riscv: remove address space overrides using set_fs()

Stop providing the possibility to override the address space using
set_fs() now that there is no need for that any more.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

Author: Christoph Hellwig

arch/riscv/Kconfig

@@ -87,7 +87,6 @@ config RISCV
 	select SPARSE_IRQ
 	select SYSCTL_EXCEPTION_TRACE
 	select THREAD_INFO_IN_TASK
-	select SET_FS
 	select UACCESS_MEMCPY if !MMU
 
 config ARCH_MMAP_RND_BITS_MIN

arch/riscv/include/asm/thread_info.h

@@ -24,10 +24,6 @@
 #include <asm/processor.h>
 #include <asm/csr.h>
 
-typedef struct {
-	unsigned long seg;
-} mm_segment_t;
-
 /*
  * low level task data that entry.S needs immediate access to
  * - this struct should fit entirely inside of one cache line
@@ -39,7 +35,6 @@ typedef struct {
 struct thread_info {
 	unsigned long		flags;		/* low level flags */
 	int                     preempt_count;  /* 0=>preemptible, <0=>BUG */
-	mm_segment_t		addr_limit;
 	/*
 	 * These stack pointers are overwritten on every system call or
 	 * exception.  SP is also saved to the stack it can be recovered when
@@ -59,7 +54,6 @@ struct thread_info {
 {						\
 	.flags		= 0,			\
 	.preempt_count	= INIT_PREEMPT_COUNT,	\
-	.addr_limit	= KERNEL_DS,		\
 }
 
 #endif /* !__ASSEMBLY__ */

arch/riscv/include/asm/uaccess.h

@@ -26,29 +26,6 @@
 #define __disable_user_access()							\
 	__asm__ __volatile__ ("csrc sstatus, %0" : : "r" (SR_SUM) : "memory")
 
-/*
- * 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.
- *
- * For historical reasons, these macros are grossly misnamed.
- */
-
-#define MAKE_MM_SEG(s)	((mm_segment_t) { (s) })
-
-#define KERNEL_DS	MAKE_MM_SEG(~0UL)
-#define USER_DS		MAKE_MM_SEG(TASK_SIZE)
-
-#define get_fs()	(current_thread_info()->addr_limit)
-
-static inline void set_fs(mm_segment_t fs)
-{
-	current_thread_info()->addr_limit = fs;
-}
-
-#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
-#define user_addr_max()	(get_fs().seg)
-
 /**
  * access_ok: - Checks if a user space pointer is valid
  * @addr: User space pointer to start of block to check
@@ -76,9 +53,7 @@ static inline void set_fs(mm_segment_t fs)
  */
 static inline int __access_ok(unsigned long addr, unsigned long size)
 {
-	const mm_segment_t fs = get_fs();
-
-	return size <= fs.seg && addr <= fs.seg - size;
+	return size <= TASK_SIZE && addr <= TASK_SIZE - size;
 }
 
 /*

arch/riscv/kernel/process.c

@@ -84,7 +84,6 @@ void start_thread(struct pt_regs *regs, unsigned long pc,
 	}
 	regs->epc = pc;
 	regs->sp = sp;
-	set_fs(USER_DS);
 }
 
 void flush_thread(void)