From 996986bed5f2dd97a3d76f584d8eddc1203f8396 Mon Sep 17 00:00:00 2001 From: vanhauser-thc Date: Sat, 5 Sep 2020 12:11:48 +0200 Subject: first batch of changes --- instrumentation/README.instrim.md | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 instrumentation/README.instrim.md (limited to 'instrumentation/README.instrim.md') diff --git a/instrumentation/README.instrim.md b/instrumentation/README.instrim.md new file mode 100644 index 00000000..99f6477a --- /dev/null +++ b/instrumentation/README.instrim.md @@ -0,0 +1,30 @@ +# InsTrim + +InsTrim: Lightweight Instrumentation for Coverage-guided Fuzzing + +## Introduction + +InsTrim is the work of Chin-Chia Hsu, Che-Yu Wu, Hsu-Chun Hsiao and Shih-Kun Huang. + +It uses a CFG (call flow graph) and markers to instrument just what +is necessary in the binary (ie less than llvm_mode). As a result the binary is +about 10-15% faster compared to normal llvm_mode however with some coverage loss. +It requires at least llvm version 3.8.0 to build. +If you have LLVM 7+ we recommend PCGUARD instead. + +## Usage + +Set the environment variable `AFL_LLVM_INSTRUMENT=CFG` or `AFL_LLVM_INSTRIM=1` +during compilation of the target. + +There is also special mode which instruments loops in a way so that +afl-fuzz can see which loop path has been selected but not being able to +see how often the loop has been rerun. +This again is a tradeoff for speed for less path information. +To enable this mode set `AFL_LLVM_INSTRIM_LOOPHEAD=1`. + +## Background + +The paper from Chin-Chia Hsu, Che-Yu Wu, Hsu-Chun Hsiao and Shih-Kun Huang: +[InsTrim: Lightweight Instrumentation for Coverage-guided Fuzzing] +(https://www.ndss-symposium.org/wp-content/uploads/2018/07/bar2018_14_Hsu_paper.pdf) -- cgit 1.4.1