uml: clean up TASK_SIZE usage

Clean up the calculation and use of the usable address space size on the host.

task_size is gone, replaced with TASK_SIZE, which is calculated from
CONFIG_TOP_ADDR.  get_kmem_end and set_task_sizes_skas are also gone.

host_task_size, which refers to the entire address space usable by the UML
kernel and which may be larger than the address space usable by a UML process,
since that has to end on a pgdir boundary, is replaced by CONFIG_TOP_ADDR.

STACK_TOP is now TASK_SIZE minus the two stub pages.

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/a.out.h

@@ -13,11 +13,9 @@
 
 extern unsigned long stacksizelim;
 
-extern unsigned long host_task_size;
-
 #define STACK_ROOM (stacksizelim)
 
-#define STACK_TOP task_size
+#define STACK_TOP (TASK_SIZE - 2 * PAGE_SIZE)
 
 #define STACK_TOP_MAX STACK_TOP
 

include/asm-um/fixmap.h

@@ -56,9 +56,8 @@ extern void __set_fixmap (enum fixed_addresses idx,
  * the start of the fixmap, and leave one page empty
  * at the top of mem..
  */
-extern unsigned long get_kmem_end(void);
 
-#define FIXADDR_TOP	(get_kmem_end() - 0x2000)
+#define FIXADDR_TOP	(CONFIG_TOP_ADDR - 2 * PAGE_SIZE)
 #define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)
 

include/asm-um/processor-generic.h

@@ -94,9 +94,7 @@ static inline void mm_copy_segments(struct mm_struct *from_mm,
 /*
  * User space process size: 3GB (default).
  */
-extern unsigned long task_size;
-
-#define TASK_SIZE	(task_size)
+#define TASK_SIZE (CONFIG_TOP_ADDR & PGDIR_MASK)
 
 /* This decides where the kernel will search for a free chunk of vm
  * space during mmap's.