linux-kernel - [PATCH 7/8] riscv: implement __get_kernel_nofault and __put_user

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Date:   Fri,  4 Sep 2020 18:52:15 +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 7/8] riscv: implement __get_kernel_nofault and __put_user_nofault

Implemet the non-faulting kernel access helpers directly instead of
abusing the uaccess routines under set_fs(KERNEL_DS).

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/riscv/include/asm/uaccess.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
index b67d1c616ec348..264e52fb62b143 100644
--- a/arch/riscv/include/asm/uaccess.h
+++ b/arch/riscv/include/asm/uaccess.h
@@ -486,6 +486,26 @@ unsigned long __must_check clear_user(void __user *to, unsigned long n)
 	__ret;							\
 })
 
+#define HAVE_GET_KERNEL_NOFAULT
+
+#define __get_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	long __kr_err;							\
+									\
+	__get_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err);	\
+	if (unlikely(__kr_err))						\
+		goto err_label;						\
+} while (0)
+
+#define __put_kernel_nofault(dst, src, type, err_label)			\
+do {									\
+	long __kr_err;							\
+									\
+	__put_user_nocheck(*((type *)(dst)), (type *)(src), __kr_err);	\
+	if (unlikely(__kr_err))						\
+		goto err_label;						\
+} while (0)
+
 #else /* CONFIG_MMU */
 #include <asm-generic/uaccess.h>
 #endif /* CONFIG_MMU */
-- 
2.28.0