[PATCH] D12438: Build a lib/Fuzzer version for llvm-as.
Karl Schimpf via llvm-commits
llvm-commits at lists.llvm.org
Fri Aug 28 10:22:44 PDT 2015
kschimpf created this revision.
kschimpf added reviewers: kcc, filcab.
kschimpf added a subscriber: llvm-commits.
This CL is associated with a fuzzing effort to find bugs in LLVM. The
first step is to fuzz llvm-as to find potential issues in generating
IR. Both afl-fuzz and LLVM's lib/Fuzzer are being used.
This CL introduces the executable that implements the in-process
fuzzer using LLVM's lib/Fuzzer. The motivation for using lib/Fuzzer is
based on time comparisons between afl-fuzz and lib/Fuzzer. Early
results show that per-process, the lib/Fuzzer implemenation of llvm-as
(i.e. this CL) generates over 30 times the number of mutations found
by afl-fuzz, per hour runtime. The speedup is due to the removal of
overhead of forking a process, and loading the executable into memory.
I placed this under the tools directory, since it is an executable. It
is also only conditionally built if (using cmake) the flag
LLVM_USEE_SANITIZE_COVERAGE is used, so that it isn't built by
default.
http://reviews.llvm.org/D12438
Files:
tools/fuzz-llvm-as/CMakeLists.txt
tools/fuzz-llvm-as/fuzz-llvm-as.cpp
Index: tools/fuzz-llvm-as/fuzz-llvm-as.cpp
===================================================================
--- /dev/null
+++ tools/fuzz-llvm-as/fuzz-llvm-as.cpp
@@ -0,0 +1,74 @@
+//===--- fuzz-llvm-as.cpp - Fuzzer for llvm-as using lib/Fuzzer -----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Build tool to fuzz the LLVM assembler (llvm-as) using
+// lib/Fuzzer. The main reason for using this tool is that it is much
+// faster than using afl-fuzz, since it is run in-process.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/SourceMgr.h"
+
+#include <csetjmp>
+
+using namespace llvm;
+
+static jmp_buf JmpBuf;
+
+namespace {
+
+void MyFatalErrorHandler(void *user_data, const std::string& reason,
+ bool gen_crash_diag) {
+ // Don't bother printing reason, just return to the test function,
+ // since a fatal error represents a successful parse (i.e. it correctly
+ // terminated with an error message to the user).
+ longjmp(JmpBuf, 1);
+}
+
+static bool InstalledHandler = false;
+
+} // end of anonymous namespace
+
+extern "C" void LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+
+ // Allocate space for locals before setjmp so that memory can be collected
+ // if parse exits prematurely (via longjmp).
+ StringRef Input((const char *)Data, Size);
+ // Note: We need to create a buffer to add a null terminator to the
+ // end of the input string. The parser assumes that the string
+ // parsed is always null terminated.
+ std::unique_ptr<MemoryBuffer> MemBuf = MemoryBuffer::getMemBufferCopy(Input);
+ SMDiagnostic Err;
+ LLVMContext &Context = getGlobalContext();
+ std::unique_ptr<Module> M;
+
+ if (setjmp(JmpBuf))
+ // If reached, we have returned with non-zero status, so exit.
+ return;
+
+ if (!InstalledHandler) {
+ llvm::install_fatal_error_handler(::MyFatalErrorHandler, nullptr);
+ InstalledHandler = true;
+ }
+
+ M = parseAssembly(MemBuf->getMemBufferRef(), Err, Context);
+
+ if (!M.get())
+ return;
+
+ verifyModule(*M.get());
+}
Index: tools/fuzz-llvm-as/CMakeLists.txt
===================================================================
--- /dev/null
+++ tools/fuzz-llvm-as/CMakeLists.txt
@@ -0,0 +1,13 @@
+if( LLVM_USE_SANITIZE_COVERAGE )
+ set(LLVM_LINK_COMPONENTS
+ AsmParser
+ BitWriter
+ Core
+ Support
+ )
+ add_llvm_tool(fuzz-llvm-as
+ fuzz-llvm-as.cpp)
+ target_link_libraries(fuzz-llvm-as
+ LLVMFuzzer
+ )
+endif()
-------------- next part --------------
A non-text attachment was scrubbed...
Name: D12438.33439.patch
Type: text/x-patch
Size: 3106 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20150828/9163d412/attachment-0001.bin>
More information about the llvm-commits
mailing list