[PATCH] [29/31] CPA: Add a BUG_ON checking for someone setting the kernel text NX

Andi Kleen
2008-01-14T22:27:38Z

Someone setting NX on the kernel text tends to result in nasty failures
and triple faults, so BUG_ON early for that.

Does not cover __inittext.

Signed-off-by: Andi Kleen <ak@suse.de>

---
arch/x86/mm/pageattr_32.c | 8 ++++++++
1 file changed, 8 insertions(+)

Index: linux/arch/x86/mm/pageattr_32.c
===================================================================
--- linux.orig/arch/x86/mm/pageattr_32.c
+++ linux/arch/x86/mm/pageattr_32.c
@@ -242,6 +242,14 @@ __change_page_attr(struct page *page, pg
BUG_ON(PageLRU(kpte_page));
BUG_ON(PageCompound(kpte_page));

+ /*
+ * Better fail early if someone sets the kernel text to NX.
+ * Does not cover __inittext
+ */
+ BUG_ON(address >= (unsigned long)&_text &&
+ address < (unsigned long)&_etext &&
+ (pgprot_val(prot) & _PAGE_NX));
+
set_tlb_flush(address, cache_attr_changed(*kpte, prot, level),
level < 3);