[PATCH] x86: Improve handling of kernel mappings in change_page_attr

Fix various broken corner cases in i386 and x86-64 change_page_attr.

AK: split off from tighten kernel image access rights
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>

arch/i386/mm/pageattr.c

@@ -142,7 +142,7 @@ __change_page_attr(struct page *page, pgprot_t prot)
 		return -EINVAL;
 	kpte_page = virt_to_page(kpte);
 	if (pgprot_val(prot) != pgprot_val(PAGE_KERNEL)) { 
-		if ((pte_val(*kpte) & _PAGE_PSE) == 0) { 
+		if (!pte_huge(*kpte)) {
 			set_pte_atomic(kpte, mk_pte(page, prot)); 
 		} else {
 			pgprot_t ref_prot;
@@ -158,7 +158,7 @@ __change_page_attr(struct page *page, pgprot_t prot)
 			kpte_page = split;
 		}
 		page_private(kpte_page)++;
-	} else if ((pte_val(*kpte) & _PAGE_PSE) == 0) { 
+	} else if (!pte_huge(*kpte)) {
 		set_pte_atomic(kpte, mk_pte(page, PAGE_KERNEL));
 		BUG_ON(page_private(kpte_page) == 0);
 		page_private(kpte_page)--;

arch/x86_64/mm/pageattr.c

@@ -179,16 +179,24 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
 int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
 {
 	unsigned long phys_base_pfn = __pa_symbol(__START_KERNEL_map) >> PAGE_SHIFT;
-	int err = 0; 
+	int err = 0, kernel_map = 0;
 	int i; 
 
+	if (address >= __START_KERNEL_map
+	    && address < __START_KERNEL_map + KERNEL_TEXT_SIZE) {
+		address = (unsigned long)__va(__pa(address));
+		kernel_map = 1;
+	}
+
 	down_write(&init_mm.mmap_sem);
 	for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
 		unsigned long pfn = __pa(address) >> PAGE_SHIFT;
 
-		err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
-		if (err) 
-			break; 
+		if (!kernel_map || pte_present(pfn_pte(0, prot))) {
+			err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
+			if (err)
+				break;
+		}
 		/* Handle kernel mapping too which aliases part of the
 		 * lowmem */
 		if ((pfn >= phys_base_pfn) &&

include/asm-i386/pgtable.h

@@ -159,6 +159,7 @@ void paging_init(void);
 
 extern unsigned long long __PAGE_KERNEL, __PAGE_KERNEL_EXEC;
 #define __PAGE_KERNEL_RO		(__PAGE_KERNEL & ~_PAGE_RW)
+#define __PAGE_KERNEL_RX		(__PAGE_KERNEL_EXEC & ~_PAGE_RW)
 #define __PAGE_KERNEL_NOCACHE		(__PAGE_KERNEL | _PAGE_PCD)
 #define __PAGE_KERNEL_LARGE		(__PAGE_KERNEL | _PAGE_PSE)
 #define __PAGE_KERNEL_LARGE_EXEC	(__PAGE_KERNEL_EXEC | _PAGE_PSE)
@@ -166,6 +167,7 @@ extern unsigned long long __PAGE_KERNEL, __PAGE_KERNEL_EXEC;
 #define PAGE_KERNEL		__pgprot(__PAGE_KERNEL)
 #define PAGE_KERNEL_RO		__pgprot(__PAGE_KERNEL_RO)
 #define PAGE_KERNEL_EXEC	__pgprot(__PAGE_KERNEL_EXEC)
+#define PAGE_KERNEL_RX		__pgprot(__PAGE_KERNEL_RX)
 #define PAGE_KERNEL_NOCACHE	__pgprot(__PAGE_KERNEL_NOCACHE)
 #define PAGE_KERNEL_LARGE	__pgprot(__PAGE_KERNEL_LARGE)
 #define PAGE_KERNEL_LARGE_EXEC	__pgprot(__PAGE_KERNEL_LARGE_EXEC)