x86/uaccess: Remove __get_user() and __put_user()uaccess-cleanups

Nothing that builds on x86 uses __get_user() or __put_user() any more.
They were the "unchecked" user accessors: no range check, on the
assumption that the caller had already done an access_ok().  That
stopped buying anything once every user access had to be enabled and
disabled on its own, and on x86 __get_user() had become slower than
get_user(), since it does an lfence where get_user() checks the address
with a couple of plain instructions.  Several of the last users were
also relying on them for things they were never meant to do: accessing
kernel addresses, or staying quiet in atomic context.

Remove the macros and the out-of-line __{get,put}_user_nocheck_N helpers
behind them, so that new users cannot appear.

Other architectures still provide their own versions.  UML gets its
accessors from asm-generic and is not affected.  arm64's __get_user()
and __put_user() have always been the same as get_user() and put_user(),
so there is no hurry there.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 10 insertions, 166 deletions

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3a0dd3c2b233..f4700ad6b5ec 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -28,10 +28,6 @@ extern int __get_user_1(void);
 extern int __get_user_2(void);
 extern int __get_user_4(void);
 extern int __get_user_8(void);
-extern int __get_user_nocheck_1(void);
-extern int __get_user_nocheck_2(void);
-extern int __get_user_nocheck_4(void);
-extern int __get_user_nocheck_8(void);
 extern int __get_user_bad(void);
 
 #define __uaccess_begin() stac()
@@ -56,10 +52,9 @@ extern int __get_user_bad(void);
 	__builtin_choose_expr(sizeof(x)<=sizeof(type),(unsigned type)0,not)
 
 /*
- * This is used for both get_user() and __get_user() to expand to
- * the proper special function call that has odd calling conventions
- * due to returning both a value and an error, and that depends on
- * the size of the pointer passed in.
+ * This is used by get_user() to expand to the proper special function
+ * call that has odd calling conventions due to returning both a value
+ * and an error, and that depends on the size of the pointer passed in.
  *
  * Careful: we have to cast the result to the type of the pointer
  * for sign reasons.
@@ -107,29 +102,6 @@ extern int __get_user_bad(void);
  */
 #define get_user(x,ptr) ({ might_fault(); do_get_user_call(get_user,x,ptr); })
 
-/**
- * __get_user - Get a simple variable from user space, with less checking.
- * @x:   Variable to store result.
- * @ptr: Source address, in user space.
- *
- * Context: User context only. This function may sleep if pagefaults are
- *          enabled.
- *
- * This macro copies a single simple variable from user space to kernel
- * space.  It supports simple types like char and int, but not larger
- * data types like structures or arrays.
- *
- * @ptr must have pointer-to-simple-variable type, and the result of
- * dereferencing @ptr must be assignable to @x without a cast.
- *
- * Caller must check the pointer with access_ok() before calling this
- * function.
- *
- * Return: zero on success, or -EFAULT on error.
- * On error, the variable @x is set to zero.
- */
-#define __get_user(x,ptr) do_get_user_call(get_user_nocheck,x,ptr)
-
 
 #ifdef CONFIG_X86_32
 #define __put_user_goto_u64(x, addr, label)			\
@@ -156,10 +128,6 @@ extern void __put_user_1(void);
 extern void __put_user_2(void);
 extern void __put_user_4(void);
 extern void __put_user_8(void);
-extern void __put_user_nocheck_1(void);
-extern void __put_user_nocheck_2(void);
-extern void __put_user_nocheck_4(void);
-extern void __put_user_nocheck_8(void);
 
 /*
  * ptr must be evaluated and assigned to the temporary __ptr_pu before
@@ -207,28 +175,6 @@ extern void __put_user_nocheck_8(void);
  */
 #define put_user(x, ptr) ({ might_fault(); do_put_user_call(put_user,x,ptr); })
 
-/**
- * __put_user - Write a simple value into user space, with less checking.
- * @x:   Value to copy to user space.
- * @ptr: Destination address, in user space.
- *
- * Context: User context only. This function may sleep if pagefaults are
- *          enabled.
- *
- * This macro copies a single simple value from kernel space to user
- * space.  It supports simple types like char and int, but not larger
- * data types like structures or arrays.
- *
- * @ptr must have pointer-to-simple-variable type, and @x must be assignable
- * to the result of dereferencing @ptr.
- *
- * Caller must check the pointer with access_ok() before calling this
- * function.
- *
- * Return: zero on success, or -EFAULT on error.
- */
-#define __put_user(x, ptr) do_put_user_call(put_user_nocheck,x,ptr)
-
 #define __put_user_size(x, ptr, size, label)				\
 do {									\
 	__typeof__(*(ptr)) __x = (x); /* eval x once */			\
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index 9d5654b8a72a..7c79eca08b0a 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- * __get_user functions.
+ * The out-of-line helpers for get_user().
  *
  * (C) Copyright 1998 Linus Torvalds
  * (C) Copyright 2005 Andi Kleen
@@ -37,8 +37,6 @@
 #include <asm/smap.h>
 #include <asm/runtime-const.h>
 
-#define ASM_BARRIER_NOSPEC ALTERNATIVE "", "lfence", X86_FEATURE_LFENCE_RDTSC
-
 .macro check_range size:req
 .if IS_ENABLED(CONFIG_X86_64)
 	RUNTIME_CONST_PTR USER_PTR_MAX, rdx
@@ -111,58 +109,6 @@ SYM_FUNC_START(__get_user_8)
 SYM_FUNC_END(__get_user_8)
 EXPORT_SYMBOL(__get_user_8)
 
-/* .. and the same for __get_user, just without the range checks */
-SYM_FUNC_START(__get_user_nocheck_1)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-	ASM_BARRIER_NOSPEC
-	UACCESS movzbl (%_ASM_AX),%edx
-	xor %eax,%eax
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__get_user_nocheck_1)
-EXPORT_SYMBOL(__get_user_nocheck_1)
-
-SYM_FUNC_START(__get_user_nocheck_2)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-	ASM_BARRIER_NOSPEC
-	UACCESS movzwl (%_ASM_AX),%edx
-	xor %eax,%eax
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__get_user_nocheck_2)
-EXPORT_SYMBOL(__get_user_nocheck_2)
-
-SYM_FUNC_START(__get_user_nocheck_4)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-	ASM_BARRIER_NOSPEC
-	UACCESS movl (%_ASM_AX),%edx
-	xor %eax,%eax
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__get_user_nocheck_4)
-EXPORT_SYMBOL(__get_user_nocheck_4)
-
-SYM_FUNC_START(__get_user_nocheck_8)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-	ASM_BARRIER_NOSPEC
-#ifdef CONFIG_X86_64
-	UACCESS movq (%_ASM_AX),%rdx
-#else
-	xor %ecx,%ecx
-	UACCESS movl (%_ASM_AX),%edx
-	UACCESS movl 4(%_ASM_AX),%ecx
-#endif
-	xor %eax,%eax
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__get_user_nocheck_8)
-EXPORT_SYMBOL(__get_user_nocheck_8)
-
-
 SYM_CODE_START_LOCAL(__get_user_handle_exception)
 	ASM_CLAC
 .Lbad_get_user:
diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S
index 46d9e9b98a61..9ad19f907485 100644
--- a/arch/x86/lib/putuser.S
+++ b/arch/x86/lib/putuser.S
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- * __put_user functions.
+ * The out-of-line helpers for put_user().
  *
  * (C) Copyright 2005 Linus Torvalds
  * (C) Copyright 2005 Andi Kleen
@@ -56,65 +56,35 @@ SYM_FUNC_START(__put_user_1)
 SYM_FUNC_END(__put_user_1)
 EXPORT_SYMBOL(__put_user_1)
 
-SYM_FUNC_START(__put_user_nocheck_1)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-2:	movb %al,(%_ASM_CX)
-	xor %ecx,%ecx
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__put_user_nocheck_1)
-EXPORT_SYMBOL(__put_user_nocheck_1)
-
 SYM_FUNC_START(__put_user_2)
 	ANNOTATE_NOENDBR
 	check_range size=2
 	ASM_STAC
-3:	movw %ax,(%_ASM_CX)
+2:	movw %ax,(%_ASM_CX)
 	xor %ecx,%ecx
 	ASM_CLAC
 	RET
 SYM_FUNC_END(__put_user_2)
 EXPORT_SYMBOL(__put_user_2)
 
-SYM_FUNC_START(__put_user_nocheck_2)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-4:	movw %ax,(%_ASM_CX)
-	xor %ecx,%ecx
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__put_user_nocheck_2)
-EXPORT_SYMBOL(__put_user_nocheck_2)
-
 SYM_FUNC_START(__put_user_4)
 	ANNOTATE_NOENDBR
 	check_range size=4
 	ASM_STAC
-5:	movl %eax,(%_ASM_CX)
+3:	movl %eax,(%_ASM_CX)
 	xor %ecx,%ecx
 	ASM_CLAC
 	RET
 SYM_FUNC_END(__put_user_4)
 EXPORT_SYMBOL(__put_user_4)
 
-SYM_FUNC_START(__put_user_nocheck_4)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-6:	movl %eax,(%_ASM_CX)
-	xor %ecx,%ecx
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__put_user_nocheck_4)
-EXPORT_SYMBOL(__put_user_nocheck_4)
-
 SYM_FUNC_START(__put_user_8)
 	ANNOTATE_NOENDBR
 	check_range size=8
 	ASM_STAC
-7:	mov %_ASM_AX,(%_ASM_CX)
+4:	mov %_ASM_AX,(%_ASM_CX)
 #ifdef CONFIG_X86_32
-8:	movl %edx,4(%_ASM_CX)
+5:	movl %edx,4(%_ASM_CX)
 #endif
 	xor %ecx,%ecx
 	ASM_CLAC
@@ -122,19 +92,6 @@ SYM_FUNC_START(__put_user_8)
 SYM_FUNC_END(__put_user_8)
 EXPORT_SYMBOL(__put_user_8)
 
-SYM_FUNC_START(__put_user_nocheck_8)
-	ANNOTATE_NOENDBR
-	ASM_STAC
-9:	mov %_ASM_AX,(%_ASM_CX)
-#ifdef CONFIG_X86_32
-10:	movl %edx,4(%_ASM_CX)
-#endif
-	xor %ecx,%ecx
-	ASM_CLAC
-	RET
-SYM_FUNC_END(__put_user_nocheck_8)
-EXPORT_SYMBOL(__put_user_nocheck_8)
-
 SYM_CODE_START_LOCAL(__put_user_handle_exception)
 	ASM_CLAC
 .Lbad_put_user:
@@ -146,11 +103,6 @@ SYM_CODE_END(__put_user_handle_exception)
 	_ASM_EXTABLE_UA(2b, __put_user_handle_exception)
 	_ASM_EXTABLE_UA(3b, __put_user_handle_exception)
 	_ASM_EXTABLE_UA(4b, __put_user_handle_exception)
-	_ASM_EXTABLE_UA(5b, __put_user_handle_exception)
-	_ASM_EXTABLE_UA(6b, __put_user_handle_exception)
-	_ASM_EXTABLE_UA(7b, __put_user_handle_exception)
-	_ASM_EXTABLE_UA(9b, __put_user_handle_exception)
 #ifdef CONFIG_X86_32
-	_ASM_EXTABLE_UA(8b, __put_user_handle_exception)
-	_ASM_EXTABLE_UA(10b, __put_user_handle_exception)
+	_ASM_EXTABLE_UA(5b, __put_user_handle_exception)
 #endif