[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>

3 files changed, 16 insertions, 6 deletions

diff --git a/arch/i386/mm/pageattr.c b/arch/i386/mm/pageattr.c
index 412ebbd8adb0..ea6b6d4a0a2a 100644
--- a/arch/i386/mm/pageattr.c
+++ b/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)--;
diff --git a/arch/x86_64/mm/pageattr.c b/arch/x86_64/mm/pageattr.c
index 76ee90a5abe0..bf4aa8dd4254 100644
--- a/arch/x86_64/mm/pageattr.c
+++ b/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) &&
diff --git a/include/asm-i386/pgtable.h b/include/asm-i386/pgtable.h
index c3b58d473a55..143ddc42b86f 100644
--- a/include/asm-i386/pgtable.h
+++ b/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)