From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Tue, 07 Aug 2018 13:36:37 +0200 (CEST) Received: from mx3-rdu2.redhat.com ([66.187.233.73]:43808 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by eddie.linux-mips.org with ESMTP id S23994680AbeHGLgeS7rPB (ORCPT ); Tue, 7 Aug 2018 13:36:34 +0200 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B59F540241C4; Tue, 7 Aug 2018 11:36:27 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id B15801C663; Tue, 7 Aug 2018 11:36:23 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 7 Aug 2018 13:36:27 +0200 (CEST) Date: Tue, 7 Aug 2018 13:36:23 +0200 From: Oleg Nesterov To: Ravi Bangoria Cc: srikar@linux.vnet.ibm.com, rostedt@goodmis.org, mhiramat@kernel.org, liu.song.a23@gmail.com, peterz@infradead.org, mingo@redhat.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@redhat.com, namhyung@kernel.org, linux-kernel@vger.kernel.org, ananth@linux.vnet.ibm.com, alexis.berlemont@gmail.com, naveen.n.rao@linux.vnet.ibm.com, linux-arm-kernel@lists.infradead.org, linux-mips@linux-mips.org, linux@armlinux.org.uk, ralf@linux-mips.org, paul.burton@mips.com Subject: Re: [PATCH v7 3/6] Uprobes: Support SDT markers having reference count (semaphore) Message-ID: <20180807113622.GC19831@redhat.com> References: <20180731035143.11942-1-ravi.bangoria@linux.ibm.com> <20180731035143.11942-4-ravi.bangoria@linux.ibm.com> <20180803112455.GA13794@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 07 Aug 2018 11:36:27 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 07 Aug 2018 11:36:27 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'oleg@redhat.com' RCPT:'' Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 65446 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: oleg@redhat.com Precedence: bulk List-help: List-unsubscribe: List-software: Ecartis version 1.0.0 List-Id: linux-mips X-List-ID: linux-mips List-subscribe: List-owner: List-post: List-archive: X-list: linux-mips Hi Ravi, On 08/06, Ravi Bangoria wrote: > > >> +static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm) > >> +{ > >> + struct delayed_uprobe *du; > >> + > >> + if (delayed_uprobe_check(uprobe, mm)) > >> + return 0; > >> + > >> + du = kzalloc(sizeof(*du), GFP_KERNEL); > >> + if (!du) > >> + return -ENOMEM; > >> + > >> + du->uprobe = uprobe; > >> + du->mm = mm; > > > > I am surprised I didn't notice this before... > > > > So > > du->mm = mm; > > > > is fine, mm can't go away, uprobe_clear_state() does delayed_uprobe_remove(NULL,mm). > > > > But > > du->uprobe = uprobe; > > > > doesn't look right, uprobe can go away and it can be freed, its memory can be reused. > > We can't rely on remove_breakpoint(), > > > I'm sorry. I didn't get this. How can uprobe go away without calling > uprobe_unregister() > -> rergister_for_each_vma() > -> remove_breakpoint() > And remove_breakpoint() will get called assuming that _unregister() will find the same vma with the probed insn. But as I said, the application can munmap the probed page/vma. No? > > Also. delayed_uprobe_add() should check the list and avoid duplicates. Otherwise the > > trivial > > > > for (;;) > > munmap(mmap(uprobed_file)); > > > > will eat the memory until uprobe is unregistered. > > > I'm already calling delayed_uprobe_check(uprobe, mm) from delayed_uprobe_add(). Oops ;) Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 From: oleg@redhat.com (Oleg Nesterov) Date: Tue, 7 Aug 2018 13:36:23 +0200 Subject: [PATCH v7 3/6] Uprobes: Support SDT markers having reference count (semaphore) In-Reply-To: References: <20180731035143.11942-1-ravi.bangoria@linux.ibm.com> <20180731035143.11942-4-ravi.bangoria@linux.ibm.com> <20180803112455.GA13794@redhat.com> Message-ID: <20180807113622.GC19831@redhat.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Ravi, On 08/06, Ravi Bangoria wrote: > > >> +static int delayed_uprobe_add(struct uprobe *uprobe, struct mm_struct *mm) > >> +{ > >> + struct delayed_uprobe *du; > >> + > >> + if (delayed_uprobe_check(uprobe, mm)) > >> + return 0; > >> + > >> + du = kzalloc(sizeof(*du), GFP_KERNEL); > >> + if (!du) > >> + return -ENOMEM; > >> + > >> + du->uprobe = uprobe; > >> + du->mm = mm; > > > > I am surprised I didn't notice this before... > > > > So > > du->mm = mm; > > > > is fine, mm can't go away, uprobe_clear_state() does delayed_uprobe_remove(NULL,mm). > > > > But > > du->uprobe = uprobe; > > > > doesn't look right, uprobe can go away and it can be freed, its memory can be reused. > > We can't rely on remove_breakpoint(), > > > I'm sorry. I didn't get this. How can uprobe go away without calling > uprobe_unregister() > -> rergister_for_each_vma() > -> remove_breakpoint() > And remove_breakpoint() will get called assuming that _unregister() will find the same vma with the probed insn. But as I said, the application can munmap the probed page/vma. No? > > Also. delayed_uprobe_add() should check the list and avoid duplicates. Otherwise the > > trivial > > > > for (;;) > > munmap(mmap(uprobed_file)); > > > > will eat the memory until uprobe is unregistered. > > > I'm already calling delayed_uprobe_check(uprobe, mm) from delayed_uprobe_add(). Oops ;) Oleg.