diff options
Diffstat (limited to 'llvm_mode')
| -rw-r--r-- | llvm_mode/README.lto.md | 34 | ||||
| -rw-r--r-- | llvm_mode/afl-clang-fast.c | 21 |
2 files changed, 47 insertions, 8 deletions
diff --git a/llvm_mode/README.lto.md b/llvm_mode/README.lto.md index 4641fa89..967a31aa 100644 --- a/llvm_mode/README.lto.md +++ b/llvm_mode/README.lto.md @@ -125,10 +125,9 @@ NOTE: some targets also need to set the linker, try both `afl-clang-lto` and ## AUTODICTIONARY feature -Setting `AFL_LLVM_LTO_AUTODICTIONARY` will generate a dictionary in the -target binary based on string compare and memory compare functions. -afl-fuzz will automatically get these transmitted when starting to fuzz. -This improves coverage on a lot of targets. +While compiling, automatically a dictionary based on string comparisons is +generated put into the target binary. This dictionary is transfered to afl-fuzz +on start. This improves coverage statistically by 5-10% :) ## Fixed memory map @@ -147,6 +146,8 @@ Some targets are difficult because the configure script does unusual stuff that is unexpected for afl. See the next chapter `Potential issues` how to solve these. +### Example: ffmpeg + An example of a hard to solve target is ffmpeg. Here is how to successfully instrument it: @@ -186,6 +187,31 @@ instrument it: 4. Then type make, wait for a long time and you are done :) +### Example: WebKit jsc + +Building jsc is difficult as the build script has bugs. + +1. checkout Webkit: +``` +svn checkout https://svn.webkit.org/repository/webkit/trunk WebKit +cd WebKit +``` + +2. Fix the build environment: +``` +mkdir -p WebKitBuild/Release +cd WebKitBuild/Release +ln -s ../../../../../usr/bin/llvm-ar-11 llvm-ar-11 +ln -s ../../../../../usr/bin/llvm-ranlib-11 llvm-ranlib-11 +cd ../.. +``` + +3. Build :) + +``` +Tools/Scripts/build-jsc --jsc-only --cli --cmakeargs="-DCMAKE_AR='llvm-ar-11' -DCMAKE_RANLIB='llvm-ranlib-11' -DCMAKE_VERBOSE_MAKEFILE:BOOL=ON -DCMAKE_CC_FLAGS='-O3 -lrt' -DCMAKE_CXX_FLAGS='-O3 -lrt' -DIMPORTED_LOCATION='/lib/x86_64-linux-gnu/' -DCMAKE_CC=afl-clang-lto -DCMAKE_CXX=afl-clang-lto++ -DENABLE_STATIC_JSC=ON" +``` + ## Potential issues ### compiling libraries fails diff --git a/llvm_mode/afl-clang-fast.c b/llvm_mode/afl-clang-fast.c index 8823b6a5..4d01e740 100644 --- a/llvm_mode/afl-clang-fast.c +++ b/llvm_mode/afl-clang-fast.c @@ -768,9 +768,19 @@ int main(int argc, char **argv, char **envp) { #if LLVM_VERSION_MAJOR <= 6 instrument_mode = INSTRUMENT_AFL; #else - if (getenv("AFL_LLVM_INSTRUMENT_FILE") || getenv("AFL_LLVM_WHITELIST")) + if (getenv("AFL_LLVM_INSTRUMENT_FILE") || getenv("AFL_LLVM_WHITELIST")) { + instrument_mode = INSTRUMENT_AFL; - else + WARNF( + "switching to classic instrumentation because " + "AFL_LLVM_INSTRUMENT_FILE does not work with PCGUARD. Use " + "-fsanitize-coverage-allowlist=allowlist.txt if you want to use " + "PCGUARD. See " + "https://clang.llvm.org/docs/" + "SanitizerCoverage.html#partially-disabling-instrumentation"); + + } else + instrument_mode = INSTRUMENT_PCGUARD; #endif @@ -818,9 +828,12 @@ int main(int argc, char **argv, char **envp) { if (instrument_mode == INSTRUMENT_PCGUARD && (getenv("AFL_LLVM_INSTRUMENT_FILE") || getenv("AFL_LLVM_WHITELIST"))) - WARNF( + FATAL( "Instrumentation type PCGUARD does not support " - "AFL_LLVM_INSTRUMENT_FILE!"); + "AFL_LLVM_INSTRUMENT_FILE! Use " + "-fsanitize-coverage-allowlist=allowlist.txt instead, see " + "https://clang.llvm.org/docs/" + "SanitizerCoverage.html#partially-disabling-instrumentation"); if (argc < 2 || strcmp(argv[1], "-h") == 0) { |