From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932178AbeAIXMp convert rfc822-to-8bit (ORCPT + 1 other); Tue, 9 Jan 2018 18:12:45 -0500 Received: from mail.kernel.org ([198.145.29.99]:43514 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932091AbeAIXMn (ORCPT ); Tue, 9 Jan 2018 18:12:43 -0500 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0D41D2064D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Tue, 9 Jan 2018 18:12:41 -0500 From: Steven Rostedt To: changbin.du@intel.com Cc: jolsa@redhat.com, peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: Re: [PATCH 3/3] tracing: don't set parser->cont if it has reached the end of input buffer Message-ID: <20180109181241.6b3f5ffb@vmware.local.home> In-Reply-To: <1515491748-25926-4-git-send-email-changbin.du@intel.com> References: <1515491748-25926-1-git-send-email-changbin.du@intel.com> <1515491748-25926-4-git-send-email-changbin.du@intel.com> X-Mailer: Claws Mail 3.15.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: On Tue, 9 Jan 2018 17:55:48 +0800 changbin.du@intel.com wrote: > From: Changbin Du > > We should not set parser->cont if it has reached the end of input buffer. > And since some callers (like ftrace_graph_write()) treat it as an error > condition if trace_parser_cont() returns true. This will break existing use cases. In fact you are removing the entire point of this code. It NEEDS to continue if it reached the end of the input buffer. I do things like: # cat file > set_ftrace_filter where the file has a list of function names. It writes in blocks, and it could very well have a function name split between two writes where the write is at the end of the buffer but not finished writing the function name. > > For example, if userspace set 'set_ftrace_filter' by writing: > write(3, "abcdefg", 7) >>From my point of view, the above isn't done writing the function name yet and we SHOULD continue waiting for more input. BIG NACK on this patch. Sorry. I'm guessing you have some program that writes only the strlen() of these strings. That's wrong, you need to write "strlen()+1". Write some real white space between calls, it will work. Add a "write(fd, " ", 1)" between calls if you need to. Please don't change the kernel to fix some bad use case. Especially when your fix will break existing use cases. -- Steve > > Then in the kernel function ftrace_regex_write(), ftrace_process_regex() > will not be executed. The result is that the given filter will not be > applied at all. > > ftrace_regex_write() { > ... > read = trace_get_user(parser, ubuf, cnt, ppos); > if (read >= 0 && trace_parser_loaded(parser) && > !trace_parser_cont(parser)) { > ret = ftrace_process_regex(iter, parser->buffer, > parser->idx, enable); > ... > } > ... > } > > Signed-off-by: Changbin Du