/*
 *  arch/xtensa/lib/usercopy.S
 *
 *  Copy to/from user space (derived from arch/xtensa/lib/hal/memcopy.S)
 *
 *  DO NOT COMBINE this function with <arch/xtensa/lib/hal/memcopy.S>.
 *  It needs to remain separate and distinct.  The hal files are part
 *  of the Xtensa link-time HAL, and those files may differ per
 *  processor configuration.  Patching the kernel for another
 *  processor configuration includes replacing the hal files, and we
 *  could lose the special functionality for accessing user-space
 *  memory during such a patch.  We sacrifice a little code space here
 *  in favor to simplify code maintenance.
 *
 *  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) 2002 Tensilica Inc.
 */


/*
 * size_t __xtensa_copy_user (void *dst, const void *src, size_t len);
 *
 * The returned value is the number of bytes not copied.  Implies zero
 * is success.
 *
 * The general case algorithm is as follows:
 *   If the destination and source are both aligned,
 *     do 16B chunks with a loop, and then finish up with
 *     8B, 4B, 2B, and 1B copies conditional on the length.
 *   If destination is aligned and source unaligned,
 *     do the same, but use SRC to align the source data.
 *   If destination is unaligned, align it by conditionally
 *     copying 1B and 2B and then retest.
 *   This code tries to use fall-through braches for the common
 *     case of aligned destinations (except for the branches to
 *     the alignment label).
 *
 * Register use:
 *      a0/ return address
 *      a1/ stack pointer
 *      a2/ return value
 *      a3/ src
 *      a4/ length
 *      a5/ dst
 *      a6/ tmp
 *      a7/ tmp
 *      a8/ tmp
 *      a9/ tmp
 *      a10/ tmp
 *      a11/ original length
 */

#include <linux/linkage.h>
#include <asm/asmmacro.h>
#include <asm/core.h>

        .text
ENTRY(__xtensa_copy_user)

#if !XCHAL_HAVE_LOOPS && defined(__XTENSA_CALL0_ABI__)
#define STACK_SIZE 4
#else
#define STACK_SIZE 0
#endif
        abi_entry(STACK_SIZE)
        # a2/ dst, a3/ src, a4/ len
        mov     a5, a2          # copy dst so that a2 is return value
        mov     a11, a4         # preserve original len for error case
.Lcommon:
        bbsi.l  a2, 0, .Ldst1mod2 # if dst is 1 mod 2
        bbsi.l  a2, 1, .Ldst2mod4 # if dst is 2 mod 4
.Ldstaligned:   # return here from .Ldstunaligned when dst is aligned
        srli    a7, a4, 4       # number of loop iterations with 16B
                                # per iteration
        movi    a8, 3             # if source is also aligned,
        bnone   a3, a8, .Laligned # then use word copy
        __ssa8  a3              # set shift amount from byte offset
        bnez    a4, .Lsrcunaligned
        movi    a2, 0           # return success for len==0
        abi_ret(STACK_SIZE)

/*
 * Destination is unaligned
 */

.Ldst1mod2:     # dst is only byte aligned
        bltui   a4, 7, .Lbytecopy       # do short copies byte by byte

        # copy 1 byte
EX(10f) l8ui    a6, a3, 0
        addi    a3, a3,  1
EX(10f) s8i     a6, a5,  0
        addi    a5, a5,  1
        addi    a4, a4, -1
        bbci.l  a5, 1, .Ldstaligned     # if dst is now aligned, then
                                        # return to main algorithm
.Ldst2mod4:     # dst 16-bit aligned
        # copy 2 bytes
        bltui   a4, 6, .Lbytecopy       # do short copies byte by byte
EX(10f) l8ui    a6, a3, 0
EX(10f) l8ui    a7, a3, 1
        addi    a3, a3,  2
EX(10f) s8i     a6, a5,  0
EX(10f) s8i     a7, a5,  1
        addi    a5, a5,  2
        addi    a4, a4, -2
        j       .Ldstaligned    # dst is now aligned, return to main algorithm

/*
 * Byte by byte copy
 */
        .align  4
        .byte   0               # 1 mod 4 alignment for LOOPNEZ
                                # (0 mod 4 alignment for LBEG)
.Lbytecopy:
#if XCHAL_HAVE_LOOPS
        loopnez a4, .Lbytecopydone
#else /* !XCHAL_HAVE_LOOPS */
        beqz    a4, .Lbytecopydone
        add     a7, a3, a4      # a7 = end address for source
#endif /* !XCHAL_HAVE_LOOPS */
.Lnextbyte:
EX(10f) l8ui    a6, a3, 0
        addi    a3, a3, 1
EX(10f) s8i     a6, a5, 0
        addi    a5, a5, 1
#if !XCHAL_HAVE_LOOPS
        blt     a3, a7, .Lnextbyte
#endif /* !XCHAL_HAVE_LOOPS */
.Lbytecopydone:
        movi    a2, 0           # return success for len bytes copied
        abi_ret(STACK_SIZE)

/*
 * Destination and source are word-aligned.
 */
        # copy 16 bytes per iteration for word-aligned dst and word-aligned src
        .align  4               # 1 mod 4 alignment for LOOPNEZ
        .byte   0               # (0 mod 4 alignment for LBEG)
.Laligned:
#if XCHAL_HAVE_LOOPS
        loopnez a7, .Loop1done
#else /* !XCHAL_HAVE_LOOPS */
        beqz    a7, .Loop1done
        slli    a8, a7, 4
        add     a8, a8, a3      # a8 = end of last 16B source chunk
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1:
EX(10f) l32i    a6, a3,  0
EX(10f) l32i    a7, a3,  4
EX(10f) s32i    a6, a5,  0
EX(10f) l32i    a6, a3,  8
EX(10f) s32i    a7, a5,  4
EX(10f) l32i    a7, a3, 12
EX(10f) s32i    a6, a5,  8
        addi    a3, a3, 16
EX(10f) s32i    a7, a5, 12
        addi    a5, a5, 16
#if !XCHAL_HAVE_LOOPS
        blt     a3, a8, .Loop1
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1done:
        bbci.l  a4, 3, .L2
        # copy 8 bytes
EX(10f) l32i    a6, a3,  0
EX(10f) l32i    a7, a3,  4
        addi    a3, a3,  8
EX(10f) s32i    a6, a5,  0
EX(10f) s32i    a7, a5,  4
        addi    a5, a5,  8
.L2:
        bbci.l  a4, 2, .L3
        # copy 4 bytes
EX(10f) l32i    a6, a3,  0
        addi    a3, a3,  4
EX(10f) s32i    a6, a5,  0
        addi    a5, a5,  4
.L3:
        bbci.l  a4, 1, .L4
        # copy 2 bytes
EX(10f) l16ui   a6, a3,  0
        addi    a3, a3,  2
EX(10f) s16i    a6, a5,  0
        addi    a5, a5,  2
.L4:
        bbci.l  a4, 0, .L5
        # copy 1 byte
EX(10f) l8ui    a6, a3,  0
EX(10f) s8i     a6, a5,  0
.L5:
        movi    a2, 0           # return success for len bytes copied
        abi_ret(STACK_SIZE)

/*
 * Destination is aligned, Source is unaligned
 */

        .align  4
        .byte   0               # 1 mod 4 alignement for LOOPNEZ
                                # (0 mod 4 alignment for LBEG)
.Lsrcunaligned:
        # copy 16 bytes per iteration for word-aligned dst and unaligned src
        and     a10, a3, a8     # save unalignment offset for below
        sub     a3, a3, a10     # align a3 (to avoid sim warnings only; not needed for hardware)
EX(10f) l32i    a6, a3, 0       # load first word
#if XCHAL_HAVE_LOOPS
        loopnez a7, .Loop2done
#else /* !XCHAL_HAVE_LOOPS */
        beqz    a7, .Loop2done
#if defined(__XTENSA_CALL0_ABI__)
        s32i    a10, a1, 0
        slli    a10, a7, 4
        add     a10, a10, a3    # a10 = end of last 16B source chunk
#else
        slli    a12, a7, 4
        add     a12, a12, a3    # a12 = end of last 16B source chunk
#endif
#endif /* !XCHAL_HAVE_LOOPS */
.Loop2:
EX(10f) l32i    a7, a3,  4
EX(10f) l32i    a8, a3,  8
        __src_b a6, a6, a7
EX(10f) s32i    a6, a5,  0
EX(10f) l32i    a9, a3, 12
        __src_b a7, a7, a8
EX(10f) s32i    a7, a5,  4
EX(10f) l32i    a6, a3, 16
        __src_b a8, a8, a9
EX(10f) s32i    a8, a5,  8
        addi    a3, a3, 16
        __src_b a9, a9, a6
EX(10f) s32i    a9, a5, 12
        addi    a5, a5, 16
#if !XCHAL_HAVE_LOOPS
#if defined(__XTENSA_CALL0_ABI__)
        blt     a3, a10, .Loop2
        l32i    a10, a1, 0
#else
        blt     a3, a12, .Loop2
#endif
#endif /* !XCHAL_HAVE_LOOPS */
.Loop2done:
        bbci.l  a4, 3, .L12
        # copy 8 bytes
EX(10f) l32i    a7, a3,  4
EX(10f) l32i    a8, a3,  8
        __src_b a6, a6, a7
EX(10f) s32i    a6, a5,  0
        addi    a3, a3,  8
        __src_b a7, a7, a8
EX(10f) s32i    a7, a5,  4
        addi    a5, a5,  8
        mov     a6, a8
.L12:
        bbci.l  a4, 2, .L13
        # copy 4 bytes
EX(10f) l32i    a7, a3,  4
        addi    a3, a3,  4
        __src_b a6, a6, a7
EX(10f) s32i    a6, a5,  0
        addi    a5, a5,  4
        mov     a6, a7
.L13:
        add     a3, a3, a10     # readjust a3 with correct misalignment
        bbci.l  a4, 1, .L14
        # copy 2 bytes
EX(10f) l8ui    a6, a3,  0
EX(10f) l8ui    a7, a3,  1
        addi    a3, a3,  2
EX(10f) s8i     a6, a5,  0
EX(10f) s8i     a7, a5,  1
        addi    a5, a5,  2
.L14:
        bbci.l  a4, 0, .L15
        # copy 1 byte
EX(10f) l8ui    a6, a3,  0
EX(10f) s8i     a6, a5,  0
.L15:
        movi    a2, 0           # return success for len bytes copied
        abi_ret(STACK_SIZE)

ENDPROC(__xtensa_copy_user)
EXPORT_SYMBOL(__xtensa_copy_user)

        .section .fixup, "ax"
        .align  4

/* a2 = original dst; a5 = current dst; a11= original len
 * bytes_copied = a5 - a2
 * retval = bytes_not_copied = original len - bytes_copied
 * retval = a11 - (a5 - a2)
 */


10:
        sub     a2, a5, a2      /* a2 <-- bytes copied */
        sub     a2, a11, a2     /* a2 <-- bytes not copied */
        abi_ret(STACK_SIZE)