From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from devianza.investici.org (devianza.investici.org [198.167.222.108]) (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 11C1C233954; Tue, 18 Aug 2026 23:12:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.167.222.108 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787094764; cv=none; b=CT+YLwdb2Ww06/Fc42OK98qrgLM/nHy3MqurjOu5SVvrbI0GOC0TTEEC8OCRpDqqHln+rNxJVVktWlwQkUzzXhnhGYVfEZbr5frYT5j9r9hiSyo62J83SBVW6LZ+ao04OU+YnXWxCJJv/R5N7hpNXLZbDx9t0B6bx5saZptxikA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787094764; c=relaxed/simple; bh=KnmdjJGlDiEcqiwyb2gL1oqhiezN0ptxk/Vng4N7kXw=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=akT2ayqTryTjKeeEyuGDXp7oAyW75DkBfISBo48XF9o2SSeDHV14A8SGuQAWF9OAkshaLoy3/xo8jSAYVetIeLb0lTQwzhtSOMyJDpQXd+9Xm7UOH8UHHm3XiZZq2fcyo15HJlic0BnyZRJjfdHFeowd2iJvGqUNui44xG/tuUo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=grrlz.net; spf=pass smtp.mailfrom=grrlz.net; dkim=pass (1024-bit key) header.d=grrlz.net header.i=@grrlz.net header.b=jTqupWrr; arc=none smtp.client-ip=198.167.222.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=grrlz.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=grrlz.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=grrlz.net header.i=@grrlz.net header.b="jTqupWrr" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=grrlz.net; s=stigmate; t=1787094760; bh=i5yTHM9sTvE7JYLqlpPURxrPO43udIfu90NwaYLGjvU=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=jTqupWrrAewzxi+451xcuZJ4gYi50NGghK7MXFtUJeBfww2AgSDqNNBZ5CBQUrQFg r1ULlR6GzX2jBaUKGgdTsnH348GY6he5ECTLQ33QEYO7OiAMIL4JAsGpFA2EWfdWVY HeByGcKrDpyN+HZlCsM8xPGA4Xc8oFVS969dhnxs= Received: from mx2.investici.org (unknown [127.0.0.1]) by devianza.investici.org (Postfix) with ESMTP id 4hPlpw0M1Nz6vYy; Tue, 18 Aug 2026 23:12:40 +0000 (UTC) Received: by mx2.investici.org (Postfix) id 4hPlpv3r3vz4y6W; Tue, 18 Aug 2026 23:12:39 +0000 (UTC) Date: Wed, 19 Aug 2026 00:12:40 +0100 From: Bradley Morgan To: Masami Hiramatsu CC: Naveen N Rao , "David S . Miller" , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: =?US-ASCII?Q?Re=3A_=5BPATCH_v2=5D_kprobes=3A_use_DEFINE=5FD?= =?US-ASCII?Q?EBUGFS=5FATTRIBUTE_for_the_enabled_knob?= In-Reply-To: <20260819080813.d66950e37e660e018dfb19e9@kernel.org> References: <20260818015318.24103-1-include@grrlz.net> <20260819080813.d66950e37e660e018dfb19e9@kernel.org> Message-ID: <9533DBAB-DED1-4D61-93ED-AEFA2C585454@grrlz.net> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit On 19 August 2026 00:08:13 BST, Masami Hiramatsu wrote: >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. > ehhhhh, well, my description very well tells someone about why this is bad, and a hack, and everything. Your description is good though... But I love to have my personality in my descriptions :( >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 >> > > > Thanks!