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strncpy_user.S
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/*
* arch/xtensa/lib/strncpy_user.S
*
* 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.
*
* Returns: -EFAULT if exception before terminator, N if the entire
* buffer filled, else strlen.
*
* Copyright (C) 2002 Tensilica Inc.
*/
#include <asm/variant/core.h>
#include <linux/errno.h>
/* 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
/*
* char *__strncpy_user(char *dst, const char *src, size_t len)
*/
#ifdef __XTENSA_EB__
# define MASK0 0xff000000
# define MASK1 0x00ff0000
# define MASK2 0x0000ff00
# define MASK3 0x000000ff
#else
# define MASK0 0x000000ff
# define MASK1 0x0000ff00
# define MASK2 0x00ff0000
# define MASK3 0xff000000
#endif
# Register use
# a0/ return address
# a1/ stack pointer
# a2/ return value
# a3/ src
# a4/ len
# a5/ mask0
# a6/ mask1
# a7/ mask2
# a8/ mask3
# a9/ tmp
# a10/ tmp
# a11/ dst
# a12/ tmp
.text
.align 4
.global __strncpy_user
.type __strncpy_user,@function
__strncpy_user:
entry sp, 16 # minimal stack frame
# a2/ dst, a3/ src, a4/ len
mov a11, a2 # leave dst in return value register
beqz a4, .Lret # if len is zero
movi a5, MASK0 # mask for byte 0
movi a6, MASK1 # mask for byte 1
movi a7, MASK2 # mask for byte 2
movi a8, MASK3 # mask for byte 3
bbsi.l a3, 0, .Lsrc1mod2 # if only 8-bit aligned
bbsi.l a3, 1, .Lsrc2mod4 # if only 16-bit aligned
.Lsrcaligned: # return here when src is word-aligned
srli a12, a4, 2 # number of loop iterations with 4B per loop
movi a9, 3
bnone a11, a9, .Laligned
j .Ldstunaligned
.Lsrc1mod2: # src address is odd
EX(l8ui, a9, a3, 0, fixup_l) # get byte 0
addi a3, a3, 1 # advance src pointer
EX(s8i, a9, a11, 0, fixup_s) # store byte 0
beqz a9, .Lret # if byte 0 is zero
addi a11, a11, 1 # advance dst pointer
addi a4, a4, -1 # decrement len
beqz a4, .Lret # if len is zero
bbci.l a3, 1, .Lsrcaligned # if src is now word-aligned
.Lsrc2mod4: # src address is 2 mod 4
EX(l8ui, a9, a3, 0, fixup_l) # get byte 0
/* 1-cycle interlock */
EX(s8i, a9, a11, 0, fixup_s) # store byte 0
beqz a9, .Lret # if byte 0 is zero
addi a11, a11, 1 # advance dst pointer
addi a4, a4, -1 # decrement len
beqz a4, .Lret # if len is zero
EX(l8ui, a9, a3, 1, fixup_l) # get byte 0
addi a3, a3, 2 # advance src pointer
EX(s8i, a9, a11, 0, fixup_s) # store byte 0
beqz a9, .Lret # if byte 0 is zero
addi a11, a11, 1 # advance dst pointer
addi a4, a4, -1 # decrement len
bnez a4, .Lsrcaligned # if len is nonzero
.Lret:
sub a2, a11, a2 # compute strlen
retw
/*
* dst is word-aligned, src is word-aligned
*/
.align 4 # 1 mod 4 alignment for LOOPNEZ
.byte 0 # (0 mod 4 alignment for LBEG)
.Laligned:
#if XCHAL_HAVE_LOOPS
loopnez a12, .Loop1done
#else
beqz a12, .Loop1done
slli a12, a12, 2
add a12, a12, a11 # a12 = end of last 4B chunck
#endif
.Loop1:
EX(l32i, a9, a3, 0, fixup_l) # get word from src
addi a3, a3, 4 # advance src pointer
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
bnone a9, a7, .Lz2 # if byte 2 is zero
EX(s32i, a9, a11, 0, fixup_s) # store word to dst
bnone a9, a8, .Lz3 # if byte 3 is zero
addi a11, a11, 4 # advance dst pointer
#if !XCHAL_HAVE_LOOPS
blt a11, a12, .Loop1
#endif
.Loop1done:
bbci.l a4, 1, .L100
# copy 2 bytes
EX(l16ui, a9, a3, 0, fixup_l)
addi a3, a3, 2 # advance src pointer
#ifdef __XTENSA_EB__
bnone a9, a7, .Lz0 # if byte 2 is zero
bnone a9, a8, .Lz1 # if byte 3 is zero
#else
bnone a9, a5, .Lz0 # if byte 0 is zero
bnone a9, a6, .Lz1 # if byte 1 is zero
#endif
EX(s16i, a9, a11, 0, fixup_s)
addi a11, a11, 2 # advance dst pointer
.L100:
bbci.l a4, 0, .Lret
EX(l8ui, a9, a3, 0, fixup_l)
/* slot */
EX(s8i, a9, a11, 0, fixup_s)
beqz a9, .Lret # if byte is zero
addi a11, a11, 1-3 # advance dst ptr 1, but also cancel
# the effect of adding 3 in .Lz3 code
/* fall thru to .Lz3 and "retw" */
.Lz3: # byte 3 is zero
addi a11, a11, 3 # advance dst pointer
sub a2, a11, a2 # compute strlen
retw
.Lz0: # byte 0 is zero
#ifdef __XTENSA_EB__
movi a9, 0
#endif /* __XTENSA_EB__ */
EX(s8i, a9, a11, 0, fixup_s)
sub a2, a11, a2 # compute strlen
retw
.Lz1: # byte 1 is zero
#ifdef __XTENSA_EB__
extui a9, a9, 16, 16
#endif /* __XTENSA_EB__ */
EX(s16i, a9, a11, 0, fixup_s)
addi a11, a11, 1 # advance dst pointer
sub a2, a11, a2 # compute strlen
retw
.Lz2: # byte 2 is zero
#ifdef __XTENSA_EB__
extui a9, a9, 16, 16
#endif /* __XTENSA_EB__ */
EX(s16i, a9, a11, 0, fixup_s)
movi a9, 0
EX(s8i, a9, a11, 2, fixup_s)
addi a11, a11, 2 # advance dst pointer
sub a2, a11, a2 # compute strlen
retw
.align 4 # 1 mod 4 alignment for LOOPNEZ
.byte 0 # (0 mod 4 alignment for LBEG)
.Ldstunaligned:
/*
* for now just use byte copy loop
*/
#if XCHAL_HAVE_LOOPS
loopnez a4, .Lunalignedend
#else
beqz a4, .Lunalignedend
add a12, a11, a4 # a12 = ending address
#endif /* XCHAL_HAVE_LOOPS */
.Lnextbyte:
EX(l8ui, a9, a3, 0, fixup_l)
addi a3, a3, 1
EX(s8i, a9, a11, 0, fixup_s)
beqz a9, .Lunalignedend
addi a11, a11, 1
#if !XCHAL_HAVE_LOOPS
blt a11, a12, .Lnextbyte
#endif
.Lunalignedend:
sub a2, a11, a2 # compute strlen
retw
.section .fixup, "ax"
.align 4
/* For now, just return -EFAULT. Future implementations might
* like to clear remaining kernel space, like the fixup
* implementation in memset(). Thus, we differentiate between
* load/store fixups. */
fixup_s:
fixup_l:
movi a2, -EFAULT
retw