linux-kernel - [PATCH 2/4] riscv: __asm_copy_to-from

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Message-ID: <93a6ae3b-3271-5edb-0a1b-260ba789f3f1@gmail.com>
Date:   Tue, 20 Jul 2021 17:51:45 +0900
From:   Akira Tsukamoto <akira.tsukamoto@...il.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] riscv: __asm_copy_to-from_user: Fix: fail on RV32


Had a bug when converting bytes to bits when the cpu was rv32.

The a3 contains the number of bytes and multiple of 8
would be the bits. The LGREG is holding 2 for RV32 and 3 for
RV32, so to achieve multiple of 8 it must always be constant 3.
The 2 was mistakenly used for rv32.

Signed-off-by: Akira Tsukamoto <akira.tsukamoto@...il.com>
---
 arch/riscv/lib/uaccess.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
index 8bbeca89a93f..279876821969 100644
--- a/arch/riscv/lib/uaccess.S
+++ b/arch/riscv/lib/uaccess.S
@@ -125,7 +125,7 @@ ENTRY(__asm_copy_from_user)
 	 * t3 - prev shift
 	 * t4 - current shift
 	 */
-	slli	t3, a3, LGREG
+	slli	t3, a3, 3 /* converting bytes in a3 to bits */
 	li	a5, SZREG*8
 	sub	t4, a5, t3
 
-- 
2.17.1