From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764452AbXGNUJO (ORCPT ); Sat, 14 Jul 2007 16:09:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761351AbXGNUI7 (ORCPT ); Sat, 14 Jul 2007 16:08:59 -0400 Received: from tomts16-srv.bellnexxia.net ([209.226.175.4]:34290 "EHLO tomts16-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760924AbXGNUI7 (ORCPT ); Sat, 14 Jul 2007 16:08:59 -0400 Date: Sat, 14 Jul 2007 16:08:57 -0400 From: Mathieu Desnoyers To: Christoph Hellwig , akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH] Text Edit Lock - i386 Use kernel_text_is_ro Message-ID: <20070714200857.GP6975@Krystal> References: <20070714012133.612727310@polymtl.ca> <20070714012412.380213021@polymtl.ca> <20070714161831.GA13831@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <20070714161831.GA13831@infradead.org> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.21.3-grsec (i686) X-Uptime: 15:59:34 up 7 days, 10:04, 2 users, load average: 0.04, 0.14, 0.24 User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Text Edit Lock - i386 use kernel_text_is_ro * Christoph Hellwig (hch@infradead.org) wrote: > On Fri, Jul 13, 2007 at 09:21:36PM -0400, Mathieu Desnoyers wrote: > > +#ifdef CONFIG_DEBUG_RODATA > > +static int rodata_marked; > > +#endif > > Maybe I'm missing something, but the rodata section should always stay > r/o, only text needs locking/unlocking, no? > > Given that all code in this patch only operates on .text this seems fine, > but the variables/config options are grossly misnamed then. And actually > making rodata r/o doesn't seem like a pure debugging thing to me either. I think it will change to two different config options eventually (RO data and RO text). But for now, it makes more sense to use the kernel_text_is_ro variable. And since we do not plan to call kernel_text_mark_rw()/kernel_text_unmark() in the middle of mark_rodata_ro (we are still at boot time), there is no need to wait until after global_flush_tlb() mark the rodata. And it makes to rename mark_rodata_ro into kernel_rodata_is_ro. Signed-off-by: Mathieu Desnoyers CC: hch@infradead.org --- arch/i386/mm/init.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) Index: linux-2.6-lttng/arch/i386/mm/init.c =================================================================== --- linux-2.6-lttng.orig/arch/i386/mm/init.c 2007-07-14 16:04:20.000000000 -0400 +++ linux-2.6-lttng/arch/i386/mm/init.c 2007-07-14 16:05:45.000000000 -0400 @@ -47,6 +47,7 @@ #include int kernel_text_is_ro; +int kernel_rodata_is_ro; unsigned int __VMALLOC_RESERVE = 128 << 20; DEFINE_PER_CPU(struct mmu_gather, mmu_gathers); @@ -54,9 +55,6 @@ unsigned long highstart_pfn, highend_pfn static int noinline do_test_wp_bit(void); -#ifdef CONFIG_DEBUG_RODATA -static int rodata_marked; -#endif /* * Creates a middle page table and puts a pointer to it in the @@ -817,6 +815,7 @@ void mark_rodata_ro(void) size >> PAGE_SHIFT, PAGE_KERNEL_RO); printk("Write protecting the kernel read-only data: %luk\n", size >> 10); + kernel_rodata_is_ro = 1; /* * change_page_attr() requires a global_flush_tlb() call after it. @@ -825,7 +824,6 @@ void mark_rodata_ro(void) * of who is the culprit. */ global_flush_tlb(); - rodata_marked = 1; } /* @@ -834,7 +832,7 @@ void mark_rodata_ro(void) */ void __kprobes kernel_text_mark_rw(unsigned long address, size_t len) { - if (rodata_marked && address >= PFN_ALIGN(_text) + if (kernel_text_is_ro && address >= PFN_ALIGN(_text) && (address + len) <= PFN_ALIGN(_etext)) { unsigned long nr_pages; nr_pages = ((address + len) >> PAGE_SHIFT) @@ -851,7 +849,7 @@ EXPORT_SYMBOL_GPL(kernel_text_mark_rw); void __kprobes kernel_text_unmark(unsigned long address, size_t len) { - if (rodata_marked && address >= PFN_ALIGN(_text) + if (kernel_text_is_ro && address >= PFN_ALIGN(_text) && (address + len) <= PFN_ALIGN(_etext)) { unsigned long nr_pages; nr_pages = ((address + len) >> PAGE_SHIFT) -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68