Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751762AbbKJE1i (ORCPT ); Mon, 9 Nov 2015 23:27:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48489 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751107AbbKJE1h (ORCPT ); Mon, 9 Nov 2015 23:27:37 -0500 Date: Mon, 9 Nov 2015 22:27:36 -0600 From: Josh Poimboeuf To: Rusty Russell Cc: linux-kernel@vger.kernel.org, Peter Zijlstra Subject: Re: [PATCH 4/4] module: clean up RO/NX handling. Message-ID: <20151110042736.GA18117@treble.hsd1.ky.comcast.net> References: <1447043037-10833-1-git-send-email-rusty@rustcorp.com.au> <1447043037-10833-5-git-send-email-rusty@rustcorp.com.au> <20151109195153.GB3914@treble.redhat.com> <87611ak44x.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87611ak44x.fsf@rustcorp.com.au> 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 Content-Length: 2229 Lines: 53 On Tue, Nov 10, 2015 at 12:27:34PM +1030, Rusty Russell wrote: > Josh Poimboeuf writes: > > On Mon, Nov 09, 2015 at 02:53:57PM +1030, Rusty Russell wrote: > > > >> @@ -1858,74 +1849,75 @@ static void mod_sysfs_teardown(struct module *mod) > >> /* > >> * LKM RO/NX protection: protect module's text/ro-data > >> * from modification and any data from execution. > >> + * > >> + * General layout of module is: > >> + * [text] [read-only-data] [writable data] > >> + * text_size -----^ ^ ^ > >> + * ro_size ------------------------| | > >> + * size -------------------------------------------| > >> + * > >> + * These values are always page-aligned (as is base) > >> */ > >> -void set_page_attributes(void *start, void *end, int (*set)(unsigned long start, int num_pages)) > >> +static void frob_text(const struct module_layout *layout, > >> + int (*set_memory)(unsigned long start, int num_pages)) > >> { > >> - unsigned long begin_pfn = PFN_DOWN((unsigned long)start); > >> - unsigned long end_pfn = PFN_DOWN((unsigned long)end); > >> - > >> - if (end_pfn > begin_pfn) > >> - set(begin_pfn << PAGE_SHIFT, end_pfn - begin_pfn); > >> + BUG_ON((unsigned long)layout->base & (PAGE_SIZE-1)); > >> + BUG_ON((unsigned long)layout->text_size & (PAGE_SIZE-1)); > >> + set_memory((unsigned long)layout->base, > >> + layout->text_size >> PAGE_SHIFT); > > > > Should the set_memory() call be skipped if text_size is 0? > > Not AFAICT. And in practice: > 1) Every module on my system has a .text section. > 2) Every module has a rodata section (.modinfo) > 3) Every module on my system has a .data section. > > So I think it would be a premature optimization. However, the frob functions are also used for init sections. A search on my Fedora system's modules for .init.* sections shows that most modules don't have .init.rodata and .init.data, and some modules don't even have .init.text. -- Josh -- 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/