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Sun, 25 Oct 2026 10:38:06 -0700 (PDT) Received: from localhost ([153.61.198.255]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3adebb1e37esm4046063a91.4.2026.10.25.10.38.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 25 Oct 2026 10:38:06 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Sun, 25 Oct 2026 17:38:05 +0000 Message-Id: Cc: , , "Menglong Dong" , "Steven Rostedt" Subject: Re: [PATCH bpf 1/2] x86/ftrace: Use jmp mode only where functions are aligned From: "Alexei Starovoitov" To: "Daniel Borkmann" , "Jiri Olsa" In-Reply-To: <8c2784c0-2b13-4cc2-b770-51bbb8006f26@iogearbox.net> References: <20261024073712.1074591-1-daniel@iogearbox.net> <8c2784c0-2b13-4cc2-b770-51bbb8006f26@iogearbox.net> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Sun, Oct 25, 2026 at 08:27 AM Daniel Borkmann wrote: > I had the below first as well, but then saw that there were similar issues > regarding function alignment in the past and they were solved on kconfig > level, some picks: > > - b3f11af9b2ce ("arm64: ftrace: forbid CALL_OPS with CC_OPTIMIZE_FOR_SIZE") > - a743f26d03a9 ("arm64: ftrace: Don't forbid CALL_OPS+CC_OPTIMIZE_FOR_SIZE with Clang") > - c41bf4326c7b ("riscv: ftrace: align patchable functions to 4 Byte boundary") > - 9315e22b0c0a ("arm64: ftrace: allow DIRECT_CALLS without CALL_OPS") I think those are different. They need the traced function to be aligned by design. CALL_OPS keeps an 8 byte literal in front of it. Here nothing needs C functions to be aligned. The callback is hit by the bit 0 check only because it goes through ftrace_call_replace(). > But I can also spin a v2 with the code change instead if preferred. I don't insist, but imo my approach is cleaner.