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| -rw-r--r-- | qemu_mode/README.md | 33 | ||||
| -rwxr-xr-x | qemu_mode/build_qemu_support.sh | 4 |
2 files changed, 33 insertions, 4 deletions
diff --git a/qemu_mode/README.md b/qemu_mode/README.md index 92038737..b78eb297 100644 --- a/qemu_mode/README.md +++ b/qemu_mode/README.md @@ -193,12 +193,39 @@ Comparative measurements of execution speed or instrumentation coverage will be fairly meaningless if the optimization levels or instrumentation scopes don't match. -## 12) Other features +## 12) Coverage information + +Coverage information about a run of a target binary can be obtained using a +dedicated QEMU user mode plugin enabled at runtime: the `drcov.c` plugin +collects coverage information from the target binary and writes it in the Drcov +format. This file can then be loaded using tools such as +[lighthouse](https://github.com/gaasedelen/lighthouse), +[lightkeeper](https://github.com/WorksButNotTested/lightkeeper) or +[Cartographer](https://github.com/nccgroup/Cartographer). + +To compile the QEMU TCG plugins, run the following command from the `qemuafl` +directory: + +``` +make plugins +``` + +Plugins can be loaded using either the `QEMU_PLUGIN` environment variable or +using the `-plugin` option. For example: + +``` +afl-qemu-trace -plugin qemuafl/build/contrib/plugins/libdrcov.so,arg=filename=/tmp/target.drcov.trace <target> <args> +``` + +This would execute the target binary with the provided arguments and, once done, +would write coverage information at `/tmp/target.drcov.trace`. + +## 13) Other features With `AFL_QEMU_FORCE_DFL`, you force QEMU to ignore the registered signal handlers of the target. -## 13) Gotchas, feedback, bugs +## 14) Gotchas, feedback, bugs If you need to fix up checksums or do other cleanups on mutated test cases, see `afl_custom_post_process` in custom_mutators/examples/example.c for a viable @@ -217,7 +244,7 @@ program may be utilizing. In particular, it does not appear to have full support for AVX2/FMA3. Using binaries for older CPUs or recompiling them with `-march=core2`, can help. -## 14) Alternatives: static rewriting +## 15) Alternatives: static rewriting Statically rewriting binaries just once, instead of attempting to translate them at run time, can be a faster alternative. That said, static rewriting is fraught diff --git a/qemu_mode/build_qemu_support.sh b/qemu_mode/build_qemu_support.sh index f59cba78..3f8a88f2 100755 --- a/qemu_mode/build_qemu_support.sh +++ b/qemu_mode/build_qemu_support.sh @@ -132,7 +132,10 @@ echo "Building for CPU target $CPU_TARGET" # --enable-pie seems to give a couple of exec's a second performance # improvement, much to my surprise. Not sure how universal this is.. +# --enable-plugins allows loading TCG plugins at runtime, for example to obtain +# coverage information, and does not seem to negatively impact performance QEMU_CONF_FLAGS=" \ + --enable-plugins \ --audio-drv-list= \ --disable-blobs \ --disable-bochs \ @@ -162,7 +165,6 @@ QEMU_CONF_FLAGS=" \ --disable-numa \ --disable-opengl \ --disable-parallels \ - --disable-plugins \ --disable-qcow1 \ --disable-qed \ --disable-rbd \ |