arm64: uaccess: Remove uaccess_*_not_uao asm macros

It is safer and simpler to drop the uaccess assembly macros in favour of
inline C functions. Although this bloats the Image size slightly, it
aligns our user copy routines with '{get,put}_user()' and generally
makes the code a lot easier to reason about.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com>
[will: tweaked commit message and changed temporary variable names]
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/asm-uaccess.h

@@ -58,23 +58,6 @@ alternative_else_nop_endif
 	.endm
 #endif
 
-/*
- * These macros are no-ops when UAO is present.
- */
-	.macro	uaccess_disable_not_uao, tmp1, tmp2
-	uaccess_ttbr0_disable \tmp1, \tmp2
-alternative_if ARM64_ALT_PAN_NOT_UAO
-	SET_PSTATE_PAN(1)
-alternative_else_nop_endif
-	.endm
-
-	.macro	uaccess_enable_not_uao, tmp1, tmp2, tmp3
-	uaccess_ttbr0_enable \tmp1, \tmp2, \tmp3
-alternative_if ARM64_ALT_PAN_NOT_UAO
-	SET_PSTATE_PAN(0)
-alternative_else_nop_endif
-	.endm
-
 /*
  * Remove the address tag from a virtual address, if present.
  */

arch/arm64/include/asm/uaccess.h

@@ -378,20 +378,34 @@ do {									\
 extern unsigned long __must_check __arch_copy_from_user(void *to, const void __user *from, unsigned long n);
 #define raw_copy_from_user(to, from, n)					\
 ({									\
-	__arch_copy_from_user((to), __uaccess_mask_ptr(from), (n));	\
+	unsigned long __acfu_ret;					\
+	uaccess_enable_not_uao();					\
+	__acfu_ret = __arch_copy_from_user((to),			\
+				      __uaccess_mask_ptr(from), (n));	\
+	uaccess_disable_not_uao();					\
+	__acfu_ret;							\
 })
 
 extern unsigned long __must_check __arch_copy_to_user(void __user *to, const void *from, unsigned long n);
 #define raw_copy_to_user(to, from, n)					\
 ({									\
-	__arch_copy_to_user(__uaccess_mask_ptr(to), (from), (n));	\
+	unsigned long __actu_ret;					\
+	uaccess_enable_not_uao();					\
+	__actu_ret = __arch_copy_to_user(__uaccess_mask_ptr(to),	\
+				    (from), (n));			\
+	uaccess_disable_not_uao();					\
+	__actu_ret;							\
 })
 
 extern unsigned long __must_check __arch_copy_in_user(void __user *to, const void __user *from, unsigned long n);
 #define raw_copy_in_user(to, from, n)					\
 ({									\
-	__arch_copy_in_user(__uaccess_mask_ptr(to),			\
-			    __uaccess_mask_ptr(from), (n));		\
+	unsigned long __aciu_ret;					\
+	uaccess_enable_not_uao();					\
+	__aciu_ret = __arch_copy_in_user(__uaccess_mask_ptr(to),	\
+				    __uaccess_mask_ptr(from), (n));	\
+	uaccess_disable_not_uao();					\
+	__aciu_ret;							\
 })
 
 #define INLINE_COPY_TO_USER
@@ -400,8 +414,11 @@ extern unsigned long __must_check __arch_copy_in_user(void __user *to, const voi
 extern unsigned long __must_check __arch_clear_user(void __user *to, unsigned long n);
 static inline unsigned long __must_check __clear_user(void __user *to, unsigned long n)
 {
-	if (access_ok(to, n))
+	if (access_ok(to, n)) {
+		uaccess_enable_not_uao();
 		n = __arch_clear_user(__uaccess_mask_ptr(to), n);
+		uaccess_disable_not_uao();
+	}
 	return n;
 }
 #define clear_user	__clear_user

arch/arm64/lib/clear_user.S

@@ -20,7 +20,6 @@
  * Alignment fixed up by hardware.
  */
 ENTRY(__arch_clear_user)
-	uaccess_enable_not_uao x2, x3, x4
 	mov	x2, x1			// save the size for fixup return
 	subs	x1, x1, #8
 	b.mi	2f
@@ -40,7 +39,6 @@ uao_user_alternative 9f, strh, sttrh, wzr, x0, 2
 	b.mi	5f
 uao_user_alternative 9f, strb, sttrb, wzr, x0, 0
 5:	mov	x0, #0
-	uaccess_disable_not_uao x2, x3
 	ret
 ENDPROC(__arch_clear_user)
 EXPORT_SYMBOL(__arch_clear_user)
@@ -48,6 +46,5 @@ EXPORT_SYMBOL(__arch_clear_user)
 	.section .fixup,"ax"
 	.align	2
 9:	mov	x0, x2			// return the original size
-	uaccess_disable_not_uao x2, x3
 	ret
 	.previous

arch/arm64/lib/copy_from_user.S

@@ -54,10 +54,8 @@
 
 end	.req	x5
 ENTRY(__arch_copy_from_user)
-	uaccess_enable_not_uao x3, x4, x5
 	add	end, x0, x2
 #include "copy_template.S"
-	uaccess_disable_not_uao x3, x4
 	mov	x0, #0				// Nothing to copy
 	ret
 ENDPROC(__arch_copy_from_user)
@@ -66,6 +64,5 @@ EXPORT_SYMBOL(__arch_copy_from_user)
 	.section .fixup,"ax"
 	.align	2
 9998:	sub	x0, end, dst			// bytes not copied
-	uaccess_disable_not_uao x3, x4
 	ret
 	.previous

arch/arm64/lib/copy_in_user.S

@@ -56,10 +56,8 @@
 end	.req	x5
 
 ENTRY(__arch_copy_in_user)
-	uaccess_enable_not_uao x3, x4, x5
 	add	end, x0, x2
 #include "copy_template.S"
-	uaccess_disable_not_uao x3, x4
 	mov	x0, #0
 	ret
 ENDPROC(__arch_copy_in_user)
@@ -68,6 +66,5 @@ EXPORT_SYMBOL(__arch_copy_in_user)
 	.section .fixup,"ax"
 	.align	2
 9998:	sub	x0, end, dst			// bytes not copied
-	uaccess_disable_not_uao x3, x4
 	ret
 	.previous

arch/arm64/lib/copy_to_user.S

@@ -53,10 +53,8 @@
 
 end	.req	x5
 ENTRY(__arch_copy_to_user)
-	uaccess_enable_not_uao x3, x4, x5
 	add	end, x0, x2
 #include "copy_template.S"
-	uaccess_disable_not_uao x3, x4
 	mov	x0, #0
 	ret
 ENDPROC(__arch_copy_to_user)
@@ -65,6 +63,5 @@ EXPORT_SYMBOL(__arch_copy_to_user)
 	.section .fixup,"ax"
 	.align	2
 9998:	sub	x0, end, dst			// bytes not copied
-	uaccess_disable_not_uao x3, x4
 	ret
 	.previous

arch/arm64/lib/uaccess_flushcache.c

@@ -28,7 +28,11 @@ void memcpy_page_flushcache(char *to, struct page *page, size_t offset,
 unsigned long __copy_user_flushcache(void *to, const void __user *from,
 				     unsigned long n)
 {
-	unsigned long rc = __arch_copy_from_user(to, from, n);
+	unsigned long rc;
+
+	uaccess_enable_not_uao();
+	rc = __arch_copy_from_user(to, from, n);
+	uaccess_disable_not_uao();
 
 	/* See above */
 	__clean_dcache_area_pop(to, n - rc);