uaccess: remove CONFIG_SET_FS

There are no remaining callers of set_fs(), so CONFIG_SET_FS
can be removed globally, along with the thread_info field and
any references to it.

This turns access_ok() into a cheaper check against TASK_SIZE_MAX.

As CONFIG_SET_FS is now gone, drop all remaining references to
set_fs()/get_fs(), mm_segment_t, user_addr_max() and uaccess_kernel().

Acked-by: Sam Ravnborg <sam@ravnborg.org> # for sparc32 changes
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Tested-by: Sergey Matyukevich <sergey.matyukevich@synopsys.com> # for arc changes
Acked-by: Stafford Horne <shorne@gmail.com> # [openrisc, asm-generic]
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/alpha/include/asm/processor.h

@@ -26,10 +26,6 @@
 #define TASK_UNMAPPED_BASE \
   ((current->personality & ADDR_LIMIT_32BIT) ? 0x40000000 : TASK_SIZE / 2)
 
-typedef struct {
-	unsigned long seg;
-} mm_segment_t;
-
 /* This is dead.  Everything has been moved to thread_info.  */
 struct thread_struct { };
 #define INIT_THREAD  { }

arch/alpha/include/asm/thread_info.h

@@ -19,7 +19,6 @@ struct thread_info {
 	unsigned int		flags;		/* low level flags */
 	unsigned int		ieee_state;	/* see fpu.h */
 
-	mm_segment_t		addr_limit;	/* thread address space */
 	unsigned		cpu;		/* current CPU */
 	int			preempt_count; /* 0 => preemptable, <0 => BUG */
 	unsigned int		status;		/* thread-synchronous flags */
@@ -35,7 +34,6 @@ struct thread_info {
 #define INIT_THREAD_INFO(tsk)			\
 {						\
 	.task		= &tsk,			\
-	.addr_limit	= KERNEL_DS,		\
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
 }
 

arch/alpha/include/asm/uaccess.h

@@ -2,26 +2,7 @@
 #ifndef __ALPHA_UACCESS_H
 #define __ALPHA_UACCESS_H
 
-/*
- * The fs value determines whether argument validity checking should be
- * performed or not.  If get_fs() == USER_DS, checking is performed, with
- * get_fs() == KERNEL_DS, checking is bypassed.
- *
- * Or at least it did once upon a time.  Nowadays it is a mask that
- * defines which bits of the address space are off limits.  This is a
- * wee bit faster than the above.
- *
- * For historical reasons, these macros are grossly misnamed.
- */
-
-#define KERNEL_DS	((mm_segment_t) { 0UL })
-#define USER_DS		((mm_segment_t) { -0x40000000000UL })
-
-#define get_fs()  (current_thread_info()->addr_limit)
-#define set_fs(x) (current_thread_info()->addr_limit = (x))
-
 #include <asm-generic/access_ok.h>
-
 /*
  * These are the main single-value transfer routines.  They automatically
  * use the right size if we just have the right pointer type.