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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-483a3dfd902sm39760875e9.7.2026.02.21.04.00.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 21 Feb 2026 04:00:36 -0800 (PST) Date: Sat, 21 Feb 2026 12:00:35 +0000 From: David Laight To: bot+bpf-ci@kernel.org Cc: jolsa@kernel.org, andrii@kernel.org, bpf@vger.kernel.org, linux-kernel@vger.kernel.org, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org, eddyz87@gmail.com, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCHv4 bpf-next 2/5] libbpf: Add support to detect nop,nop5 instructions combo for usdt probe Message-ID: <20260221120035.4562df85@pumpkin> In-Reply-To: References: <20260220104220.634154-3-jolsa@kernel.org> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 20 Feb 2026 11:24:45 +0000 (UTC) bot+bpf-ci@kernel.org wrote: > > diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c > > index d1524f6f54ae..c81e0a58caf5 100644 > > --- a/tools/lib/bpf/usdt.c > > +++ b/tools/lib/bpf/usdt.c > > [ ... ] > > > +#if defined(__x86_64__) > > +static bool has_nop_combo(int fd, long off) > > +{ > > + static unsigned char nop_combo[6] = { > ^^^^^^^^^^^^^^^^^^^^^^ > > Should nop_combo be declared const? It is a read-only lookup table > used only in the memcmp() below. Actually you either want 'static const unsigned char' or just 'unsigned char'. In either case gcc optimises away the array, the call to memcmp(), and just compares with 32bit and 64bit constants. > > > + 0x90, 0x0f, 0x1f, 0x44, 0x00, 0x00 /* nop,nop5 */ > > + }; > > + unsigned char buf[6] = {}; No need to initialise buf[]; David > > + > > + if (pread(fd, buf, 6, off) != 6) > > + return false; > > + return memcmp(buf, nop_combo, 6) == 0; > > +} > > [ ... ] > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/22221513473 > > AI-authorship-score: low > AI-authorship-explanation: Domain-specific optimization from established BPF/tracing maintainer with iterative lore review history and deep x86_64 uprobe internals knowledge. > issues-found: 1 > issue-severity-score: low > issue-severity-explanation: Missing const qualifier on a static read-only byte array is a minor C best practice deviation with no runtime impact.