[MIPS] csum_partial and copy in parallel

Implement optimized asm version of csum_partial_copy_nocheck,
csum_partial_copy_from_user and csum_and_copy_to_user which can do
calculate and copy in parallel, based on memcpy.S.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

5 files changed, 464 insertions, 65 deletions

diff --git a/arch/mips/kernel/mips_ksyms.c b/arch/mips/kernel/mips_ksyms.c
index f44a01357ada..2ef857c3ee53 100644
--- a/arch/mips/kernel/mips_ksyms.c
+++ b/arch/mips/kernel/mips_ksyms.c
@@ -46,5 +46,7 @@ EXPORT_SYMBOL(__strnlen_user_nocheck_asm);
 EXPORT_SYMBOL(__strnlen_user_asm);
 
 EXPORT_SYMBOL(csum_partial);
+EXPORT_SYMBOL(csum_partial_copy_nocheck);
+EXPORT_SYMBOL(__csum_partial_copy_user);
 
 EXPORT_SYMBOL(invalid_pte_table);
diff --git a/arch/mips/lib/Makefile b/arch/mips/lib/Makefile
index 888b61ea12fe..989c900b8b14 100644
--- a/arch/mips/lib/Makefile
+++ b/arch/mips/lib/Makefile
@@ -2,7 +2,7 @@
 # Makefile for MIPS-specific library files..
 #
 
-lib-y   += csum_partial.o csum_partial_copy.o memcpy.o promlib.o \
+lib-y   += csum_partial.o memcpy.o promlib.o \
            strlen_user.o strncpy_user.o strnlen_user.o uncached.o
 
 obj-y   += iomap.o
diff --git a/arch/mips/lib/csum_partial.S b/arch/mips/lib/csum_partial.S
index 9db357294be1..c0a77fe038be 100644
--- a/arch/mips/lib/csum_partial.S
+++ b/arch/mips/lib/csum_partial.S
@@ -8,7 +8,9 @@
  * Copyright (C) 1998, 1999 Ralf Baechle
  * Copyright (C) 1999 Silicon Graphics, Inc.
  */
+#include <linux/errno.h>
 #include <asm/asm.h>
+#include <asm/asm-offsets.h>
 #include <asm/regdef.h>
 
 #ifdef CONFIG_64BIT
@@ -271,3 +273,443 @@ small_csumcpy:
         jr      ra
         .set    noreorder
         END(csum_partial)
+
+
+/*
+ * checksum and copy routines based on memcpy.S
+ *
+ *      csum_partial_copy_nocheck(src, dst, len, sum)
+ *      __csum_partial_copy_user(src, dst, len, sum, errp)
+ *
+ * See "Spec" in memcpy.S for details.  Unlike __copy_user, all
+ * function in this file use the standard calling convention.
+ */
+
+#define src a0
+#define dst a1
+#define len a2
+#define psum a3
+#define sum v0
+#define odd t8
+#define errptr t9
+
+/*
+ * The exception handler for loads requires that:
+ *  1- AT contain the address of the byte just past the end of the source
+ *     of the copy,
+ *  2- src_entry <= src < AT, and
+ *  3- (dst - src) == (dst_entry - src_entry),
+ * The _entry suffix denotes values when __copy_user was called.
+ *
+ * (1) is set up up by __csum_partial_copy_from_user and maintained by
+ *      not writing AT in __csum_partial_copy
+ * (2) is met by incrementing src by the number of bytes copied
+ * (3) is met by not doing loads between a pair of increments of dst and src
+ *
+ * The exception handlers for stores stores -EFAULT to errptr and return.
+ * These handlers do not need to overwrite any data.
+ */
+
+#define EXC(inst_reg,addr,handler)              \
+9:      inst_reg, addr;                         \
+        .section __ex_table,"a";                \
+        PTR     9b, handler;                    \
+        .previous
+
+#ifdef USE_DOUBLE
+
+#define LOAD   ld
+#define LOADL  ldl
+#define LOADR  ldr
+#define STOREL sdl
+#define STORER sdr
+#define STORE  sd
+#define ADD    daddu
+#define SUB    dsubu
+#define SRL    dsrl
+#define SLL    dsll
+#define SLLV   dsllv
+#define SRLV   dsrlv
+#define NBYTES 8
+#define LOG_NBYTES 3
+
+#else
+
+#define LOAD   lw
+#define LOADL  lwl
+#define LOADR  lwr
+#define STOREL swl
+#define STORER swr
+#define STORE  sw
+#define ADD    addu
+#define SUB    subu
+#define SRL    srl
+#define SLL    sll
+#define SLLV   sllv
+#define SRLV   srlv
+#define NBYTES 4
+#define LOG_NBYTES 2
+
+#endif /* USE_DOUBLE */
+
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+#define LDFIRST LOADR
+#define LDREST  LOADL
+#define STFIRST STORER
+#define STREST  STOREL
+#define SHIFT_DISCARD SLLV
+#define SHIFT_DISCARD_REVERT SRLV
+#else
+#define LDFIRST LOADL
+#define LDREST  LOADR
+#define STFIRST STOREL
+#define STREST  STORER
+#define SHIFT_DISCARD SRLV
+#define SHIFT_DISCARD_REVERT SLLV
+#endif
+
+#define FIRST(unit) ((unit)*NBYTES)
+#define REST(unit)  (FIRST(unit)+NBYTES-1)
+
+#define ADDRMASK (NBYTES-1)
+
+        .set    noat
+
+LEAF(__csum_partial_copy_user)
+        PTR_ADDU        AT, src, len    /* See (1) above. */
+#ifdef CONFIG_64BIT
+        move    errptr, a4
+#else
+        lw      errptr, 16(sp)
+#endif
+FEXPORT(csum_partial_copy_nocheck)
+        move    sum, zero
+        move    odd, zero
+        /*
+         * Note: dst & src may be unaligned, len may be 0
+         * Temps
+         */
+        /*
+         * The "issue break"s below are very approximate.
+         * Issue delays for dcache fills will perturb the schedule, as will
+         * load queue full replay traps, etc.
+         *
+         * If len < NBYTES use byte operations.
+         */
+        sltu    t2, len, NBYTES
+        and     t1, dst, ADDRMASK
+        bnez    t2, copy_bytes_checklen
+         and    t0, src, ADDRMASK
+        andi    odd, dst, 0x1                   /* odd buffer? */
+        bnez    t1, dst_unaligned
+         nop
+        bnez    t0, src_unaligned_dst_aligned
+        /*
+         * use delay slot for fall-through
+         * src and dst are aligned; need to compute rem
+         */
+both_aligned:
+         SRL    t0, len, LOG_NBYTES+3    # +3 for 8 units/iter
+        beqz    t0, cleanup_both_aligned # len < 8*NBYTES
+         nop
+        SUB     len, 8*NBYTES           # subtract here for bgez loop
+        .align  4
+1:
+EXC(    LOAD    t0, UNIT(0)(src),       l_exc)
+EXC(    LOAD    t1, UNIT(1)(src),       l_exc_copy)
+EXC(    LOAD    t2, UNIT(2)(src),       l_exc_copy)
+EXC(    LOAD    t3, UNIT(3)(src),       l_exc_copy)
+EXC(    LOAD    t4, UNIT(4)(src),       l_exc_copy)
+EXC(    LOAD    t5, UNIT(5)(src),       l_exc_copy)
+EXC(    LOAD    t6, UNIT(6)(src),       l_exc_copy)
+EXC(    LOAD    t7, UNIT(7)(src),       l_exc_copy)
+        SUB     len, len, 8*NBYTES
+        ADD     src, src, 8*NBYTES
+EXC(    STORE   t0, UNIT(0)(dst),       s_exc)
+        ADDC(sum, t0)
+EXC(    STORE   t1, UNIT(1)(dst),       s_exc)
+        ADDC(sum, t1)
+EXC(    STORE   t2, UNIT(2)(dst),       s_exc)
+        ADDC(sum, t2)
+EXC(    STORE   t3, UNIT(3)(dst),       s_exc)
+        ADDC(sum, t3)
+EXC(    STORE   t4, UNIT(4)(dst),       s_exc)
+        ADDC(sum, t4)
+EXC(    STORE   t5, UNIT(5)(dst),       s_exc)
+        ADDC(sum, t5)
+EXC(    STORE   t6, UNIT(6)(dst),       s_exc)
+        ADDC(sum, t6)
+EXC(    STORE   t7, UNIT(7)(dst),       s_exc)
+        ADDC(sum, t7)
+        bgez    len, 1b
+         ADD    dst, dst, 8*NBYTES
+        ADD     len, 8*NBYTES           # revert len (see above)
+
+        /*
+         * len == the number of bytes left to copy < 8*NBYTES
+         */
+cleanup_both_aligned:
+#define rem t7
+        beqz    len, done
+         sltu   t0, len, 4*NBYTES
+        bnez    t0, less_than_4units
+         and    rem, len, (NBYTES-1)    # rem = len % NBYTES
+        /*
+         * len >= 4*NBYTES
+         */
+EXC(    LOAD    t0, UNIT(0)(src),       l_exc)
+EXC(    LOAD    t1, UNIT(1)(src),       l_exc_copy)
+EXC(    LOAD    t2, UNIT(2)(src),       l_exc_copy)
+EXC(    LOAD    t3, UNIT(3)(src),       l_exc_copy)
+        SUB     len, len, 4*NBYTES
+        ADD     src, src, 4*NBYTES
+EXC(    STORE   t0, UNIT(0)(dst),       s_exc)
+        ADDC(sum, t0)
+EXC(    STORE   t1, UNIT(1)(dst),       s_exc)
+        ADDC(sum, t1)
+EXC(    STORE   t2, UNIT(2)(dst),       s_exc)
+        ADDC(sum, t2)
+EXC(    STORE   t3, UNIT(3)(dst),       s_exc)
+        ADDC(sum, t3)
+        beqz    len, done
+         ADD    dst, dst, 4*NBYTES
+less_than_4units:
+        /*
+         * rem = len % NBYTES
+         */
+        beq     rem, len, copy_bytes
+         nop
+1:
+EXC(    LOAD    t0, 0(src),             l_exc)
+        ADD     src, src, NBYTES
+        SUB     len, len, NBYTES
+EXC(    STORE   t0, 0(dst),             s_exc)
+        ADDC(sum, t0)
+        bne     rem, len, 1b
+         ADD    dst, dst, NBYTES
+
+        /*
+         * src and dst are aligned, need to copy rem bytes (rem < NBYTES)
+         * A loop would do only a byte at a time with possible branch
+         * mispredicts.  Can't do an explicit LOAD dst,mask,or,STORE
+         * because can't assume read-access to dst.  Instead, use
+         * STREST dst, which doesn't require read access to dst.
+         *
+         * This code should perform better than a simple loop on modern,
+         * wide-issue mips processors because the code has fewer branches and
+         * more instruction-level parallelism.
+         */
+#define bits t2
+        beqz    len, done
+         ADD    t1, dst, len    # t1 is just past last byte of dst
+        li      bits, 8*NBYTES
+        SLL     rem, len, 3     # rem = number of bits to keep
+EXC(    LOAD    t0, 0(src),             l_exc)
+        SUB     bits, bits, rem # bits = number of bits to discard
+        SHIFT_DISCARD t0, t0, bits
+EXC(    STREST  t0, -1(t1),             s_exc)
+        SHIFT_DISCARD_REVERT t0, t0, bits
+        .set reorder
+        ADDC(sum, t0)
+        b       done
+        .set noreorder
+dst_unaligned:
+        /*
+         * dst is unaligned
+         * t0 = src & ADDRMASK
+         * t1 = dst & ADDRMASK; T1 > 0
+         * len >= NBYTES
+         *
+         * Copy enough bytes to align dst
+         * Set match = (src and dst have same alignment)
+         */
+#define match rem
+EXC(    LDFIRST t3, FIRST(0)(src),      l_exc)
+        ADD     t2, zero, NBYTES
+EXC(    LDREST  t3, REST(0)(src),       l_exc_copy)
+        SUB     t2, t2, t1      # t2 = number of bytes copied
+        xor     match, t0, t1
+EXC(    STFIRST t3, FIRST(0)(dst),      s_exc)
+        SLL     t4, t1, 3               # t4 = number of bits to discard
+        SHIFT_DISCARD t3, t3, t4
+        /* no SHIFT_DISCARD_REVERT to handle odd buffer properly */
+        ADDC(sum, t3)
+        beq     len, t2, done
+         SUB    len, len, t2
+        ADD     dst, dst, t2
+        beqz    match, both_aligned
+         ADD    src, src, t2
+
+src_unaligned_dst_aligned:
+        SRL     t0, len, LOG_NBYTES+2    # +2 for 4 units/iter
+        beqz    t0, cleanup_src_unaligned
+         and    rem, len, (4*NBYTES-1)   # rem = len % 4*NBYTES
+1:
+/*
+ * Avoid consecutive LD*'s to the same register since some mips
+ * implementations can't issue them in the same cycle.
+ * It's OK to load FIRST(N+1) before REST(N) because the two addresses
+ * are to the same unit (unless src is aligned, but it's not).
+ */
+EXC(    LDFIRST t0, FIRST(0)(src),      l_exc)
+EXC(    LDFIRST t1, FIRST(1)(src),      l_exc_copy)
+        SUB     len, len, 4*NBYTES
+EXC(    LDREST  t0, REST(0)(src),       l_exc_copy)
+EXC(    LDREST  t1, REST(1)(src),       l_exc_copy)
+EXC(    LDFIRST t2, FIRST(2)(src),      l_exc_copy)
+EXC(    LDFIRST t3, FIRST(3)(src),      l_exc_copy)
+EXC(    LDREST  t2, REST(2)(src),       l_exc_copy)
+EXC(    LDREST  t3, REST(3)(src),       l_exc_copy)
+        ADD     src, src, 4*NBYTES
+#ifdef CONFIG_CPU_SB1
+        nop                             # improves slotting
+#endif
+EXC(    STORE   t0, UNIT(0)(dst),       s_exc)
+        ADDC(sum, t0)
+EXC(    STORE   t1, UNIT(1)(dst),       s_exc)
+        ADDC(sum, t1)
+EXC(    STORE   t2, UNIT(2)(dst),       s_exc)
+        ADDC(sum, t2)
+EXC(    STORE   t3, UNIT(3)(dst),       s_exc)
+        ADDC(sum, t3)
+        bne     len, rem, 1b
+         ADD    dst, dst, 4*NBYTES
+
+cleanup_src_unaligned:
+        beqz    len, done
+         and    rem, len, NBYTES-1  # rem = len % NBYTES
+        beq     rem, len, copy_bytes
+         nop
+1:
+EXC(    LDFIRST t0, FIRST(0)(src),      l_exc)
+EXC(    LDREST  t0, REST(0)(src),       l_exc_copy)
+        ADD     src, src, NBYTES
+        SUB     len, len, NBYTES
+EXC(    STORE   t0, 0(dst),             s_exc)
+        ADDC(sum, t0)
+        bne     len, rem, 1b
+         ADD    dst, dst, NBYTES
+
+copy_bytes_checklen:
+        beqz    len, done
+         nop
+copy_bytes:
+        /* 0 < len < NBYTES  */
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+#define SHIFT_START 0
+#define SHIFT_INC 8
+#else
+#define SHIFT_START 8*(NBYTES-1)
+#define SHIFT_INC -8
+#endif
+        move    t2, zero        # partial word
+        li      t3, SHIFT_START # shift
+/* use l_exc_copy here to return correct sum on fault */
+#define COPY_BYTE(N)                    \
+EXC(    lbu     t0, N(src), l_exc_copy);        \
+        SUB     len, len, 1;            \
+EXC(    sb      t0, N(dst), s_exc);     \
+        SLLV    t0, t0, t3;             \
+        addu    t3, SHIFT_INC;          \
+        beqz    len, copy_bytes_done;   \
+         or     t2, t0
+
+        COPY_BYTE(0)
+        COPY_BYTE(1)
+#ifdef USE_DOUBLE
+        COPY_BYTE(2)
+        COPY_BYTE(3)
+        COPY_BYTE(4)
+        COPY_BYTE(5)
+#endif
+EXC(    lbu     t0, NBYTES-2(src), l_exc_copy)
+        SUB     len, len, 1
+EXC(    sb      t0, NBYTES-2(dst), s_exc)
+        SLLV    t0, t0, t3
+        or      t2, t0
+copy_bytes_done:
+        ADDC(sum, t2)
+done:
+        /* fold checksum */
+#ifdef USE_DOUBLE
+        dsll32  v1, sum, 0
+        daddu   sum, v1
+        sltu    v1, sum, v1
+        dsra32  sum, sum, 0
+        addu    sum, v1
+#endif
+        sll     v1, sum, 16
+        addu    sum, v1
+        sltu    v1, sum, v1
+        srl     sum, sum, 16
+        addu    sum, v1
+
+        /* odd buffer alignment? */
+        beqz    odd, 1f
+         nop
+        sll     v1, sum, 8
+        srl     sum, sum, 8
+        or      sum, v1
+        andi    sum, 0xffff
+1:
+        .set reorder
+        ADDC(sum, psum)
+        jr      ra
+        .set noreorder
+
+l_exc_copy:
+        /*
+         * Copy bytes from src until faulting load address (or until a
+         * lb faults)
+         *
+         * When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
+         * may be more than a byte beyond the last address.
+         * Hence, the lb below may get an exception.
+         *
+         * Assumes src < THREAD_BUADDR($28)
+         */
+        LOAD    t0, TI_TASK($28)
+         li     t2, SHIFT_START
+        LOAD    t0, THREAD_BUADDR(t0)
+1:
+EXC(    lbu     t1, 0(src),     l_exc)
+        ADD     src, src, 1
+        sb      t1, 0(dst)      # can't fault -- we're copy_from_user
+        SLLV    t1, t1, t2
+        addu    t2, SHIFT_INC
+        ADDC(sum, t1)
+        bne     src, t0, 1b
+         ADD    dst, dst, 1
+l_exc:
+        LOAD    t0, TI_TASK($28)
+         nop
+        LOAD    t0, THREAD_BUADDR(t0)   # t0 is just past last good address
+         nop
+        SUB     len, AT, t0             # len number of uncopied bytes
+        /*
+         * Here's where we rely on src and dst being incremented in tandem,
+         *   See (3) above.
+         * dst += (fault addr - src) to put dst at first byte to clear
+         */
+        ADD     dst, t0                 # compute start address in a1
+        SUB     dst, src
+        /*
+         * Clear len bytes starting at dst.  Can't call __bzero because it
+         * might modify len.  An inefficient loop for these rare times...
+         */
+        beqz    len, done
+         SUB    src, len, 1
+1:      sb      zero, 0(dst)
+        ADD     dst, dst, 1
+        bnez    src, 1b
+         SUB    src, src, 1
+        li      v1, -EFAULT
+        b       done
+         sw     v1, (errptr)
+
+s_exc:
+        li      v0, -1 /* invalid checksum */
+        li      v1, -EFAULT
+        jr      ra
+         sw     v1, (errptr)
+        END(__csum_partial_copy_user)
diff --git a/arch/mips/lib/csum_partial_copy.c b/arch/mips/lib/csum_partial_copy.c
deleted file mode 100644
index 06771040a267..000000000000
--- a/arch/mips/lib/csum_partial_copy.c
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1994, 1995 Waldorf Electronics GmbH
- * Copyright (C) 1998, 1999 Ralf Baechle
- */
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/types.h>
-#include <asm/byteorder.h>
-#include <asm/string.h>
-#include <asm/uaccess.h>
-#include <net/checksum.h>
-
-/*
- * copy while checksumming, otherwise like csum_partial
- */
-__wsum csum_partial_copy_nocheck(const void *src,
-        void *dst, int len, __wsum sum)
-{
-        /*
-         * It's 2:30 am and I don't feel like doing it real ...
-         * This is lots slower than the real thing (tm)
-         */
-        sum = csum_partial(src, len, sum);
-        memcpy(dst, src, len);
-
-        return sum;
-}
-
-EXPORT_SYMBOL(csum_partial_copy_nocheck);
-
-/*
- * Copy from userspace and compute checksum.  If we catch an exception
- * then zero the rest of the buffer.
- */
-__wsum csum_partial_copy_from_user (const void __user *src,
-        void *dst, int len, __wsum sum, int *err_ptr)
-{
-        int missing;
-
-        might_sleep();
-        missing = copy_from_user(dst, src, len);
-        if (missing) {
-                memset(dst + len - missing, 0, missing);
-                *err_ptr = -EFAULT;
-        }
-
-        return csum_partial(dst, len, sum);
-}
diff --git a/include/asm-mips/checksum.h b/include/asm-mips/checksum.h
index 9b768c3b96b3..24cdcc6eaab8 100644
--- a/include/asm-mips/checksum.h
+++ b/include/asm-mips/checksum.h
@@ -29,31 +29,38 @@
  */
 __wsum csum_partial(const void *buff, int len, __wsum sum);
 
+__wsum __csum_partial_copy_user(const void *src, void *dst,
+                                int len, __wsum sum, int *err_ptr);
+
 /*
  * this is a new version of the above that records errors it finds in *errp,
  * but continues and zeros the rest of the buffer.
  */
-__wsum csum_partial_copy_from_user(const void __user *src,
-                                         void *dst, int len,
-                                         __wsum sum, int *errp);
+static inline
+__wsum csum_partial_copy_from_user(const void __user *src, void *dst, int len,
+                                   __wsum sum, int *err_ptr)
+{
+        might_sleep();
+        return __csum_partial_copy_user((__force void *)src, dst,
+                                        len, sum, err_ptr);
+}
 
 /*
  * Copy and checksum to user
  */
 #define HAVE_CSUM_COPY_USER
-static inline __wsum csum_and_copy_to_user (const void *src, void __user *dst,
-                                                  int len, __wsum sum,
-                                                  int *err_ptr)
+static inline
+__wsum csum_and_copy_to_user(const void *src, void __user *dst, int len,
+                             __wsum sum, int *err_ptr)
 {
         might_sleep();
-        sum = csum_partial(src, len, sum);
-
-        if (copy_to_user(dst, src, len)) {
+        if (access_ok(VERIFY_WRITE, dst, len))
+                return __csum_partial_copy_user(src, (__force void *)dst,
+                                                len, sum, err_ptr);
+        if (len)
                 *err_ptr = -EFAULT;
-                return (__force __wsum)-1;
-        }
 
-        return sum;
+        return (__force __wsum)-1; /* invalid checksum */
 }
 
 /*