/*
* 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
