x86_32: remove __PAGE_KERNEL(_EXEC)

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Older x86-32 processors do not support global mappings (PGD), so must
only use it if the processor supports it.

The _PAGE_KERNEL* flags always have _PAGE_KERNEL set, since logically
we always want it set.

This is OK even on processors which do not support PGD, since all
_PAGE flags are masked with __supported_pte_mask before being turned
into a real in-pagetable pte.  On 32-bit systems, __supported_pte_mask
is initialized to not contain _PAGE_GLOBAL, and it is then added if
the CPU is found to support it.

The x86-32 code used to use __PAGE_KERNEL/__PAGE_KERNEL_EXEC for this
purpose, but they're now redundant and can be removed.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 2 insertions, 18 deletions

diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c
index 8efe872b9617..b5a0fd5f4c5f 100644
--- a/arch/x86/mm/init_32.c
+++ b/arch/x86/mm/init_32.c
@@ -383,11 +383,6 @@ static void __init set_highmem_pages_init(void)
 # define set_highmem_pages_init()       do { } while (0)
 #endif /* CONFIG_HIGHMEM */
 
-pteval_t __PAGE_KERNEL = _PAGE_KERNEL;
-EXPORT_SYMBOL(__PAGE_KERNEL);
-
-pteval_t __PAGE_KERNEL_EXEC = _PAGE_KERNEL_EXEC;
-
 void __init native_pagetable_setup_start(pgd_t *base)
 {
         unsigned long pfn, va;
@@ -509,7 +504,7 @@ void zap_low_mappings(void)
 
 int nx_enabled;
 
-pteval_t __supported_pte_mask __read_mostly = ~_PAGE_NX;
+pteval_t __supported_pte_mask __read_mostly = ~(_PAGE_NX | _PAGE_GLOBAL);
 EXPORT_SYMBOL_GPL(__supported_pte_mask);
 
 #ifdef CONFIG_X86_PAE
@@ -796,8 +791,7 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
         /* Enable PGE if available */
         if (cpu_has_pge) {
                 set_in_cr4(X86_CR4_PGE);
-                __PAGE_KERNEL |= _PAGE_GLOBAL;
-                __PAGE_KERNEL_EXEC |= _PAGE_GLOBAL;
+                __supported_pte_mask |= _PAGE_GLOBAL;
         }
 
         /*
diff --git a/include/asm-x86/pgtable.h b/include/asm-x86/pgtable.h
index a1c0009e81b7..64de07e25329 100644
--- a/include/asm-x86/pgtable.h
+++ b/include/asm-x86/pgtable.h
@@ -78,19 +78,9 @@
 #define PAGE_READONLY_EXEC      __pgprot(_PAGE_PRESENT | _PAGE_USER |   \
                                          _PAGE_ACCESSED)
 
-#ifdef CONFIG_X86_32
-#define _PAGE_KERNEL_EXEC \
-        (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED)
-#define _PAGE_KERNEL (_PAGE_KERNEL_EXEC | _PAGE_NX)
-
-#ifndef __ASSEMBLY__
-extern pteval_t __PAGE_KERNEL, __PAGE_KERNEL_EXEC;
-#endif  /* __ASSEMBLY__ */
-#else
 #define __PAGE_KERNEL_EXEC                                              \
         (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_GLOBAL)
 #define __PAGE_KERNEL           (__PAGE_KERNEL_EXEC | _PAGE_NX)
-#endif
 
 #define __PAGE_KERNEL_RO                (__PAGE_KERNEL & ~_PAGE_RW)
 #define __PAGE_KERNEL_RX                (__PAGE_KERNEL_EXEC & ~_PAGE_RW)