Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753977Ab3JDKal (ORCPT ); Fri, 4 Oct 2013 06:30:41 -0400 Received: from e23smtp03.au.ibm.com ([202.81.31.145]:47354 "EHLO e23smtp03.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753710Ab3JDKaj (ORCPT ); Fri, 4 Oct 2013 06:30:39 -0400 Subject: [RFC] [PATCH 00/19] Non disruptive application core dump infrastructure using task_work_add() To: linux-kernel@vger.kernel.org From: Janani Venkataraman Cc: amwang@redhat.com, rdunlap@xenotime.net, andi@firstfloor.org, aravinda@linux.vnet.ibm.com, hch@lst.de, mhiramat@redhat.com, jeremy.fitzhardinge@citrix.com, xemul@parallels.com, suzuki@linux.vnet.ibm.com, kosaki.motohiro@jp.fujitsu.com, adobriyan@gmail.com, tarundsk@linux.vnet.ibm.com, vapier@gentoo.org, roland@hack.frob.com, tj@kernel.org, ananth@linux.vnet.ibm.com, gorcunov@openvz.org, avagin@openvz.org, oleg@redhat.com, eparis@redhat.com, d.hatayama@jp.fujitsu.com, james.hogan@imgtec.com, akpm@linux-foundation.org, torvalds@linux-foundation.org Date: Fri, 04 Oct 2013 16:00:12 +0530 Message-ID: <20131004102532.1612.24185.stgit@f19-x64> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100410-6102-0000-0000-00000447AA60 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4873 Lines: 125 Hi all, The following series implements an infrastructure for capturing the core of an application without disrupting its process. So ideally what we are trying to do is to export the infrastructure using /proc/pid/core. Reading the file would give an ELF Format core-dump at that instant non-disruptively, without sending signals. This would involve basically three operations: 1) Holding the threads of a process without sending a signal (SIGSTOP). At this point we can collect the register set snapshot and collect other information required to create the ELF header. The above operation could be initiated with the open() call. 2) Once the ELF header is created, read() can return the CORE DUMP data including, the process memory page-by-page, based on the fpos (file position). 3) The threads could be released upon a close(). We discussed various approaches for the implemenation in the post given below. -https://lkml.org/lkml/2013/9/3/122 This series is based on the Task work add approach. We didn't adopt the CRIU approch because of the following reasons: * It is not upstream yet. * There are concerns about the security of the dump. * It involves a lot of changes and this approach provides a UNIX style interface. Task work add task_work_add() is an interface and an API. The task work add will run any queued work before returning to user space from the kernel. So that work is guaranteed to be done before user space can run again. So basically it queues a work for a task which is guaranteed to be executed when the task returns from kernel space to user space. * Exploit this function to hold the threads when they are returning to the user space. * Wait until all the threads of the process to be dumped, reach task_work_add. * Once all the threads have reached, the dump is taken and they are released. TODO: * A mechanism to know when all the threads have reached the task added. * A way to handle a case when one of the threads of the task to be dumped is blocked in the kernel. * We could also add the infrastructure under a config option, say:CONFIG_ELF_GENCORE * The current implementation doesn't wait for the threads to reach wait_for_completion(). Hence there is no guarantee of collecting the 'register set' reliably. We will address this issue in the next version. This is a prototype implementation to get reviews and comments. Patches 1 to 8 deals with re-arranging the ELF code to be reusable by the infrastructure. Patches 9 to 19 implements the infrastructure. Please let me know your reviews and comments. Janani Venkataraman (19): Create elfcore-common.c for ELF class independent core generation helpers Make vma_dump_size() generic Make fill_psinfo generic Rename compat versions of the reusable core generation routines Export the reusable ELF core generation routines Define API for reading arch specif Program Headers for Core ia64 impelementation for elf_core_copy_extra_phdrs() elf_core_copy_extra_phdrs() for UML Create /proc/pid/core entry Track the core generation requests Check if the process is an ELF executable Hold the threads using task_work_add Create ELF Header Create ELF Core notes Data Calculate the size of the core file Generate the data sections for ELF Core Identify the ELF class of the process Adding support for compat ELF class data structures Compat ELF class core generation support arch/ia64/kernel/elfcore.c | 34 +++ arch/x86/um/elfcore.c | 32 +++ fs/Makefile | 1 fs/binfmt_elf.c | 190 ++-------------- fs/compat_binfmt_elf.c | 7 + fs/elfcore-common.c | 169 ++++++++++++++ fs/proc/Makefile | 2 fs/proc/base.c | 2 fs/proc/gencore-compat-elf.c | 62 +++++ fs/proc/gencore-elf.c | 458 ++++++++++++++++++++++++++++++++++++++ fs/proc/gencore.c | 262 ++++++++++++++++++++++ fs/proc/gencore.h | 74 ++++++ fs/proc/internal.h | 1 include/linux/elfcore-internal.h | 72 ++++++ include/linux/elfcore.h | 3 kernel/elfcore.c | 6 16 files changed, 1209 insertions(+), 166 deletions(-) create mode 100644 fs/elfcore-common.c create mode 100644 fs/proc/gencore-compat-elf.c create mode 100644 fs/proc/gencore-elf.c create mode 100644 fs/proc/gencore.c create mode 100644 fs/proc/gencore.h create mode 100644 include/linux/elfcore-internal.h -- Janani -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/