From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752192AbbLCR75 (ORCPT ); Thu, 3 Dec 2015 12:59:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46933 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751660AbbLCR74 (ORCPT ); Thu, 3 Dec 2015 12:59:56 -0500 Date: Thu, 3 Dec 2015 11:59:53 -0600 From: Josh Poimboeuf To: Chris J Arges Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, jikos@kernel.org, pmladek@suse.com, mbenes@suse.cz, jeyu@redhat.com Subject: Re: [PATCH 0/3 v9] livepatch: disambiguate symbols with the same name Message-ID: <20151203175953.GE11394@treble.redhat.com> References: <1448040325-32498-1-git-send-email-chris.j.arges@canonical.com> <1449024076-16034-1-git-send-email-chris.j.arges@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1449024076-16034-1-git-send-email-chris.j.arges@canonical.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 01, 2015 at 08:40:53PM -0600, Chris J Arges wrote: > Currently, patching objects with duplicate symbol names fail because the > creation of the sysfs function directory collides with the previous > attempt. Appending old_addr to the function name is problematic as it > reveals the address of the function being patch to a normal user. Using > the symbol's occurrence in kallsyms to postfix the function name in the > sysfs directory solves the issue of having consistent unique names and > ensuring that the address is not exposed to a normal user. > > In addition, using the symbol position as the user's method to disambiguate > symbols instead of addr allows for disambiguating symbols in modules as > well for both function addresses and for relocs. This also simplifies much > of the code. Special handling for kASLR is no longer needed and can be > removed. The klp_find_verify_func_addr function can be replaced by > klp_find_object_symbol, and klp_verify_vmlinux_symbol and its callback can > be removed completely. > > The following set of patches use symbol positioning instead of old > addresses to disambiguate symbols that have the same name in a given > object. This is necessary in order to be able to patch symbols with the > same name within the same object. This requires modifications to the > klp_func and klp_reloc structures to add an additional element. In addition > the scheme used for the func directory in sysfs is modified to append the > symbols occurrence in kallsyms. > > In addition, I've tested this patchset against a modified kpatch. I > modified the kpatch livepatch scaffolding to set lreloc->sympos = 0, and > lfunc->old_sympos to the nth occurrence of the symbol for that object in > kallsyms. I was able to patch the same test patch as described here: > https://github.com/dynup/kpatch/issues/493 > I've also tested this with sample livepatch code to test if the various > old_sympos values work for unique and duplicate functions. > > v9: > - use mod->name instead of mod->obj->name for klp_find_object_symbol in > klp_write_object_relocations > - rebase on current master > - tested with kpatch For the series: Acked-by: Josh Poimboeuf -- Josh