We have several scripts that help build reproducers, but no documentation for how they should be used. Add some documentation
Signed-off-by: Alexander Bulekov <alx...@bu.edu> --- docs/devel/fuzzing.rst | 45 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) diff --git a/docs/devel/fuzzing.rst b/docs/devel/fuzzing.rst index 97797c4f8c..025fb0c19b 100644 --- a/docs/devel/fuzzing.rst +++ b/docs/devel/fuzzing.rst @@ -210,6 +210,51 @@ Build details: - The script responsible for building the fuzzers can be found in the QEMU source tree at ``scripts/oss-fuzz/build.sh`` +Building Crash Reproducers +----------------------------------------- +When we find a crash, we should try to create an independent reproducer, that +can be used on a non-fuzzer build of QEMU. This filters out any potential +false-positives, and improves the debugging experience for developers. +Here are the steps for building a reproducer for a crash found by the +generic-fuzz target. + - Ensure the crash reproduces:: + qemu-fuzz-i386 --fuzz-target... ./crash-... + + - Gather the QTest output for the crash:: + QEMU_FUZZ_TIMEOUT=0 QTEST_LOG=1 FUZZ_SERIALIZE_QTEST=1 \ + qemu-fuzz-i386 --fuzz-target... ./crash-... &> /tmp/trace + + - Reorder and clean-up the resulting trace:: + scripts/oss-fuzz/reorder_fuzzer_qtest_trace.py /tmp/trace > /tmp/reproducer + + - Get the arguments needed to start qemu, and provide a path to qemu:: + less /tmp/trace # The args should be logged at the top of this file + export QEMU_ARGS="-machine ..." + export QEMU_PATH="path/to/qemu-system" + + - Ensure the crash reproduces in qemu-system:: + $QEMU_PATH $QEMU_ARGS -qtest stdio < /tmp/reproducer + + - From the crash output, obtain some string that identifies the crash. This + can be a line in the stack-trace, for example:: + export CRASH_TOKEN="hw/usb/hcd-xhci.c:1865" + + - Minimize the reproducer:: + scripts/oss-fuzz/minimize_qtest_trace.py -M1 -M2 \ + /tmp/reproducer /tmp/reproducer-minimized + + - Confirm that the minimized reproducer still crashes:: + $QEMU_PATH $QEMU_ARGS -qtest stdio < /tmp/reproducer-minimized + + - Create a one-liner reproducer that can be sent over email:: + ./scripts/oss-fuzz/output_reproducer.py -bash /tmp/reproducer-minimized + + - Output the C source code for a test case that will reproduce the bug :: + ./scripts/oss-fuzz/output_reproducer.py -owner "John Smith <j...@smith.com>"\ + -name "test_function_name" /tmp/reproducer-minimized + + - Report the bug and send a patch with the C reproducer upstream + Implementation Details / Fuzzer Lifecycle ----------------------------------------- -- 2.28.0