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b=J/MsqyyNaO0urdVqtcjyT038z6oMqDOT9u96D31KGtzNLpGVjj0W3fb8be33ZV/eC1+S20 gyBx3yEkjeR0PgRwAywm02aip/RZ2mvaf7XDxVYOnkTfGbh+/ToUsynJEQbRzC8dJXVV8D T4+wlZ/QspmO8DUjDn+CYpi7wbtzHA4= X-MC-Unique: IAa5m0N6MwaEzOG1UUA1ZA-1 From: Thomas Huth To: peter.maydell@linaro.org, qemu-devel@nongnu.org Subject: [PULL 07/10] docs/fuzz: add instructions for generating a coverage report Date: Tue, 21 Jul 2020 10:10:52 +0200 Message-Id: <20200721081055.14073-8-thuth@redhat.com> In-Reply-To: <20200721081055.14073-1-thuth@redhat.com> References: <20200721081055.14073-1-thuth@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=205.139.110.61; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/21 01:26:46 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -40 X-Spam_score: -4.1 X-Spam_bar: ---- X-Spam_report: (-4.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham 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: Alexander Bulekov Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: pass (identity @redhat.com) Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Alexander Bulekov Signed-off-by: Alexander Bulekov Message-Id: <20200706195534.14962-5-alxndr@bu.edu> [thuth: Replaced --enable-sanitizers with --enable-fuzzing] Signed-off-by: Thomas Huth --- docs/devel/fuzzing.txt | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/docs/devel/fuzzing.txt b/docs/devel/fuzzing.txt index 6d18115239..96d71c94d7 100644 --- a/docs/devel/fuzzing.txt +++ b/docs/devel/fuzzing.txt @@ -85,6 +85,25 @@ better coverage performance, depending on the target. Note that libFuzzer's exact behavior will depend on the version of clang and libFuzzer used to build the device fuzzers. =20 +=3D=3D Generating Coverage Reports =3D=3D +Code coverage is a crucial metric for evaluating a fuzzer's performance. +libFuzzer's output provides a "cov: " column that provides a total number = of +unique blocks/edges covered. To examine coverage on a line-by-line basis we +can use Clang coverage: + + 1. Configure libFuzzer to store a corpus of all interesting inputs (see + CORPUS_DIR above) + 2. ./configure the QEMU build with: + --enable-fuzzing \ + --extra-cflags=3D"-fprofile-instr-generate -fcoverage-mapping" + 3. Re-run the fuzzer. Specify $CORPUS_DIR/* as an argument, telling libfu= zzer + to execute all of the inputs in $CORPUS_DIR and exit. Once the process + exits, you should find a file, "default.profraw" in the working direct= ory. + 4. Execute these commands to generate a detailed HTML coverage-report: + llvm-profdata merge -output=3Ddefault.profdata default.profraw + llvm-cov show ./path/to/qemu-fuzz-i386 -instr-profile=3Ddefault.profdata \ + --format html -output-dir=3D/path/to/output/report + =3D=3D Adding a new fuzzer =3D=3D Coverage over virtual devices can be improved by adding additional fuzzers. Fuzzers are kept in tests/qtest/fuzz/ and should be added to --=20 2.18.1