From: Akira Tsukamoto <akira.tsukamoto@gmail.com>
To: Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org
Subject: [PATCH 2/5] riscv: __asm_to/copy_from_user: Adding byte copy first
Date: Sat, 19 Jun 2021 20:35:39 +0900 [thread overview]
Message-ID: <98088fde-cdb2-6410-8d11-7c8ca984d3c3@gmail.com> (raw)
In-Reply-To: <5a5c07ac-8c11-79d3-46a3-a255d4148f76@gmail.com>
Typical load and store loop.
It is used for mainly copying the remainder in one byte at a time.
Signed-off-by: Akira Tsukamoto <akira.tsukamoto@gmail.com>
---
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
next prev parent reply other threads:[~2021-06-19 11:35 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-19 11:21 [PATCH v2 0/5] riscv: improving uaccess with logs from network bench Akira Tsukamoto
2021-06-19 11:34 ` [PATCH 1/5] riscv: __asm_to/copy_from_user: delete existing code Akira Tsukamoto
2021-06-21 11:45 ` David Laight
2021-06-21 13:55 ` Akira Tsukamoto
2021-06-19 11:35 ` Akira Tsukamoto [this message]
2021-06-19 11:36 ` [PATCH 3/5] riscv: __asm_to/copy_from_user: Copy until dst is aligned Akira Tsukamoto
2021-06-19 11:37 ` [PATCH 4/5] riscv: __asm_to/copy_from_user: Bulk copy while shifting Akira Tsukamoto
2021-06-19 11:43 ` [PATCH 5/5] riscv: __asm_to/copy_from_user: Bulk copy when both src, dst are aligned Akira Tsukamoto
2021-06-21 11:55 ` David Laight
2021-06-21 14:13 ` Akira Tsukamoto
2021-06-20 10:02 ` [PATCH v2 0/5] riscv: improving uaccess with logs from network bench Ben Dooks
2021-06-20 16:36 ` Akira Tsukamoto
2021-06-22 8:30 ` Ben Dooks
2021-06-22 12:05 ` Akira Tsukamoto
2021-06-22 17:45 ` Ben Dooks
2021-07-12 21:24 ` Ben Dooks
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