[PATCH] uml: fix broken #ifdef clause causing crashes

The previous ifdef to check whether to use the host's vsyscall page was buggy.
This bug can cause crashes.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/um/Kconfig_i386

@@ -18,3 +18,7 @@ config 3_LEVEL_PGTABLES
 config ARCH_HAS_SC_SIGNALS
 	bool
 	default y
+
+config ARCH_REUSE_HOST_VSYSCALL_AREA
+	bool
+	default y

arch/um/Kconfig_x86_64

@@ -9,3 +9,7 @@ config 3_LEVEL_PGTABLES
 config ARCH_HAS_SC_SIGNALS
 	bool
 	default n
+
+config ARCH_REUSE_HOST_VSYSCALL_AREA
+	bool
+	default n

arch/um/kernel/mem.c

@@ -152,6 +152,7 @@ void __init kmap_init(void)
 static void init_highmem(void)
 {
 	pgd_t *pgd;
+	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	unsigned long vaddr;
@@ -163,7 +164,8 @@ static void init_highmem(void)
 	fixrange_init(vaddr, vaddr + PAGE_SIZE*LAST_PKMAP, swapper_pg_dir);
 
 	pgd = swapper_pg_dir + pgd_index(vaddr);
-	pmd = pmd_offset(pgd, vaddr);
+	pud = pud_offset(pgd, vaddr);
+	pmd = pmd_offset(pud, vaddr);
 	pte = pte_offset_kernel(pmd, vaddr);
 	pkmap_page_table = pte;
 
@@ -173,9 +175,10 @@ static void init_highmem(void)
 
 static void __init fixaddr_user_init( void)
 {
-#if FIXADDR_USER_START != 0
+#if CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
 	long size = FIXADDR_USER_END - FIXADDR_USER_START;
 	pgd_t *pgd;
+	pud_t *pud;
 	pmd_t *pmd;
 	pte_t *pte;
 	unsigned long paddr, vaddr = FIXADDR_USER_START;
@@ -187,9 +190,10 @@ static void __init fixaddr_user_init( void)
 	paddr = (unsigned long)alloc_bootmem_low_pages( size);
 	memcpy( (void *)paddr, (void *)FIXADDR_USER_START, size);
 	paddr = __pa(paddr);
-	for ( ; size > 0; size-=PAGE_SIZE, vaddr+=PAGE_SIZE, paddr+=PAGE_SIZE) {
+	for ( ; size > 0; size-=PAGE_SIZE, vaddr+=PAGE_SIZE, paddr+=PAGE_SIZE){
 		pgd = swapper_pg_dir + pgd_index(vaddr);
-		pmd = pmd_offset(pgd, vaddr);
+		pud = pud_offset(pgd, vaddr);
+		pmd = pmd_offset(pud, vaddr);
 		pte = pte_offset_kernel(pmd, vaddr);
 		pte_set_val( (*pte), paddr, PAGE_READONLY);
 	}