m68k: use addr_limit checking for m68k CPUs that do no support address spaces

The ColdFire CPU family, and the original 68000, do not support separate
address spaces like the other 680x0 CPU types. Modify the set_fs()/get_fs()
functions and macros to use a thread_info addr_limit for address space
checking. This is pretty much what all other architectures that do not
support separate setable address spaces do.
Signed-off-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Acked-by: Matt Waddel <mwaddel@yahoo.com>
Acked-by: Kurt Mahan <kmahan@xmission.com>

arch/m68k/include/asm/segment.h

@@ -22,23 +22,26 @@ typedef struct {
 } mm_segment_t;
 
 #define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
-#define USER_DS		MAKE_MM_SEG(__USER_DS)
-#define KERNEL_DS	MAKE_MM_SEG(__KERNEL_DS)
 
+#ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
 /*
  * Get/set the SFC/DFC registers for MOVES instructions
  */
+#define USER_DS		MAKE_MM_SEG(__USER_DS)
+#define KERNEL_DS	MAKE_MM_SEG(__KERNEL_DS)
 
 static inline mm_segment_t get_fs(void)
 {
-#ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
 	mm_segment_t _v;
 	__asm__ ("movec %/dfc,%0":"=r" (_v.seg):);
-
 	return _v;
-#else
-	return USER_DS;
-#endif
+}
+
+static inline void set_fs(mm_segment_t val)
+{
+	__asm__ __volatile__ ("movec %0,%/sfc\n\t"
+			      "movec %0,%/dfc\n\t"
+			      : /* no outputs */ : "r" (val.seg) : "memory");
 }
 
 static inline mm_segment_t get_ds(void)
@@ -47,14 +50,13 @@ static inline mm_segment_t get_ds(void)
     return KERNEL_DS;
 }
 
-static inline void set_fs(mm_segment_t val)
-{
-#ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
-	__asm__ __volatile__ ("movec %0,%/sfc\n\t"
-			      "movec %0,%/dfc\n\t"
-			      : /* no outputs */ : "r" (val.seg) : "memory");
+#else
+#define USER_DS		MAKE_MM_SEG(TASK_SIZE)
+#define KERNEL_DS	MAKE_MM_SEG(0xFFFFFFFF)
+#define get_ds()	(KERNEL_DS)
+#define get_fs()	(current_thread_info()->addr_limit)
+#define set_fs(x)	(current_thread_info()->addr_limit = (x))
 #endif
-}
 
 #define segment_eq(a,b)	((a).seg == (b).seg)
 

arch/m68k/include/asm/thread_info.h

@@ -3,6 +3,7 @@
 
 #include <asm/types.h>
 #include <asm/page.h>
+#include <asm/segment.h>
 
 /*
  * On machines with 4k pages we default to an 8k thread size, though we
@@ -26,6 +27,7 @@ struct thread_info {
 	struct task_struct	*task;		/* main task structure */
 	unsigned long		flags;
 	struct exec_domain	*exec_domain;	/* execution domain */
+	mm_segment_t		addr_limit;	/* thread address space */
 	int			preempt_count;	/* 0 => preemptable, <0 => BUG */
 	__u32			cpu;		/* should always be 0 on m68k */
 	unsigned long		tp_value;	/* thread pointer */
@@ -39,6 +41,7 @@ struct thread_info {
 {						\
 	.task		= &tsk,			\
 	.exec_domain	= &default_exec_domain,	\
+	.addr_limit	= KERNEL_DS,		\
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 	.restart_block = {			\
 		.fn = do_no_restart_syscall,	\