[patch] mark text section read-only

[Coywolf Qi Hunt <coywolf@sosdg.org>]

On Sat, Nov 12, 2005 at 02:57:02AM +0800, Coywolf Qi Hunt wrote:
> And we could also mark text section read-only and data/stack section
> noexec if NX is supported. But I doubt the whole thing would really
> help much. Kill the kernel thread? We can't. We only run into a panic.
> Anyway I'd attach a quick patch to mark text section read only in the
> next mail.
> 
> If it's ok, I'd add Kconfig support. Comments?


Signed-off-by: Coywolf Qi Hunt <qiyong@fc-cn.com>
---

diff -pruN 2.6.14-mm2/init/main.c 2.6.14-mm2-cy/init/main.c
--- 2.6.14-mm2/init/main.c	2005-11-11 22:34:21.000000000 +0800
+++ 2.6.14-mm2-cy/init/main.c	2005-11-12 02:50:45.000000000 +0800
@@ -660,6 +660,18 @@ static inline void fixup_cpu_present_map
 #endif
 }
 
+void mark_text_ro(void)
+{
+	unsigned long addr = (unsigned long)&_text;
+
+	for (; addr < (unsigned long)&_etext; addr += PAGE_SIZE)
+		change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);
+	
+	printk ("Write protecting the kernel text data: %luk\n",
+			(unsigned long)(_etext - _text) >> 10);
+	global_flush_tlb();
+}
+
 static int init(void * unused)
 {
 	lock_kernel();
@@ -716,6 +728,7 @@ static int init(void * unused)
 	 */
 	free_initmem();
 	unlock_kernel();
+	mark_text_ro();
 	mark_rodata_ro();
 	system_state = SYSTEM_RUNNING;
 	numa_default_policy();