linux-kernel - [PATCH 2/8] asm-generic: improve the nommu {get,put}

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Message-Id: <20200907055825.1917151-3-hch@lst.de>
Date:   Mon,  7 Sep 2020 07:58:19 +0200
From:   Christoph Hellwig <hch@....de>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Arnd Bergmann <arnd@...db.de>,
        Alexander Viro <viro@...iv.linux.org.uk>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org
Subject: [PATCH 2/8] asm-generic: improve the nommu {get,put}_user handling

Instead of reusing raw_{copy,to}_from_user implement separate handlers
using {get,put}_unaligned.  This ensures unaligned access is handled
correctly, and avoid the need for the small constant size optimization
in raw_{copy,to}_from_user.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 include/asm-generic/uaccess.h | 91 ++++++++++++++++++++---------------
 1 file changed, 51 insertions(+), 40 deletions(-)

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index ba68ee4dabfaa7..6de5f524e9e631 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -10,28 +10,60 @@
 #include <linux/string.h>
 
 #ifdef CONFIG_UACCESS_MEMCPY
-static inline __must_check unsigned long
-raw_copy_from_user(void *to, const void __user * from, unsigned long n)
+#include <asm/unaligned.h>
+
+static inline int __get_user_fn(size_t size, const void __user *from, void *to)
 {
-	if (__builtin_constant_p(n)) {
-		switch(n) {
-		case 1:
-			*(u8 *)to = *(u8 __force *)from;
-			return 0;
-		case 2:
-			*(u16 *)to = *(u16 __force *)from;
-			return 0;
-		case 4:
-			*(u32 *)to = *(u32 __force *)from;
-			return 0;
-#ifdef CONFIG_64BIT
-		case 8:
-			*(u64 *)to = *(u64 __force *)from;
-			return 0;
-#endif
-		}
+	BUILD_BUG_ON(!__builtin_constant_p(size));
+
+	switch (size) {
+	case 1:
+		*(u8 *)to = get_unaligned((u8 __force *)from);
+		return 0;
+	case 2:
+		*(u16 *)to = get_unaligned((u16 __force *)from);
+		return 0;
+	case 4:
+		*(u32 *)to = get_unaligned((u32 __force *)from);
+		return 0;
+	case 8:
+		*(u64 *)to = get_unaligned((u64 __force *)from);
+		return 0;
+	default:
+		BUILD_BUG();
+		return 0;
+	}
+
+}
+#define __get_user_fn(sz, u, k)	__get_user_fn(sz, u, k)
+
+static inline int __put_user_fn(size_t size, void __user *to, void *from)
+{
+	BUILD_BUG_ON(!__builtin_constant_p(size));
+
+	switch (size) {
+	case 1:
+		put_unaligned(*(u8 *)from, (u8 __force *)to);
+		return 0;
+	case 2:
+		put_unaligned(*(u16 *)from, (u16 __force *)to);
+		return 0;
+	case 4:
+		put_unaligned(*(u32 *)from, (u32 __force *)to);
+		return 0;
+	case 8:
+		put_unaligned(*(u64 *)from, (u64 __force *)to);
+		return 0;
+	default:
+		BUILD_BUG();
+		return 0;
 	}
+}
+#define __put_user_fn(sz, u, k)	__put_user_fn(sz, u, k)
 
+static inline __must_check unsigned long
+raw_copy_from_user(void *to, const void __user * from, unsigned long n)
+{
 	memcpy(to, (const void __force *)from, n);
 	return 0;
 }
@@ -39,27 +71,6 @@ raw_copy_from_user(void *to, const void __user * from, unsigned long n)
 static inline __must_check unsigned long
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	if (__builtin_constant_p(n)) {
-		switch(n) {
-		case 1:
-			*(u8 __force *)to = *(u8 *)from;
-			return 0;
-		case 2:
-			*(u16 __force *)to = *(u16 *)from;
-			return 0;
-		case 4:
-			*(u32 __force *)to = *(u32 *)from;
-			return 0;
-#ifdef CONFIG_64BIT
-		case 8:
-			*(u64 __force *)to = *(u64 *)from;
-			return 0;
-#endif
-		default:
-			break;
-		}
-	}
-
 	memcpy((void __force *)to, from, n);
 	return 0;
 }
-- 
2.28.0