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Diffstat (limited to 'instrumentation/README.lto.md')
| -rw-r--r-- | instrumentation/README.lto.md | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/instrumentation/README.lto.md b/instrumentation/README.lto.md index 38252308..6174cdc0 100644 --- a/instrumentation/README.lto.md +++ b/instrumentation/README.lto.md @@ -60,12 +60,12 @@ AUTODICTIONARY: 11 strings found ## Getting llvm 11+ -### Installing llvm version 11 +### Installing llvm version 11 or 12 -llvm 11 should be available in all current Linux repositories. +llvm 11 or even 12 should be available in all current Linux repositories. If you use an outdated Linux distribution read the next section. -### Installing llvm from the llvm repository (version 12) +### Installing llvm from the llvm repository (version 12+) Installing the llvm snapshot builds is easy and mostly painless: @@ -85,7 +85,7 @@ apt-get install -y clang-12 clang-tools-12 libc++1-12 libc++-12-dev \ libomp5-12 lld-12 lldb-12 llvm-12 llvm-12-dev llvm-12-runtime llvm-12-tools ``` -### Building llvm yourself (version 12) +### Building llvm yourself (version 12+) Building llvm from github takes quite some long time and is not painless: ```sh @@ -146,22 +146,22 @@ afl-clang-lto instead of shared libraries! To make instrumented shared libraries work with afl-clang-lto you have to do quite some extra steps. -Every shared library you want to instrument has to be individually compiled- +Every shared library you want to instrument has to be individually compiled. The environment variable `AFL_LLVM_LTO_DONTWRITEID=1` has to be set during compilation. Additionally the environment variable `AFL_LLVM_LTO_STARTID` has to be set to -the combined edge values of all previous compiled instrumented shared +the added edge count values of all previous compiled instrumented shared libraries for that target. E.g. for the first shared library this would be `AFL_LLVM_LTO_STARTID=0` and afl-clang-lto will then report how many edges have been instrumented (let's say it reported 1000 instrumented edges). The second shared library then has to be set to that value -(`AFL_LLVM_LTO_STARTID=1000` in our example), the third to all previous -combined, etc. +(`AFL_LLVM_LTO_STARTID=1000` in our example), for the third to all previous +counts added, etc. The final program compilation step then may *not* have `AFL_LLVM_LTO_DONTWRITEID` -set, and `AFL_LLVM_LTO_STARTID` must be set to all combined edges of all shared -libaries it will be linked to. +set, and `AFL_LLVM_LTO_STARTID` must be set to all edge counts added of all shared +libraries it will be linked to. This is quite some hands-on work, so better stay away from instrumenting shared libraries :-) |