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[217.178.19.87]) by smtp.gmail.com with ESMTPSA id p6sm11481026pjh.24.2021.06.19.04.35.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 19 Jun 2021 04:35:43 -0700 (PDT) Subject: [PATCH 2/5] riscv: __asm_to/copy_from_user: Adding byte copy first To: Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org References: <5a5c07ac-8c11-79d3-46a3-a255d4148f76@gmail.com> From: Akira Tsukamoto Message-ID: <98088fde-cdb2-6410-8d11-7c8ca984d3c3@gmail.com> Date: Sat, 19 Jun 2021 20:35:39 +0900 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <5a5c07ac-8c11-79d3-46a3-a255d4148f76@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Typical load and store loop. It is used for mainly copying the remainder in one byte at a time. Signed-off-by: Akira Tsukamoto --- arch/riscv/lib/uaccess.S | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S index da9536e1e9cb..be1810077f9a 100644 --- a/arch/riscv/lib/uaccess.S +++ b/arch/riscv/lib/uaccess.S @@ -19,9 +19,39 @@ ENTRY(__asm_copy_from_user) li t6, SR_SUM csrs CSR_STATUS, t6 + /* Save for return value */ + mv t5, a2 + + /* + * Register allocation for code below: + * a0 - start of uncopied dst + * a1 - start of uncopied src + * a2 - size + * t0 - end of uncopied dst + */ + add t0, a0, a2 + bgtu a0, t0, 5f + +.Lbyte_copy_tail: + /* + * Byte copy anything left. + * + * a0 - start of remaining dst + * a1 - start of remaining src + * t0 - end of remaining dst + */ + bgeu a0, t0, 5f +4: + fixup lb a5, 0(a1), 10f + addi a1, a1, 1 /* src */ + fixup sb a5, 0(a0), 10f + addi a0, a0, 1 /* dst */ + bltu a0, t0, 4b /* t0 - end of dst */ + +5: /* Disable access to user memory */ csrc CSR_STATUS, t6 - li a0, 0 + li a0, 0 ret ENDPROC(__asm_copy_to_user) ENDPROC(__asm_copy_from_user) @@ -77,7 +107,7 @@ EXPORT_SYMBOL(__clear_user) 10: /* Disable access to user memory */ csrs CSR_STATUS, t6 - mv a0, a2 + mv a0, t5 ret 11: csrs CSR_STATUS, t6 -- 2.17.1