uml: use get_free_pages to allocate kernel stacks

For some reason, I was using kmalloc instead of get_free_pages for kernel
stacks.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/asm-um/thread_info.h

@@ -54,8 +54,10 @@ static inline struct thread_info *current_thread_info(void)
 
 /* thread information allocation */
 #define alloc_thread_info(tsk) \
-	((struct thread_info *) kmalloc(THREAD_SIZE, GFP_KERNEL))
-#define free_thread_info(ti) kfree(ti)
+	((struct thread_info *) __get_free_pages(GFP_KERNEL, \
+						 CONFIG_KERNEL_STACK_ORDER))
+#define free_thread_info(ti) \
+	free_pages((unsigned long)(ti),CONFIG_KERNEL_STACK_ORDER)
 
 #endif