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[95.90.237.182]) by smtp.gmail.com with ESMTPSA id q193sm84991wme.8.2019.06.25.12.42.43 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Tue, 25 Jun 2019 12:42:43 -0700 (PDT) From: Krzesimir Nowak To: netdev@vger.kernel.org Cc: Alban Crequy , =?UTF-8?q?Iago=20L=C3=B3pez=20Galeiras?= , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, Krzesimir Nowak Subject: [bpf-next v2 00/10] Test the 32bit narrow reads Date: Tue, 25 Jun 2019 21:42:05 +0200 Message-Id: <20190625194215.14927-1-krzesimir@kinvolk.io> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org These patches try to test the fix made in commit e2f7fc0ac695 ("bpf: fix undefined behavior in narrow load handling"). The problem existed in the generated BPF bytecode that was doing a 32bit narrow read of a 64bit field, so to test it the code would need to be executed. Currently the only such field exists in BPF_PROG_TYPE_PERF_EVENT, which was not supported by bpf_prog_test_run(). I'm sending these patches to bpf-next now as they introduce a new feature. But maybe some of those patches could go to the bpf branch? There is a bit of yak shaving to do for the test to be run: 1. Print why the program could not be run (patch 1). 2. Some fixes for errno clobbering (patches 2 and 3). 3. Using bpf_prog_test_run_xattr, so I can pass ctx_in stuff too (patch 4). 4. Adding ctx stuff to struct bpf_test (patch 5). 5. Some tools headers syncing (patches 6 and 7). 6. Implement bpf_prog_test_run for perf event programs and test it (patches 8 and 9). The last point is where I'm least sure how things should be done properly: 1. There is a bunch of stuff to prepare for the bpf_perf_prog_read_value to work, and that stuff is very hacky. I would welcome some hints about how to set up the perf_event and perf_sample_data structs in a way that is a bit more future-proof than just setting some fields in a specific way, so some other code won't use some other fields (like setting event.oncpu to -1 to avoid event.pmu to be used for reading the value of the event). 2. The tests try to see if the test run for perf event sets up the context properly, so they verify the struct pt_regs contents. They way it is currently written Works For Me, but surely it won't work on other arch. So what would be the way forward? Just put the test case inside #ifdef __x86_64__? 3. Another thing in tests - I'm trying to make sure that the bpf_perf_prog_read_value helper works as it seems to be the only bpf perf helper that takes the ctx as a parameter. Is that enough or I should test other helpers too? About the test itself - I'm not sure if it will work on a big endian machine. I think it should, but I don't have anything handy here to verify it. Krzesimir Nowak (10): selftests/bpf: Print a message when tester could not run a program selftests/bpf: Avoid a clobbering of errno selftests/bpf: Avoid another case of errno clobbering selftests/bpf: Use bpf_prog_test_run_xattr selftests/bpf: Allow passing more information to BPF prog test run tools headers: Adopt compiletime_assert from kernel sources tools headers: sync struct bpf_perf_event_data bpf: Implement bpf_prog_test_run for perf event programs selftests/bpf: Add tests for bpf_prog_test_run for perf events progs selftests/bpf: Test correctness of narrow 32bit read on 64bit field kernel/trace/bpf_trace.c | 107 +++++++++++ tools/include/linux/compiler.h | 28 +++ tools/include/uapi/linux/bpf_perf_event.h | 1 + tools/testing/selftests/bpf/test_verifier.c | 172 ++++++++++++++++-- .../selftests/bpf/verifier/perf_event_run.c | 93 ++++++++++ .../bpf/verifier/perf_event_sample_period.c | 8 + .../testing/selftests/bpf/verifier/var_off.c | 20 ++ 7 files changed, 414 insertions(+), 15 deletions(-) create mode 100644 tools/testing/selftests/bpf/verifier/perf_event_run.c -- 2.20.1