/*
   *  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 <variant/core.h>
  
  #ifdef __XTENSA_EB__
  #define ALIGN(R, W0, W1) src	R, W0, W1
  #define SSA8(R)	ssa8b R
  #else
  #define ALIGN(R, W0, W1) src	R, W1, W0
  #define SSA8(R)	ssa8l R
  #endif
  
  /* Load or store instructions that may cause exceptions use the EX macro. */
  
  #define EX(insn,reg1,reg2,offset,handler)	\
  9:	insn	reg1, reg2, offset;		\
  	.section __ex_table, "a";		\
  	.word	9b, handler;			\
  	.previous
  
  
  	.text
  	.align	4
  	.global	__xtensa_copy_user
  	.type	__xtensa_copy_user,@function
  __xtensa_copy_user:
  	entry	sp, 16		# minimal stack frame
  	# 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
  	retw
  
  /*
   * Destination is unaligned
   */
  
  .Ldst1mod2:	# dst is only byte aligned
  	bltui	a4, 7, .Lbytecopy	# do short copies byte by byte
  
  	# copy 1 byte
  	EX(l8ui, a6, a3, 0, l_fixup)
  	addi	a3, a3,  1
  	EX(s8i, a6, a5,  0, s_fixup)
  	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(l8ui, a6, a3, 0, l_fixup)
  	EX(l8ui, a7, a3, 1, l_fixup)
  	addi	a3, a3,  2
  	EX(s8i, a6, a5,  0, s_fixup)
  	EX(s8i, a7, a5,  1, s_fixup)
  	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(l8ui, a6, a3, 0, l_fixup)
  	addi	a3, a3, 1
  	EX(s8i, a6, a5, 0, s_fixup)
  	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
  	retw
  
  /*
   * 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(l32i, a6, a3,  0, l_fixup)
  	EX(l32i, a7, a3,  4, l_fixup)
  	EX(s32i, a6, a5,  0, s_fixup)
  	EX(l32i, a6, a3,  8, l_fixup)
  	EX(s32i, a7, a5,  4, s_fixup)
  	EX(l32i, a7, a3, 12, l_fixup)
  	EX(s32i, a6, a5,  8, s_fixup)
  	addi	a3, a3, 16
  	EX(s32i, a7, a5, 12, s_fixup)
  	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(l32i, a6, a3,  0, l_fixup)
  	EX(l32i, a7, a3,  4, l_fixup)
  	addi	a3, a3,  8
  	EX(s32i, a6, a5,  0, s_fixup)
  	EX(s32i, a7, a5,  4, s_fixup)
  	addi	a5, a5,  8
  .L2:
  	bbci.l	a4, 2, .L3
  	# copy 4 bytes
  	EX(l32i, a6, a3,  0, l_fixup)
  	addi	a3, a3,  4
  	EX(s32i, a6, a5,  0, s_fixup)
  	addi	a5, a5,  4
  .L3:
  	bbci.l	a4, 1, .L4
  	# copy 2 bytes
  	EX(l16ui, a6, a3,  0, l_fixup)
  	addi	a3, a3,  2
  	EX(s16i,  a6, a5,  0, s_fixup)
  	addi	a5, a5,  2
  .L4:
  	bbci.l	a4, 0, .L5
  	# copy 1 byte
  	EX(l8ui, a6, a3,  0, l_fixup)
  	EX(s8i,  a6, a5,  0, s_fixup)
  .L5:
  	movi	a2, 0		# return success for len bytes copied
  	retw
  
  /*
   * 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(l32i, a6, a3, 0, l_fixup)	# load first word
  #if XCHAL_HAVE_LOOPS
  	loopnez	a7, .Loop2done
  #else /* !XCHAL_HAVE_LOOPS */
  	beqz	a7, .Loop2done
  	slli	a10, a7, 4
  	add	a10, a10, a3	# a10 = end of last 16B source chunk
  #endif /* !XCHAL_HAVE_LOOPS */
  .Loop2:
  	EX(l32i, a7, a3,  4, l_fixup)
  	EX(l32i, a8, a3,  8, l_fixup)
  	ALIGN(	a6, a6, a7)
  	EX(s32i, a6, a5,  0, s_fixup)
  	EX(l32i, a9, a3, 12, l_fixup)
  	ALIGN(	a7, a7, a8)
  	EX(s32i, a7, a5,  4, s_fixup)
  	EX(l32i, a6, a3, 16, l_fixup)
  	ALIGN(	a8, a8, a9)
  	EX(s32i, a8, a5,  8, s_fixup)
  	addi	a3, a3, 16
  	ALIGN(	a9, a9, a6)
  	EX(s32i, a9, a5, 12, s_fixup)
  	addi	a5, a5, 16
  #if !XCHAL_HAVE_LOOPS
  	blt	a3, a10, .Loop2
  #endif /* !XCHAL_HAVE_LOOPS */
  .Loop2done:
  	bbci.l	a4, 3, .L12
  	# copy 8 bytes
  	EX(l32i, a7, a3,  4, l_fixup)
  	EX(l32i, a8, a3,  8, l_fixup)
  	ALIGN(	a6, a6, a7)
  	EX(s32i, a6, a5,  0, s_fixup)
  	addi	a3, a3,  8
  	ALIGN(	a7, a7, a8)
  	EX(s32i, a7, a5,  4, s_fixup)
  	addi	a5, a5,  8
  	mov	a6, a8
  .L12:
  	bbci.l	a4, 2, .L13
  	# copy 4 bytes
  	EX(l32i, a7, a3,  4, l_fixup)
  	addi	a3, a3,  4
  	ALIGN(	a6, a6, a7)
  	EX(s32i, a6, a5,  0, s_fixup)
  	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(l8ui, a6, a3,  0, l_fixup)
  	EX(l8ui, a7, a3,  1, l_fixup)
  	addi	a3, a3,  2
  	EX(s8i, a6, a5,  0, s_fixup)
  	EX(s8i, a7, a5,  1, s_fixup)
  	addi	a5, a5,  2
  .L14:
  	bbci.l	a4, 0, .L15
  	# copy 1 byte
  	EX(l8ui, a6, a3,  0, l_fixup)
  	EX(s8i,  a6, a5,  0, s_fixup)
  .L15:
  	movi	a2, 0		# return success for len bytes copied
  	retw
  
  
  	.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)
   *
   * Clearing the remaining pieces of kernel memory plugs security
   * holes.  This functionality is the equivalent of the *_zeroing
   * functions that some architectures provide.
   */
  
  .Lmemset:
  	.word	memset
  
  s_fixup:
  	sub	a2, a5, a2	/* a2 <-- bytes copied */
  	sub	a2, a11, a2	/* a2 <-- bytes not copied */
  	retw
  
  l_fixup:
  	sub	a2, a5, a2	/* a2 <-- bytes copied */
  	sub	a2, a11, a2	/* a2 <-- bytes not copied == return value */
  
  	/* void *memset(void *s, int c, size_t n); */
  	mov	a6, a5		/* s */
  	movi	a7, 0		/* c */
  	mov	a8, a2		/* n */
  	l32r	a4, .Lmemset
  	callx4	a4
  	/* Ignore memset return value in a6. */
  	/* a2 still contains bytes not copied. */
  	retw