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Andrew Cooper
69f4633817
AFL has an alternative llvm-base instrumentation mode, which has much lower overhead than the traditional afl-gcc. One extra ability is to chose exactly where the master process gets initialised to, before being forked for testing. This point is chosen after the call to LLVMFuzzerInitialize(), so the stack isn't being remapped executable for every test. Another extra ability is to feed multiple inputs into a single test process, to reduce the number of fork() calls required overall. Two caveats are that if stdin is used for data, it must be unbuffered, and if input is passed via a command line parameter, the underlying file must be opened and closed on each iteration. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Wei Liu <wei.liu2@citrix.com>
# OVERVIEW This directory provides fuzzing targets to be run inside Google oss-fuzz infrastructure. See also https://github.com/google/oss-fuzz. # HOW IT WORKS We need to provide the source code and the rune to produce objects or archives (artefacts) from source code. These items ideally should live inside xen.git so that they can be kept up to date. The artefacts contain all the code we wish to fuzz and a function called LLVMFuzzerTestOneInput. LLVMFuzzerTestOneInput is the entry point to the code we wish to fuzz. Note that we don't produce executable programs because we don't have libFuzzEngine locally. libFuzzEngine is maintained by oss-fuzz. We also provide build script to oss-fuzz. The build script will inherit the correct compiler settings and be run in a pre-setup environment, which has libFuzzEngine installed. The build script is responsible for calling the correct Xen build rune to produce the artefacts, then link them against libFuzzEngine to produce executables, which will run in oss-fuzz infrastructure. Please refer to official oss-fuzz documents for the most up-to-date descriptions for all moving parts. # HOW TO IMPROVE THE FUZZING TARGETS Feel free to modify each fuzzing targets at will. Make sure they build by invoking make as you would build tools. To actually test the new code, you would need to run the target in standalone mode, please refer to oss-fuzz documents on how to do that. It is highly recommended that you run the new target for a while to weed out error in plumbing code to avoid false positives.