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envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=40.107.68.136; envelope-from=alxndr@bu.edu; helo=NAM04-BN3-obe.outbound.protection.outlook.com X-Spam_score_int: -8 X-Spam_score: -0.9 X-Spam_bar: / X-Spam_report: (-0.9 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, HK_RANDOM_ENVFROM=0.001, HK_RANDOM_FROM=1, MSGID_FROM_MTA_HEADER=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Darren Kenny , Alexander Bulekov Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @bushare.onmicrosoft.com) Content-Type: text/plain; charset="utf-8" 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 Reviewed-by: Darren Kenny --- 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`` =20 +Building Crash Reproducers +----------------------------------------- +When we find a crash, we should try to create an independent reproducer, t= hat +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=3D0 QTEST_LOG=3D1 FUZZ_SERIALIZE_QTEST=3D1 \ + 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/reprod= ucer + + - 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=3D"-machine ..." + export QEMU_PATH=3D"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. Th= is + can be a line in the stack-trace, for example:: + export CRASH_TOKEN=3D"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 "\ + -name "test_function_name" /tmp/reproducer-minimized + + - Report the bug and send a patch with the C reproducer upstream + Implementation Details / Fuzzer Lifecycle ----------------------------------------- =20 --=20 2.27.0