From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB1C32FD7BC; Tue, 14 Oct 2025 14:52:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760453527; cv=none; b=XTqVcm2DXoJQQIlIbQSYdB4CPEnr0hbs3V+OOb1Wk10Oew1S9VpuwyOjaN2eKHgFg2RSkq/J0cnPv1tKp+dCh2StchD+sbPY9ZoZZ4EIhFzWpPtHYtxG6VX785FW4CMj+L0B5pQiCr5fZg0sOjo6oirkcKdNqRhVz2bRtcpXc64= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760453527; c=relaxed/simple; bh=dXxH4+BCkV70G2cUOYaRDyMCMT92iXGER7n8AbGM3As=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=IigVHpJJzYpgqejpxGv2rDO0MFEb87QiHYnWIzhZ8NOB50RORjDgG2XkyKZeliTCMRUeDITidjHupWij46HDubPe7/hO/nrhxKJ9qlSWlLtf4gDiY2/tjXZMZCJ8/8tKi6tpjorWhyiI7px1A/KU/uVa5CCkzZ1TPrDHvB/EM2U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MgtFYdsI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MgtFYdsI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B697C4CEE7; Tue, 14 Oct 2025 14:52:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1760453523; bh=dXxH4+BCkV70G2cUOYaRDyMCMT92iXGER7n8AbGM3As=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=MgtFYdsIZvkvkL3H4Aj00ppBACazuQ6mbX3kIhfPCZopy2f7MNDY17TYjpeNZ4r/H 1aM3OKvqVs5CvZyHZb/2+8is5TjPF2h4jn8EdMTDD2RknG+WNk1Eo4W8puzvMVW2xs CLl/KK8sjl3xdULn/kEAFBfHcUPtPUGpg9cCKVPHiFpo+Hccr4NZRa+xW/HMYCN6sM 7yvYHcwv9aObZ4o2KTIf+iYSQzF1WgUGgLNLbr/e7LCQ0Yqt14xgwWgajdaKWvj+gD x7i0Jw6kbZbiWKPDgEI0eRxhU/51sgsSMPuFbC1xxeXA+DrZt+dM1B+8KtHZRfmud/ X57pLQJNm+QoA== Date: Tue, 14 Oct 2025 23:51:59 +0900 From: Masami Hiramatsu (Google) To: Menglong Dong Cc: rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiang.biao@linux.dev, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org Subject: Re: [PATCH v2 1/2] tracing: fprobe: optimization for entry only case Message-Id: <20251014235159.fdfc2444582ea15de822c0b4@kernel.org> In-Reply-To: <20251010033847.31008-2-dongml2@chinatelecom.cn> References: <20251010033847.31008-1-dongml2@chinatelecom.cn> <20251010033847.31008-2-dongml2@chinatelecom.cn> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Hi Menglong, I remember why I haven't implement this. On Fri, 10 Oct 2025 11:38:46 +0800 Menglong Dong wrote: > + > +static struct ftrace_ops fprobe_ftrace_ops = { > + .func = fprobe_ftrace_entry, > + .flags = FTRACE_OPS_FL_SAVE_REGS, Actually, this flag is the problem. This can fail fprobe on architecture which does not support CONFIG_DYNAMIC_FTRACE_WITH_REGS (e.g. arm64, riscv) * SAVE_REGS - The ftrace_ops wants regs saved at each function called * and passed to the callback. If this flag is set, but the * architecture does not support passing regs * (CONFIG_DYNAMIC_FTRACE_WITH_REGS is not defined), then the * ftrace_ops will fail to register, unless the next flag * is set. fgraph has a special entry code for saving ftrace_regs. So at least we need to fail back to fgraph if arch does not support CONFIG_DYNAMIC_FTRACE_WITH_REGS. Thank you, -- Masami Hiramatsu (Google)