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(unknown []) by gzga-smtp-mtada-g0-0 (Coremail) with SMTP id _____wDnLGHROqdon1G_DQ--.32608S2; Thu, 21 Aug 2025 23:27:15 +0800 (CST) From: Jiawei Zhao To: ast@kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, yonghong.song@linux.dev, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH bpf-next v12 0/2] libbpf: fix USDT SIB argument handling causing unrecognized register error Date: Thu, 21 Aug 2025 15:27:10 +0000 Message-ID: <20250821152713.1024982-1-phoenix500526@163.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:_____wDnLGHROqdon1G_DQ--.32608S2 X-Coremail-Antispam: 1Uf129KBjvJXoWxWw4ktFy5Zr1xJr4UGF1UGFg_yoW5ArWfpF WrGws8trWDtas7GFsxXr42yw43WFs5GFWUJFn2qw1Yvr4rGFnrJrWxKw15JFnxGa97X34Y vF4qyFs8Gas5AaUanT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jopBfUUUUU= X-CM-SenderInfo: pskrv0dl0viiqvswqiywtou0bp/xtbBax2wiGinLsHhFwAAsY When using GCC on x86-64 to compile an usdt prog with -O1 or higher optimization, the compiler will generate SIB addressing mode for global array and PC-relative addressing mode for global variable, e.g. "1@-96(%rbp,%rax,8)" and "-1@4+t1(%rip)". The current USDT implementation in libbpf cannot parse these two formats, causing `bpf_program__attach_usdt()` to fail with -ENOENT (unrecognized register). This patch series adds support for SIB addressing mode in USDT probes. The main changes include: - add correct handling logic for SIB-addressed arguments in `parse_usdt_arg`. - add an usdt_o2 test case to cover SIB addressing mode. Testing shows that the SIB probe correctly generates 8@(%rcx,%rax,8) argument spec and passes all validation checks. The modification history of this patch series: Change since v1: - refactor the code to make it more readable - modify the commit message to explain why and how Change since v2: - fix the `scale` uninitialized error Change since v3: - force -O2 optimization for usdt.test.o to generate SIB addressing usdt and pass all test cases. Change since v4: - split the patch into two parts, one for the fix and the other for the test Change since v5: - Only enable optimization for x86 architecture to generate SIB addressing usdt argument spec. Change since v6: - Add an usdt_o2 test case to cover SIB addressing mode. - Reinstate the usdt.c test case. Change since v7: - Refactor modifications to __bpf_usdt_arg_spec to avoid increasing its size, achieving better compatibility - Fix some minor code style issues - Refactor the usdt_o2 test case, removing semaphore and adding GCC attribute to force -O2 optimization Change since v8: - Refactor the usdt_o2 test case, using assembly to force SIB addressing mode. Change since v9: - Only enable the usdt_o2 test case on x86_64 and i386 architectures since the SIB addressing mode is only supported on x86_64 and i386. Change since v10: - Replace `__attribute__((optimize("O2")))` with `#pragma GCC optimize("O1")` to fix the issue where the optimized compilation condition works improperly. - Renamed test case usdt_o2 and relevant files name to usdt_o1 in that O1 level optimization is enough to generate SIB addressing usdt argument spec. Change since v11: - Replace `STAP_PROBE1` with `STAP_PROBE_ASM` - Use bit fields instead of bit shifting operations - Merge the usdt_o1 test case into the usdt test case Jiawei Zhao (2): libbpf: fix USDT SIB argument handling causing unrecognized register error selftests/bpf: Enrich subtest_basic_usdt case in selftests to cover SIB handling logic tools/lib/bpf/usdt.bpf.h | 47 ++++++++++++++- tools/lib/bpf/usdt.c | 58 +++++++++++++++++-- tools/testing/selftests/bpf/prog_tests/usdt.c | 44 +++++++++++++- tools/testing/selftests/bpf/progs/test_usdt.c | 30 ++++++++++ 4 files changed, 170 insertions(+), 9 deletions(-) -- 2.43.0