Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932213AbaKSUfI (ORCPT ); Wed, 19 Nov 2014 15:35:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55570 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756132AbaKSUfG (ORCPT ); Wed, 19 Nov 2014 15:35:06 -0500 Date: Wed, 19 Nov 2014 14:34:30 -0600 From: Seth Jennings To: Miroslav Benes Cc: Josh Poimboeuf , Jiri Kosina , Vojtech Pavlik , Steven Rostedt , Petr Mladek , Christoph Hellwig , Greg KH , Andy Lutomirski , Masami Hiramatsu , live-patching@vger.kernel.org, x86@kernel.org, kpatch@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCHv2 2/3] kernel: add support for live patching Message-ID: <20141119203430.GA12517@cerebellum.variantweb.net> References: <1416187764-3341-1-git-send-email-sjenning@redhat.com> <1416187764-3341-3-git-send-email-sjenning@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 18, 2014 at 03:45:22PM +0100, Miroslav Benes wrote: > > On Sun, 16 Nov 2014, Seth Jennings wrote: > > [...] > > > diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h > > new file mode 100644 > > index 0000000..8b68fef > > --- /dev/null > > +++ b/include/linux/livepatch.h > > @@ -0,0 +1,68 @@ > > +/* > > + * livepatch.h - Live Kernel Patching Core > > + * > > + * Copyright (C) 2014 Seth Jennings > > + * > > + * This program is free software; you can redistribute it and/or > > + * modify it under the terms of the GNU General Public License > > + * as published by the Free Software Foundation; either version 2 > > + * of the License, or (at your option) any later version. > > + * > > + * This program is distributed in the hope that it will be useful, > > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > > + * GNU General Public License for more details. > > + * > > + * You should have received a copy of the GNU General Public License > > + * along with this program; if not, see . > > + */ > > + > > +#ifndef _LINUX_LIVEPATCH_H_ > > +#define _LINUX_LIVEPATCH_H_ > > + > > +#include > > + > > I think we need something like > > #if IS_ENABLED(CONFIG_LIVE_PATCHING) > > here. Otherwise kernel module with live patch itself would be built > even with live patching support disabled (as the structures and needed > functions are declared). What do you think of this (already includes s/lp/klp/ change)? ==== diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 0143b73..a9821f3 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -21,6 +21,7 @@ #define _LINUX_LIVEPATCH_H_ #include +#include /* TODO: add kernel-doc for structures once agreed upon */ @@ -58,11 +59,20 @@ struct klp_patch { struct klp_object *objs; }; -int klp_register_patch(struct klp_patch *); -int klp_unregister_patch(struct klp_patch *); -int klp_enable_patch(struct klp_patch *); -int klp_disable_patch(struct klp_patch *); +#ifdef CONFIG_LIVE_PATCHING -#include +extern int klp_register_patch(struct klp_patch *); +extern int klp_unregister_patch(struct klp_patch *); +extern int klp_enable_patch(struct klp_patch *); +extern int klp_disable_patch(struct klp_patch *); + +#else /* !CONFIG_LIVE_PATCHING */ + +static int klp_register_patch(struct klp_patch *k) { return -ENOSYS; } +static int klp_unregister_patch(struct klp_patch *k) { return -ENOSYS; } +static int klp_enable_patch(struct klp_patch *k) { return -ENOSYS; } +static int klp_disable_patch(struct klp_patch *k) { return -ENOSYS; } + +#endif ==== This seems to be the way many headers handle this. Patch modules built against a kernel that doesn't support live patching will build cleanly, but will always fail to load. Seth > > > +/* TODO: add kernel-doc for structures once agreed upon */ > > + > > +struct lp_func { > > + const char *old_name; /* function to be patched */ > > + void *new_func; /* replacement function in patch module */ > > + /* > > + * The old_addr field is optional and can be used to resolve > > + * duplicate symbol names in the vmlinux object. If this > > + * information is not present, the symbol is located by name > > + * with kallsyms. If the name is not unique and old_addr is > > + * not provided, the patch application fails as there is no > > + * way to resolve the ambiguity. > > + */ > > + unsigned long old_addr; > > +}; > > + > > +struct lp_reloc { > > + unsigned long dest; > > + unsigned long src; > > + unsigned long type; > > + const char *name; > > + int addend; > > + int external; > > +}; > > + > > +struct lp_object { > > + const char *name; /* "vmlinux" or module name */ > > + struct lp_func *funcs; > > + struct lp_reloc *relocs; > > +}; > > + > > +struct lp_patch { > > + struct module *mod; /* module containing the patch */ > > + struct lp_object *objs; > > +}; > > + > > +int lp_register_patch(struct lp_patch *); > > +int lp_unregister_patch(struct lp_patch *); > > +int lp_enable_patch(struct lp_patch *); > > +int lp_disable_patch(struct lp_patch *); > > + > > +#include > > and #endif for CONFIG_LIVE_PATCHING here. > > > + > > +#endif /* _LINUX_LIVEPATCH_H_ */ > > Thanks, > -- > Miroslav Benes > SUSE Labs -- 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/