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Date: Thu, 17 Jun 2021 03:25:08 +0200
From: Matteo Croce <mcroce@...ux.microsoft.com>
To: linux-riscv@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Atish Patra <atish.patra@....com>,
Emil Renner Berthing <kernel@...il.dk>,
Akira Tsukamoto <akira.tsukamoto@...il.com>,
Drew Fustini <drew@...gleboard.org>,
Bin Meng <bmeng.cn@...il.com>,
David Laight <David.Laight@...lab.com>,
Guo Ren <guoren@...nel.org>
Subject: [PATCH v2 2/3] riscv: optimized memmove
From: Matteo Croce <mcroce@...rosoft.com>
When the destination buffer is before the source one, or when the
buffers doesn't overlap, it's safe to use memcpy() instead, which is
optimized to use the bigger data size possible.
Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
---
arch/riscv/include/asm/string.h | 6 ++--
arch/riscv/kernel/riscv_ksyms.c | 2 --
arch/riscv/lib/Makefile | 1 -
arch/riscv/lib/memmove.S | 64 ---------------------------------
arch/riscv/lib/string.c | 26 ++++++++++++++
5 files changed, 29 insertions(+), 70 deletions(-)
delete mode 100644 arch/riscv/lib/memmove.S
diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
index 6b5d6fc3eab4..25d9b9078569 100644
--- a/arch/riscv/include/asm/string.h
+++ b/arch/riscv/include/asm/string.h
@@ -17,11 +17,11 @@ extern asmlinkage void *__memset(void *, int, size_t);
#define __HAVE_ARCH_MEMCPY
extern void *memcpy(void *dest, const void *src, size_t count);
extern void *__memcpy(void *dest, const void *src, size_t count);
+#define __HAVE_ARCH_MEMMOVE
+extern void *memmove(void *dest, const void *src, size_t count);
+extern void *__memmove(void *dest, const void *src, size_t count);
#endif
-#define __HAVE_ARCH_MEMMOVE
-extern asmlinkage void *memmove(void *, const void *, size_t);
-extern asmlinkage void *__memmove(void *, const void *, size_t);
/* For those files which don't want to check by kasan. */
#if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__)
#define memcpy(dst, src, len) __memcpy(dst, src, len)
diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c
index 3f6d512a5b97..361565c4db7e 100644
--- a/arch/riscv/kernel/riscv_ksyms.c
+++ b/arch/riscv/kernel/riscv_ksyms.c
@@ -10,6 +10,4 @@
* Assembly functions that may be used (directly or indirectly) by modules
*/
EXPORT_SYMBOL(memset);
-EXPORT_SYMBOL(memmove);
EXPORT_SYMBOL(__memset);
-EXPORT_SYMBOL(__memmove);
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 2ffe85d4baee..484f5ff7b508 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -1,7 +1,6 @@
# SPDX-License-Identifier: GPL-2.0-only
lib-y += delay.o
lib-y += memset.o
-lib-y += memmove.o
lib-$(CONFIG_MMU) += uaccess.o
lib-$(CONFIG_64BIT) += tishift.o
lib-$(CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE) += string.o
diff --git a/arch/riscv/lib/memmove.S b/arch/riscv/lib/memmove.S
deleted file mode 100644
index 07d1d2152ba5..000000000000
--- a/arch/riscv/lib/memmove.S
+++ /dev/null
@@ -1,64 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-
-#include <linux/linkage.h>
-#include <asm/asm.h>
-
-ENTRY(__memmove)
-WEAK(memmove)
- move t0, a0
- move t1, a1
-
- beq a0, a1, exit_memcpy
- beqz a2, exit_memcpy
- srli t2, a2, 0x2
-
- slt t3, a0, a1
- beqz t3, do_reverse
-
- andi a2, a2, 0x3
- li t4, 1
- beqz t2, byte_copy
-
-word_copy:
- lw t3, 0(a1)
- addi t2, t2, -1
- addi a1, a1, 4
- sw t3, 0(a0)
- addi a0, a0, 4
- bnez t2, word_copy
- beqz a2, exit_memcpy
- j byte_copy
-
-do_reverse:
- add a0, a0, a2
- add a1, a1, a2
- andi a2, a2, 0x3
- li t4, -1
- beqz t2, reverse_byte_copy
-
-reverse_word_copy:
- addi a1, a1, -4
- addi t2, t2, -1
- lw t3, 0(a1)
- addi a0, a0, -4
- sw t3, 0(a0)
- bnez t2, reverse_word_copy
- beqz a2, exit_memcpy
-
-reverse_byte_copy:
- addi a0, a0, -1
- addi a1, a1, -1
-
-byte_copy:
- lb t3, 0(a1)
- addi a2, a2, -1
- sb t3, 0(a0)
- add a1, a1, t4
- add a0, a0, t4
- bnez a2, byte_copy
-
-exit_memcpy:
- move a0, t0
- move a1, t1
- ret
-END(__memmove)
diff --git a/arch/riscv/lib/string.c b/arch/riscv/lib/string.c
index 694352d21c21..c932401e365b 100644
--- a/arch/riscv/lib/string.c
+++ b/arch/riscv/lib/string.c
@@ -92,3 +92,29 @@ void *__memcpy(void *dest, const void *src, size_t count)
return memcpy(dest, src, count);
}
EXPORT_SYMBOL(__memcpy);
+
+/*
+ * Simply check if the buffer overlaps an call memcpy() in case,
+ * otherwise do a simple one byte at time backward copy.
+ */
+void __weak *memmove(void *dest, const void *src, size_t count)
+{
+ if (dest < src || src + count <= dest)
+ return memcpy(dest, src, count);
+
+ if (dest > src) {
+ const char *s = src + count;
+ char *tmp = dest + count;
+
+ while (count--)
+ *--tmp = *--s;
+ }
+ return dest;
+}
+EXPORT_SYMBOL(memmove);
+
+void *__memmove(void *dest, const void *src, size_t count)
+{
+ return memmove(dest, src, count);
+}
+EXPORT_SYMBOL(__memmove);
--
2.31.1
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