On Tue, Jul 03, 2007 at 12:38:22PM -0400, Mathieu Desnoyers wrote: > Kprobes can use the text edit lock to insure mutual exclusion when edition the > code and make sure the pages are writable.
Linus suggested for splitting ro-data and ro-text; And allow ro-text only if kprobes is not configured. Please see the discussion thread, URL given below http://lkml.org/lkml/2007/6/20/436 This patch below allows to configure and mark the kernel text and kernel data as read-only separately. Also kernel text is configured read-only if kprobes is not configured. Thanks Prasanna This patch allows to configure and mark the kernel text and kernel data as read-only separately. Signed-off-by: Prasanna S P. <[EMAIL PROTECTED]> arch/i386/Kconfig.debug | 8 ++++++++ arch/i386/mm/init.c | 22 ++++++++++++++++------ 2 files changed, 24 insertions(+), 6 deletions(-) diff -puN arch/i386/Kconfig.debug~mark-kernel-text-data-ro-seperately-i386 arch/i386/Kconfig.debug --- linux-2.6.22-rc6/arch/i386/Kconfig.debug~mark-kernel-text-data-ro-seperately-i386 2007-07-04 13:45:24.000000000 +0530 +++ linux-2.6.22-rc6-prasanna/arch/i386/Kconfig.debug 2007-07-04 13:52:31.000000000 +0530 @@ -56,6 +56,14 @@ config DEBUG_RODATA portion of the kernel code won't be covered by a 2MB TLB anymore. If in doubt, say "N". +config DEBUG_ROTEXT + bool "Write protect kernel text" + depends on DEBUG_RODATA && !KPROBES + help + Mark the kernel text as write-protected in the pagetables. + Only allow this if kprobes is not configured. + If in doubt, say "N". + config 4KSTACKS bool "Use 4Kb for kernel stacks instead of 8Kb" depends on DEBUG_KERNEL diff -puN arch/i386/mm/init.c~mark-kernel-text-data-ro-seperately-i386 arch/i386/mm/init.c --- linux-2.6.22-rc6/arch/i386/mm/init.c~mark-kernel-text-data-ro-seperately-i386 2007-07-04 13:45:24.000000000 +0530 +++ linux-2.6.22-rc6-prasanna/arch/i386/mm/init.c 2007-07-04 13:51:39.000000000 +0530 @@ -792,14 +792,11 @@ static int noinline do_test_wp_bit(void) return flag; } -#ifdef CONFIG_DEBUG_RODATA - -void mark_rodata_ro(void) +static inline void mark_rwtext_ro(void) { unsigned long start = PFN_ALIGN(_text); unsigned long size = PFN_ALIGN(_etext) - start; -#ifndef CONFIG_KPROBES #ifdef CONFIG_HOTPLUG_CPU /* It must still be possible to apply SMP alternatives. */ if (num_possible_cpus() <= 1) @@ -809,9 +806,22 @@ void mark_rodata_ro(void) size >> PAGE_SHIFT, PAGE_KERNEL_RX); printk("Write protecting the kernel text: %luk\n", size >> 10); } + + /* + * global_flush_tlb() will be called after marking the data as readonly. + */ +} + +#ifdef CONFIG_DEBUG_RODATA + +void mark_rodata_ro(void) +{ + unsigned long start = PFN_ALIGN(_etext); + unsigned long size = (unsigned long)__end_rodata - start; + +#ifdef CONFIG_DEBUG_ROTEXT + mark_rwtext_ro(); #endif - start += size; - size = (unsigned long)__end_rodata - start; change_page_attr(virt_to_page(start), size >> PAGE_SHIFT, PAGE_KERNEL_RO); printk("Write protecting the kernel read-only data: %luk\n", _ -- Prasanna S.P. Linux Technology Center India Software Labs, IBM Bangalore Email: [EMAIL PROTECTED] Ph: 91-80-41776329 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
