[compiler-rt] 15f1d5d - [libFuzzer] Add INFO output when LLVMFuzzerCustomMutator is found.

[Max Moroz via llvm-commits]

Author: Max Moroz
Date: 2020-01-22T12:56:16-08:00
New Revision: 15f1d5d14425528540e1cc4aa776b195a2e1e7e0

URL: https://github.com/llvm/llvm-project/commit/15f1d5d14425528540e1cc4aa776b195a2e1e7e0
DIFF: https://github.com/llvm/llvm-project/commit/15f1d5d14425528540e1cc4aa776b195a2e1e7e0.diff

LOG: [libFuzzer] Add INFO output when LLVMFuzzerCustomMutator is found.

Summary:
there is an ongoing work on interchangeable custom mutators
(https://github.com/google/clusterfuzz/pull/1333/files#r367706283)
and having some sort of signalling from libFuzzer that it has loaded
a custom mutator would be helpful.

The initial idea was to make the mutator to print something, but given
the anticipated variety of different mutators, it does not seem possible
to make all of them print the same message to signal their execution.

Reviewers: kcc, metzman

Reviewed By: metzman

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D73136

Added: 
    

Modified: 
    compiler-rt/lib/fuzzer/FuzzerDriver.cpp
    compiler-rt/test/fuzzer/fuzzer-custommutator.test

Removed: 
    


################################################################################
diff  --git a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
index dd3cab0ee8d2..0063cde4820d 100644
--- a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
@@ -195,8 +195,11 @@ static void ParseFlags(const Vector<std::string> &Args,
   }
 
   // Disable len_control by default, if LLVMFuzzerCustomMutator is used.
-  if (EF->LLVMFuzzerCustomMutator)
+  if (EF->LLVMFuzzerCustomMutator) {
     Flags.len_control = 0;
+    Printf("INFO: found LLVMFuzzerCustomMutator (%p). "
+           "Disabling -len_control by default.\n", EF->LLVMFuzzerCustomMutator);
+  }
 
   Inputs = new Vector<std::string>;
   for (size_t A = 1; A < Args.size(); A++) {

diff  --git a/compiler-rt/test/fuzzer/fuzzer-custommutator.test b/compiler-rt/test/fuzzer/fuzzer-custommutator.test
index 66fd888c97c0..87e69a0d8cf3 100644
--- a/compiler-rt/test/fuzzer/fuzzer-custommutator.test
+++ b/compiler-rt/test/fuzzer/fuzzer-custommutator.test
@@ -1,11 +1,13 @@
 RUN: %cpp_compiler %S/CustomMutatorTest.cpp -o %t-CustomMutatorTest
 RUN: not %run %t-CustomMutatorTest 2>&1 | FileCheck %s --check-prefix=LLVMFuzzerCustomMutator
+LLVMFuzzerCustomMutator: INFO: found LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutator: In LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutator: {{.*}} lim: 4096 {{.*}}
 LLVMFuzzerCustomMutator: BINGO
 
 # len_control is disabled for custom mutators by default, test that it can be enabled.
 RUN: not %run %t-CustomMutatorTest -len_control=100 2>&1 | FileCheck %s --check-prefix=LLVMFuzzerCustomMutatorWithLenControl
+LLVMFuzzerCustomMutatorWithLenControl: INFO: found LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutatorWithLenControl: In LLVMFuzzerCustomMutator
 LLVMFuzzerCustomMutatorWithLenControl: {{.*}} lim: {{[1-9][0-9]?}} {{.*}}
 LLVMFuzzerCustomMutatorWithLenControl: BINGO