riscv: optimized memmove

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 a bigger data size possible.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>

diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
index 23fdcbf..0212046 100644 (file)
--- a/arch/riscv/include/asm/string.h
+++ b/arch/riscv/include/asm/string.h
@@ -16,10 +16,10 @@ 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 asmlinkage void *memmove(void *, const void *, size_t);
-extern asmlinkage void *__memmove(void *, const void *, size_t);
+extern void *memmove(void *dest, const void *src, size_t count);
+extern void *__memmove(void *dest, const void *src, size_t count);
+
 /* 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 3f6d512..361565c 100644 (file)
--- 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 023d78f..9166b61 100644 (file)
--- 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-y                  += string.o

diff --git a/arch/riscv/lib/memmove.S b/arch/riscv/lib/memmove.S
deleted file mode 100644 (file)
index e0609e1..0000000
--- a/arch/riscv/lib/memmove.S
+++ /dev/null
@@ -1,316 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Copyright (C) 2022 Michael T. Kloos <michael@michaelkloos.com>
- */
-
-#include <linux/linkage.h>
-#include <asm/asm.h>
-
-SYM_FUNC_START(__memmove)
-SYM_FUNC_START_WEAK(memmove)
-       /*
-        * Returns
-        *   a0 - dest
-        *
-        * Parameters
-        *   a0 - Inclusive first byte of dest
-        *   a1 - Inclusive first byte of src
-        *   a2 - Length of copy n
-        *
-        * Because the return matches the parameter register a0,
-        * we will not clobber or modify that register.
-        *
-        * Note: This currently only works on little-endian.
-        * To port to big-endian, reverse the direction of shifts
-        * in the 2 misaligned fixup copy loops.
-        */
-
-       /* Return if nothing to do */
-       beq a0, a1, return_from_memmove
-       beqz a2, return_from_memmove
-
-       /*
-        * Register Uses
-        *      Forward Copy: a1 - Index counter of src
-        *      Reverse Copy: a4 - Index counter of src
-        *      Forward Copy: t3 - Index counter of dest
-        *      Reverse Copy: t4 - Index counter of dest
-        *   Both Copy Modes: t5 - Inclusive first multibyte/aligned of dest
-        *   Both Copy Modes: t6 - Non-Inclusive last multibyte/aligned of dest
-        *   Both Copy Modes: t0 - Link / Temporary for load-store
-        *   Both Copy Modes: t1 - Temporary for load-store
-        *   Both Copy Modes: t2 - Temporary for load-store
-        *   Both Copy Modes: a5 - dest to src alignment offset
-        *   Both Copy Modes: a6 - Shift ammount
-        *   Both Copy Modes: a7 - Inverse Shift ammount
-        *   Both Copy Modes: a2 - Alternate breakpoint for unrolled loops
-        */
-
-       /*
-        * Solve for some register values now.
-        * Byte copy does not need t5 or t6.
-        */
-       mv   t3, a0
-       add  t4, a0, a2
-       add  a4, a1, a2
-
-       /*
-        * Byte copy if copying less than (2 * SZREG) bytes. This can
-        * cause problems with the bulk copy implementation and is
-        * small enough not to bother.
-        */
-       andi t0, a2, -(2 * SZREG)
-       beqz t0, byte_copy
-
-       /*
-        * Now solve for t5 and t6.
-        */
-       andi t5, t3, -SZREG
-       andi t6, t4, -SZREG
-       /*
-        * If dest(Register t3) rounded down to the nearest naturally
-        * aligned SZREG address, does not equal dest, then add SZREG
-        * to find the low-bound of SZREG alignment in the dest memory
-        * region.  Note that this could overshoot the dest memory
-        * region if n is less than SZREG.  This is one reason why
-        * we always byte copy if n is less than SZREG.
-        * Otherwise, dest is already naturally aligned to SZREG.
-        */
-       beq  t5, t3, 1f
-               addi t5, t5, SZREG
-       1:
-
-       /*
-        * If the dest and src are co-aligned to SZREG, then there is
-        * no need for the full rigmarole of a full misaligned fixup copy.
-        * Instead, do a simpler co-aligned copy.
-        */
-       xor  t0, a0, a1
-       andi t1, t0, (SZREG - 1)
-       beqz t1, coaligned_copy
-       /* Fall through to misaligned fixup copy */
-
-misaligned_fixup_copy:
-       bltu a1, a0, misaligned_fixup_copy_reverse
-
-misaligned_fixup_copy_forward:
-       jal  t0, byte_copy_until_aligned_forward
-
-       andi a5, a1, (SZREG - 1) /* Find the alignment offset of src (a1) */
-       slli a6, a5, 3 /* Multiply by 8 to convert that to bits to shift */
-       sub  a5, a1, t3 /* Find the difference between src and dest */
-       andi a1, a1, -SZREG /* Align the src pointer */
-       addi a2, t6, SZREG /* The other breakpoint for the unrolled loop*/
-
-       /*
-        * Compute The Inverse Shift
-        * a7 = XLEN - a6 = XLEN + -a6
-        * 2s complement negation to find the negative: -a6 = ~a6 + 1
-        * Add that to XLEN.  XLEN = SZREG * 8.
-        */
-       not  a7, a6
-       addi a7, a7, (SZREG * 8 + 1)
-
-       /*
-        * Fix Misalignment Copy Loop - Forward
-        * load_val0 = load_ptr[0];
-        * do {
-        *      load_val1 = load_ptr[1];
-        *      store_ptr += 2;
-        *      store_ptr[0 - 2] = (load_val0 >> {a6}) | (load_val1 << {a7});
-        *
-        *      if (store_ptr == {a2})
-        *              break;
-        *
-        *      load_val0 = load_ptr[2];
-        *      load_ptr += 2;
-        *      store_ptr[1 - 2] = (load_val1 >> {a6}) | (load_val0 << {a7});
-        *
-        * } while (store_ptr != store_ptr_end);
-        * store_ptr = store_ptr_end;
-        */
-
-       REG_L t0, (0 * SZREG)(a1)
-       1:
-       REG_L t1, (1 * SZREG)(a1)
-       addi  t3, t3, (2 * SZREG)
-       srl   t0, t0, a6
-       sll   t2, t1, a7
-       or    t2, t0, t2
-       REG_S t2, ((0 * SZREG) - (2 * SZREG))(t3)
-
-       beq   t3, a2, 2f
-
-       REG_L t0, (2 * SZREG)(a1)
-       addi  a1, a1, (2 * SZREG)
-       srl   t1, t1, a6
-       sll   t2, t0, a7
-       or    t2, t1, t2
-       REG_S t2, ((1 * SZREG) - (2 * SZREG))(t3)
-
-       bne   t3, t6, 1b
-       2:
-       mv    t3, t6 /* Fix the dest pointer in case the loop was broken */
-
-       add  a1, t3, a5 /* Restore the src pointer */
-       j byte_copy_forward /* Copy any remaining bytes */
-
-misaligned_fixup_copy_reverse:
-       jal  t0, byte_copy_until_aligned_reverse
-
-       andi a5, a4, (SZREG - 1) /* Find the alignment offset of src (a4) */
-       slli a6, a5, 3 /* Multiply by 8 to convert that to bits to shift */
-       sub  a5, a4, t4 /* Find the difference between src and dest */
-       andi a4, a4, -SZREG /* Align the src pointer */
-       addi a2, t5, -SZREG /* The other breakpoint for the unrolled loop*/
-
-       /*
-        * Compute The Inverse Shift
-        * a7 = XLEN - a6 = XLEN + -a6
-        * 2s complement negation to find the negative: -a6 = ~a6 + 1
-        * Add that to XLEN.  XLEN = SZREG * 8.
-        */
-       not  a7, a6
-       addi a7, a7, (SZREG * 8 + 1)
-
-       /*
-        * Fix Misalignment Copy Loop - Reverse
-        * load_val1 = load_ptr[0];
-        * do {
-        *      load_val0 = load_ptr[-1];
-        *      store_ptr -= 2;
-        *      store_ptr[1] = (load_val0 >> {a6}) | (load_val1 << {a7});
-        *
-        *      if (store_ptr == {a2})
-        *              break;
-        *
-        *      load_val1 = load_ptr[-2];
-        *      load_ptr -= 2;
-        *      store_ptr[0] = (load_val1 >> {a6}) | (load_val0 << {a7});
-        *
-        * } while (store_ptr != store_ptr_end);
-        * store_ptr = store_ptr_end;
-        */
-
-       REG_L t1, ( 0 * SZREG)(a4)
-       1:
-       REG_L t0, (-1 * SZREG)(a4)
-       addi  t4, t4, (-2 * SZREG)
-       sll   t1, t1, a7
-       srl   t2, t0, a6
-       or    t2, t1, t2
-       REG_S t2, ( 1 * SZREG)(t4)
-
-       beq   t4, a2, 2f
-
-       REG_L t1, (-2 * SZREG)(a4)
-       addi  a4, a4, (-2 * SZREG)
-       sll   t0, t0, a7
-       srl   t2, t1, a6
-       or    t2, t0, t2
-       REG_S t2, ( 0 * SZREG)(t4)
-
-       bne   t4, t5, 1b
-       2:
-       mv    t4, t5 /* Fix the dest pointer in case the loop was broken */
-
-       add  a4, t4, a5 /* Restore the src pointer */
-       j byte_copy_reverse /* Copy any remaining bytes */
-
-/*
- * Simple copy loops for SZREG co-aligned memory locations.
- * These also make calls to do byte copies for any unaligned
- * data at their terminations.
- */
-coaligned_copy:
-       bltu a1, a0, coaligned_copy_reverse
-
-coaligned_copy_forward:
-       jal t0, byte_copy_until_aligned_forward
-
-       1:
-       REG_L t1, ( 0 * SZREG)(a1)
-       addi  a1, a1, SZREG
-       addi  t3, t3, SZREG
-       REG_S t1, (-1 * SZREG)(t3)
-       bne   t3, t6, 1b
-
-       j byte_copy_forward /* Copy any remaining bytes */
-
-coaligned_copy_reverse:
-       jal t0, byte_copy_until_aligned_reverse
-
-       1:
-       REG_L t1, (-1 * SZREG)(a4)
-       addi  a4, a4, -SZREG
-       addi  t4, t4, -SZREG
-       REG_S t1, ( 0 * SZREG)(t4)
-       bne   t4, t5, 1b
-
-       j byte_copy_reverse /* Copy any remaining bytes */
-
-/*
- * These are basically sub-functions within the function.  They
- * are used to byte copy until the dest pointer is in alignment.
- * At which point, a bulk copy method can be used by the
- * calling code.  These work on the same registers as the bulk
- * copy loops.  Therefore, the register values can be picked
- * up from where they were left and we avoid code duplication
- * without any overhead except the call in and return jumps.
- */
-byte_copy_until_aligned_forward:
-       beq  t3, t5, 2f
-       1:
-       lb   t1,  0(a1)
-       addi a1, a1, 1
-       addi t3, t3, 1
-       sb   t1, -1(t3)
-       bne  t3, t5, 1b
-       2:
-       jalr zero, 0x0(t0) /* Return to multibyte copy loop */
-
-byte_copy_until_aligned_reverse:
-       beq  t4, t6, 2f
-       1:
-       lb   t1, -1(a4)
-       addi a4, a4, -1
-       addi t4, t4, -1
-       sb   t1,  0(t4)
-       bne  t4, t6, 1b
-       2:
-       jalr zero, 0x0(t0) /* Return to multibyte copy loop */
-
-/*
- * Simple byte copy loops.
- * These will byte copy until they reach the end of data to copy.
- * At that point, they will call to return from memmove.
- */
-byte_copy:
-       bltu a1, a0, byte_copy_reverse
-
-byte_copy_forward:
-       beq  t3, t4, 2f
-       1:
-       lb   t1,  0(a1)
-       addi a1, a1, 1
-       addi t3, t3, 1
-       sb   t1, -1(t3)
-       bne  t3, t4, 1b
-       2:
-       ret
-
-byte_copy_reverse:
-       beq  t4, t3, 2f
-       1:
-       lb   t1, -1(a4)
-       addi a4, a4, -1
-       addi t4, t4, -1
-       sb   t1,  0(t4)
-       bne  t4, t3, 1b
-       2:
-
-return_from_memmove:
-       ret
-
-SYM_FUNC_END(memmove)
-SYM_FUNC_END(__memmove)

diff --git a/arch/riscv/lib/string.c b/arch/riscv/lib/string.c
index 32509ab..bd52581 100644 (file)
--- a/arch/riscv/lib/string.c
+++ b/arch/riscv/lib/string.c
@@ -89,3 +89,26 @@ EXPORT_SYMBOL(__memcpy);
 
 void *memcpy(void *dest, const void *src, size_t count) __weak __alias(__memcpy);
 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 *__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) __weak __alias(__memmove);
+EXPORT_SYMBOL(memmove);