_t Size2,
  37     uint8_t *Out, size_t MaxOutSize, unsigned int Seed) {
  38   if (Seed == 7)
  39     return 0;
  40   size_t I = 0;
  41   for (; I < Size1 && I < Size2 && I < MaxOutSize; ++I) {
  42     Out[I] = std::min(Data1[I], Data2[I]);
  43   }
  44   return I;
  45 }
  46
  47 } // extern "C"