[PATCH] Fix pte_exec/mkexec and use it in change_page_attr()

Fix the pte_exec/mkexec page table accessor functions to really
use the NX bit. Previously they only checked the USER bit, but
weren't actually used for anything.

Then use them in change_page_attr() to manipulate the NX bit
properly.

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

2 files changed, 7 insertions, 5 deletions

diff --git a/arch/x86_64/mm/pageattr.c b/arch/x86_64/mm/pageattr.c
index 2685b1f3671c..01591b649f4e 100644
--- a/arch/x86_64/mm/pageattr.c
+++ b/arch/x86_64/mm/pageattr.c
@@ -190,10 +190,12 @@ int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
                  * lowmem */
                 if (__pa(address) < KERNEL_TEXT_SIZE) {
                         unsigned long addr2;
-                        pgprot_t prot2 = prot;
+                        pgprot_t prot2;
                         addr2 = __START_KERNEL_map + __pa(address);
-                        pgprot_val(prot2) &= ~_PAGE_NX;
-                        err = __change_page_attr(addr2, pfn, prot2, PAGE_KERNEL_EXEC);
+                        /* Make sure the kernel mappings stay executable */
+                        prot2 = pte_pgprot(pte_mkexec(pfn_pte(0, prot)));
+                        err = __change_page_attr(addr2, pfn, prot2,
+                                                 PAGE_KERNEL_EXEC);
                 } 
         }       
         up_write(&init_mm.mmap_sem); 
diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h
index d79e7441b513..f7614670c655 100644
--- a/include/asm-x86_64/pgtable.h
+++ b/include/asm-x86_64/pgtable.h
@@ -265,7 +265,7 @@ static inline pte_t pfn_pte(unsigned long page_nr, pgprot_t pgprot)
 #define __LARGE_PTE (_PAGE_PSE|_PAGE_PRESENT)
 static inline int pte_user(pte_t pte)           { return pte_val(pte) & _PAGE_USER; }
 static inline int pte_read(pte_t pte)           { return pte_val(pte) & _PAGE_USER; }
-static inline int pte_exec(pte_t pte)           { return pte_val(pte) & _PAGE_USER; }
+static inline int pte_exec(pte_t pte)           { return !(pte_val(pte) & _PAGE_NX); }
 static inline int pte_dirty(pte_t pte)          { return pte_val(pte) & _PAGE_DIRTY; }
 static inline int pte_young(pte_t pte)          { return pte_val(pte) & _PAGE_ACCESSED; }
 static inline int pte_write(pte_t pte)          { return pte_val(pte) & _PAGE_RW; }
@@ -278,7 +278,7 @@ static inline pte_t pte_mkclean(pte_t pte)	{ set_pte(&pte, __pte(pte_val(pte) &
 static inline pte_t pte_mkold(pte_t pte)        { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_ACCESSED)); return pte; }
 static inline pte_t pte_wrprotect(pte_t pte)    { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_RW)); return pte; }
 static inline pte_t pte_mkread(pte_t pte)       { set_pte(&pte, __pte(pte_val(pte) | _PAGE_USER)); return pte; }
-static inline pte_t pte_mkexec(pte_t pte)       { set_pte(&pte, __pte(pte_val(pte) | _PAGE_USER)); return pte; }
+static inline pte_t pte_mkexec(pte_t pte)       { set_pte(&pte, __pte(pte_val(pte) & ~_PAGE_NX)); return pte; }
 static inline pte_t pte_mkdirty(pte_t pte)      { set_pte(&pte, __pte(pte_val(pte) | _PAGE_DIRTY)); return pte; }
 static inline pte_t pte_mkyoung(pte_t pte)      { set_pte(&pte, __pte(pte_val(pte) | _PAGE_ACCESSED)); return pte; }
 static inline pte_t pte_mkwrite(pte_t pte)      { set_pte(&pte, __pte(pte_val(pte) | _PAGE_RW)); return pte; }