From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 F246731327A; Tue, 18 Aug 2026 23:08:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787094499; cv=none; b=R/diqqy5rFLWzHXsLbgZX4fw1+7nJ1C+H0fjwVNICOL14175VZRvOjqeUx/rKi7bzC40qE1PyOWsF/7HfPkFAkGcQH3uNJE5ziu2+9VUjy/V5aFWqNPKqIONfDobDgE3Ij0TG168ANL+IwxwAfkAMickP9IWGwCpEZZAziQQloA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787094499; c=relaxed/simple; bh=I0o7jgGqUArAoL8PV8DAwsVh/ZbPd6qFZDJ2H5HtaU0=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=bCH2Sfbe2XTPBKh6pAwuWqk28JXQR6ZPyvsrvRc3ns51dl5lsW3WPYAiQl9YAjjabDrV+QABMlqSiDt9zlVJR2GVNSOmlYLF0N1DweeAQu1fJ+GKQdxHNenM+AqheOjmafxH9nacN4gmI9iDjUIaPnxLqoRNDnHs7Z2KdHsKldw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=B+wCZoz6; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="B+wCZoz6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 467C11F000E9; Tue, 18 Aug 2026 23:08:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787094497; bh=VfKx5DNr0pE+W+fY6zLxse/TAnLY9w43ytpE/LA6q9M=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=B+wCZoz6pt4hWNcT1/YJtawUyXBFIl9X3myOoYFzbM05XJPy+AFNxHxWc9M8x9hXg uFfYQdMkUlK0qBvfne17GI+sbGARm5hmCrlSAmvEnFoZcV8Zad3alQ/0C9HW/atOmS gvPBjKW08PV/e4zP7p8uIRlhQyU3gRgL1PNbfgheUx6nyZfGa8AjaB6mcBoloK9tWO Cj3qkNrhrKm5TtfTQdPjeaoMn614uQCoEjdnndVXocNlijIpz+/dtWZlw2ya7CFf66 WU9Ndc4BuoOvtELrI5dVsXEpcsRD1rflu2FdOOvcf6Glb4IEGjKhZN1uN6+M/FbsxY XRpfgpjc/xuug== Date: Wed, 19 Aug 2026 08:08:13 +0900 From: Masami Hiramatsu (Google) To: Bradley Morgan Cc: Naveen N Rao , "David S . Miller" , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH v2] kprobes: use DEFINE_DEBUGFS_ATTRIBUTE for the enabled knob Message-Id: <20260819080813.d66950e37e660e018dfb19e9@kernel.org> In-Reply-To: <20260818015318.24103-1-include@grrlz.net> References: <20260818015318.24103-1-include@grrlz.net> 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 On Tue, 18 Aug 2026 01:53:18 +0000 Bradley Morgan wrote: > This enabled knob is a disgusting terrible hack. It has rolled its > own read/write pair since 2007, writing '1' or '0' into a three byte > buffer by hand just to print a single character, with an XXX comment > begging debugfs for write callbacks on bool files. > DEFINE_DEBUGFS_ATTRIBUTE showed up in 2016 and does exactly that, so > the disgusting terrible hack has outlived its excuse for nine years. > Kill it, and the stale comment with it. In other words, does this mean something like the following? This "enable" knob implemented custom read/write logic, manually writing "1" or "0" to a 3-byte buffer solely to output a single character. As suggested by comments calling for `debugfs` to support write callbacks for boolean files, using `DEFINE_DEBUGFS_ATTRIBUTE` eliminates the need for these callbacks. Thanks, > > The behavior does not change, except the write only accepts 0/1 now > instead of y/n/on/off, and nothing uses anything else. > > Signed-off-by: Bradley Morgan > --- > Changes since v1: > - Added the missing Signed-off-by, sorry. > > kernel/kprobes.c | 43 +++++++++---------------------------------- > 1 file changed, 9 insertions(+), 34 deletions(-) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index bfc89083daa9..044c6b5fd2aa 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -3013,47 +3013,22 @@ static int disarm_all_kprobes(void) > return ret; > } > > -/* > - * XXX: The debugfs bool file interface doesn't allow for callbacks > - * when the bool state is switched. We can reuse that facility when > - * available > - */ > -static ssize_t read_enabled_file_bool(struct file *file, > - char __user *user_buf, size_t count, loff_t *ppos) > +static int kprobes_enabled_set(void *data, u64 val) > { > - char buf[3]; > + if (val) > + return arm_all_kprobes(); > > - if (!kprobes_all_disarmed) > - buf[0] = '1'; > - else > - buf[0] = '0'; > - buf[1] = '\n'; > - buf[2] = 0x00; > - return simple_read_from_buffer(user_buf, count, ppos, buf, 2); > + return disarm_all_kprobes(); > } > > -static ssize_t write_enabled_file_bool(struct file *file, > - const char __user *user_buf, size_t count, loff_t *ppos) > +static int kprobes_enabled_get(void *data, u64 *val) > { > - bool enable; > - int ret; > - > - ret = kstrtobool_from_user(user_buf, count, &enable); > - if (ret) > - return ret; > - > - ret = enable ? arm_all_kprobes() : disarm_all_kprobes(); > - if (ret) > - return ret; > - > - return count; > + *val = !kprobes_all_disarmed; > + return 0; > } > > -static const struct file_operations fops_kp = { > - .read = read_enabled_file_bool, > - .write = write_enabled_file_bool, > - .llseek = default_llseek, > -}; > +DEFINE_DEBUGFS_ATTRIBUTE(fops_kp, kprobes_enabled_get, > + kprobes_enabled_set, "%llu\n"); > > static int __init debugfs_kprobe_init(void) > { > -- > 2.47.3 > -- Masami Hiramatsu (Google)