Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 19 Sep 2002 23:57:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 19 Sep 2002 23:57:38 -0400 Received: from dp.samba.org ([66.70.73.150]:39121 "EHLO lists.samba.org") by vger.kernel.org with ESMTP id ; Thu, 19 Sep 2002 23:57:36 -0400 From: Rusty Russell To: Greg KH Cc: linux-kernel@vger.kernel.org, Roman Zippel Subject: Re: [PATCH] In-kernel module loader 1/7 In-reply-to: Your message of "Thu, 19 Sep 2002 11:38:43 MST." <20020919183843.GA16568@kroah.com> Date: Fri, 20 Sep 2002 11:22:08 +1000 Message-Id: <20020920040241.4C03F2C0D9@lists.samba.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1857 Lines: 53 In message <20020919183843.GA16568@kroah.com> you write: > On Thu, Sep 19, 2002 at 03:54:40PM +0200, Roman Zippel wrote: > > I already said often enough, a module has only to answer the simple > > question: Is it safe to unload the module? > > And with a LSM module, how can it answer that? There's no way, unless > we count every time someone calls into our module. And if you do that, > no one will even want to use your module, given the number of hooks, and > the paths those hooks are on (the speed hit would be horrible.) Well, it's up to you. You *could* implement: #define call_security(method , ...) \ ({ int __ret; \ if (try_module_get(security_ops->owner)) { \ __ret = security_ops->method(__VA_ARGS__); \ module_put(security_ops->owner); \ } else \ /* If unloading or loading, default to "allow" */ \ __ret = 0; \ __ret; \ }) Now, if you don't have CONFIG_MODULES this becomes the code as it is now. If you don't have CONFIG_MODULE_UNLOAD, this becomes: if (security_ops->owner && security_ops->owner->live) __ret = security_ops->method(__VA_ARGS__); else __ret = 0; With the case of CONFIG_MODULE_UNLOAD, it looks *really* horrible (53 instructions with 6 branches: ewww...). So I would recommend register_security insert a shim and take the hit itself: #ifdef CONFIG_MODULE_UNLOAD if (ops->owner) { module_ops->real = ops; ops = module_ops; } #endif Then module_ops does the inc/dec wrappers (well, it can optimize if the ops can't sleep...). Rusty. -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell. - 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/