From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) (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 0BB52212B07; Tue, 18 Mar 2025 18:06:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.60.130.6 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742321227; cv=none; b=iYTitGZ+ICqTcbh38BM2r1cyXLK08wU/y0cNXMby34rYAEajgKXjiF4FPaIZ2nNZ2bJw1qVgBfhwv5Ap0vElmibgPm3GQpntsuGJJvUeGtumDP/m93KtX+zLcpfxQgMVz6cAUIUOsF2Qbb/JO6oa6YKQ25azc1lDmYJjnBo6ezw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742321227; c=relaxed/simple; bh=ObvK4V5+WTs9GjlkzhLf22kOTTKhjSK/UvNK71fc+iI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=avuzkEjro65qZSENMPFIXhXmm1KWMlREGug9aBqD2gtfuOvF3Sp53YeBwgMvMCMzQW6md4TJzqsKmI8KEaweCCH92ELIyD0jy7O7JLuNTjJjXo0XNNyGUth5Z/6jmYxwYZ3Chd2EqSHvN2CenYdiaAuXiV0Wd0/RclVy6YQBS+s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com; spf=pass smtp.mailfrom=igalia.com; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b=DBzlswaw; arc=none smtp.client-ip=178.60.130.6 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=igalia.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=igalia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="DBzlswaw" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:In-Reply-To:From: References:Cc:To:Subject:MIME-Version:Date:Message-ID:Sender:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=xi5z/098n3s55drfJnQC0KGieJT8vR+QHgsSyHMCSwc=; b=DBzlswawCpcdwZoCIaLOvmz4bR f0qEhXAdTinfikQUSQKatFmc4DOOS06n8K1sJFrOSNcUeLsXDHdJtNOOqIoE8tMVCawIxhjr7V0il wj7gIb8Wa/bOAL4CwOk29espYzdobGhMYvbkCHF6VHxQtcfoa7ax0Pyk3HAHtUSu/fg/xTpJm1xTt IiNOB4hK2IvroqdJaIkKfy3UKumgrzzhUswjeq0+prccirjOKyNlc3/hOJZX8zgnN5eKsjqjMl02e ARHGKMUHhTSXc/fvmwe4vsdSRTzB13/2bXVwzUV6PAVlRDiOf2K221sWXTZQAwmOS33ro4q6Qysbs /dIdWobg==; Received: from [223.233.76.123] (helo=[192.168.1.12]) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_128_GCM:128) (Exim) id 1tubKz-002s83-Kp; Tue, 18 Mar 2025 19:06:49 +0100 Message-ID: <24766119-3aa2-fe88-878a-90a2794cca8f@igalia.com> Date: Tue, 18 Mar 2025 23:36:40 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH RFC 0/2] Dynamically allocate memory to store task's full name Content-Language: en-US To: Kees Cook Cc: Andres Rodriguez , Bhupesh , akpm@linux-foundation.org, kernel-dev@igalia.com, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, oliver.sang@intel.com, lkp@intel.com, laoar.shao@gmail.com, pmladek@suse.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, alexei.starovoitov@gmail.com, andrii.nakryiko@gmail.com, mirq-linux@rere.qmqm.pl, peterz@infradead.org, willy@infradead.org, david@redhat.com, viro@zeniv.linux.org.uk, ebiederm@xmission.com, brauner@kernel.org, jack@suse.cz, mingo@redhat.com, juri.lelli@redhat.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com References: <20250314052715.610377-1-bhupesh@igalia.com> <202503141420.37D605B2@keescook> <8b11d5f6-bb16-7af6-8377-bb0951fcfb60@igalia.com> <202503180846.EAB79290D@keescook> From: Bhupesh Sharma In-Reply-To: <202503180846.EAB79290D@keescook> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Kees, On 3/18/25 9:21 PM, Kees Cook wrote: > On Tue, Mar 18, 2025 at 04:49:28PM +0530, Bhupesh Sharma wrote: >> On 3/15/25 1:13 PM, Andres Rodriguez wrote: >>> On 3/14/25 14:25, Kees Cook wrote: >>>> On Fri, Mar 14, 2025 at 10:57:13AM +0530, Bhupesh wrote: >>>>> While working with user-space debugging tools which work especially >>>>> on linux gaming platforms, I found that the task name is truncated due >>>>> to the limitation of TASK_COMM_LEN. >>>>> >>>>> For example, currently running 'ps', the task->comm value of a long >>>>> task name is truncated due to the limitation of TASK_COMM_LEN. >>>>>      create_very_lon >>>>> >>>>> This leads to the names passed from userland via pthread_setname_np() >>>>> being truncated. >>>> So there have been long discussions about "comm", and it mainly boils >>>> down to "leave it alone". For the /proc-scraping tools like "ps" and >>>> "top", they check both "comm" and "cmdline", depending on mode. The more >>>> useful (and already untruncated) stuff is in "cmdline", so I suspect it >>>> may make more sense to have pthread_setname_np() interact with that >>>> instead. Also TASK_COMM_LEN is basically considered userspace ABI at >>>> this point and we can't sanely change its length without breaking the >>>> world. >>>> >>> Completely agree that comm is best left untouched. TASK_COMM_LEN is >>> embedded into the kernel and the pthread ABI changes here should be >>> avoided. >>> >> So, basically my approach _does not_ touch TASK_COMM_LEN at all. The normal >> 'TASK_COMM_LEN' 16byte design remains untouched. >> Which means that all the legacy / existing ABi which uses 'task->comm' and >> hence are designed / written to handle 'TASK_COMM_LEN' 16-byte name, >> continue to work as before using '/proc/$pid/task/$tid/comm'. >> >> This change-set only adds a _parallel_ dynamically allocated >> 'task->full_name' which can be used by interested users via >> '/proc/$pid/task/$tid/full_name'. > I don't want to add this to all processes at exec time as the existing > solution works for those processes: read /proc/$pid/cmdline. > > That said, adding another pointer to task_struct isn't to bad I guess, > and it could be updated by later calls. Maybe by default it just points > to "comm". Sure. > >> I am fine with adding either '/proc/$pid/task/$tid/full_name' or >> '/proc/$pid/task/$tid/debug_name' (actually both of these achieve the same). >> The new / modified users (especially the debug applications you listed >> above) can switch easily to using '/proc/$pid/task/$tid/full_name' instead >> of ''/proc/$pid/task/$tid/comm' >> >> AFAIK we already achieved for the kthreads using d6986ce24fc00 ("kthread: >> dynamically allocate memory to store kthread's full name"), which adds >> 'full_name' in parallel to 'comm' for kthread names. > If we do this for task_struct, we should remove "full_name" from kthread > and generalize it for all processes. > Got it. Ok, let me rework the series so that we have a unified 'full_name' inside 'task_struct' and have kthread use it as well. I will send a v2 accordingly. Thanks, Bhupesh