linux-kernel - [RFC 2/3] ARM: uaccess: let UACCESS_GUP_KMAP

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Date:   Fri, 12 Jun 2020 15:48:10 +0530
From:   afzal mohammed <afzal.mohd.ma@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>,
        Arnd Bergmann <arnd@...db.de>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        Nicolas Pitre <nico@...xnic.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Subject: [RFC 2/3] ARM: uaccess: let UACCESS_GUP_KMAP_MEMCPY enabling

Turn off existing raw_copy_{from,to}_user() using
arm_copy_{from,to}_user() when CONFIG_UACCESS_GUP_KMAP_MEMCPY is
enabled.

Signed-off-by: afzal mohammed <afzal.mohd.ma@...il.com>
---
 arch/arm/include/asm/uaccess.h | 20 ++++++++++++++++++++
 arch/arm/kernel/armksyms.c     |  2 ++
 arch/arm/lib/Makefile          |  7 +++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 98c6b91be4a8a..4a16ae52d4978 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -512,6 +512,15 @@ do {									\
 extern unsigned long __must_check
 arm_copy_from_user(void *to, const void __user *from, unsigned long n);
 
+#ifdef CONFIG_UACCESS_GUP_KMAP_MEMCPY
+extern unsigned long __must_check
+gup_kmap_copy_from_user(void *to, const void __user *from, unsigned long n);
+static inline __must_check unsigned long
+raw_copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+	return gup_kmap_copy_from_user(to, from, n);
+}
+#else
 static inline unsigned long __must_check
 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
@@ -522,12 +531,22 @@ raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 	uaccess_restore(__ua_flags);
 	return n;
 }
+#endif
 
 extern unsigned long __must_check
 arm_copy_to_user(void __user *to, const void *from, unsigned long n);
 extern unsigned long __must_check
 __copy_to_user_std(void __user *to, const void *from, unsigned long n);
 
+#ifdef CONFIG_UACCESS_GUP_KMAP_MEMCPY
+extern unsigned long __must_check
+gup_kmap_copy_to_user(void __user *to, const void *from, unsigned long n);
+static inline __must_check unsigned long
+raw_copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+	return gup_kmap_copy_to_user(to, from, n);
+}
+#else
 static inline unsigned long __must_check
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
@@ -541,6 +560,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 	return arm_copy_to_user(to, from, n);
 #endif
 }
+#endif
 
 extern unsigned long __must_check
 arm_clear_user(void __user *addr, unsigned long n);
diff --git a/arch/arm/kernel/armksyms.c b/arch/arm/kernel/armksyms.c
index 98bdea51089d5..8c92fe30d1559 100644
--- a/arch/arm/kernel/armksyms.c
+++ b/arch/arm/kernel/armksyms.c
@@ -96,8 +96,10 @@ EXPORT_SYMBOL(mmiocpy);
 #ifdef CONFIG_MMU
 EXPORT_SYMBOL(copy_page);
 
+#ifndef CONFIG_UACCESS_GUP_KMAP_MEMCPY
 EXPORT_SYMBOL(arm_copy_from_user);
 EXPORT_SYMBOL(arm_copy_to_user);
+#endif
 EXPORT_SYMBOL(arm_clear_user);
 
 EXPORT_SYMBOL(__get_user_1);
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 6d2ba454f25b6..1aeff2cd7b4b3 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -16,8 +16,11 @@ lib-y		:= changebit.o csumipv6.o csumpartial.o               \
 		   io-readsb.o io-writesb.o io-readsl.o io-writesl.o  \
 		   call_with_stack.o bswapsdi2.o
 
-mmu-y		:= clear_user.o copy_page.o getuser.o putuser.o       \
-		   copy_from_user.o copy_to_user.o
+mmu-y		:= clear_user.o copy_page.o getuser.o putuser.o
+
+ifndef CONFIG_UACCESS_GUP_KMAP_MEMCPY
+  mmu-y		+= copy_from_user.o copy_to_user.o
+endif
 
 ifdef CONFIG_CC_IS_CLANG
   lib-y	+= backtrace-clang.o
-- 
2.26.2