/*
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* arch/xtensa/lib/strncpy_user.S
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*
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* This file is subject to the terms and conditions of the GNU General
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* Public License. See the file "COPYING" in the main directory of
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* this archive for more details.
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*
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* Returns: -EFAULT if exception before terminator, N if the entire
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* buffer filled, else strlen.
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*
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* Copyright (C) 2002 Tensilica Inc.
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*/
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#include <linux/errno.h>
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#include <linux/linkage.h>
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#include <variant/core.h>
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#include <asm/asmmacro.h>
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/*
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* char *__strncpy_user(char *dst, const char *src, size_t len)
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*/
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#ifdef __XTENSA_EB__
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# define MASK0 0xff000000
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# define MASK1 0x00ff0000
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# define MASK2 0x0000ff00
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# define MASK3 0x000000ff
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#else
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# define MASK0 0x000000ff
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# define MASK1 0x0000ff00
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# define MASK2 0x00ff0000
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# define MASK3 0xff000000
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#endif
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# Register use
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# a0/ return address
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# a1/ stack pointer
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# a2/ return value
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# a3/ src
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# a4/ len
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# a5/ mask0
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# a6/ mask1
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# a7/ mask2
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# a8/ mask3
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# a9/ tmp
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# a10/ tmp
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# a11/ dst
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# a12/ tmp
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.text
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ENTRY(__strncpy_user)
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entry sp, 16 # minimal stack frame
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# a2/ dst, a3/ src, a4/ len
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mov a11, a2 # leave dst in return value register
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beqz a4, .Lret # if len is zero
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movi a5, MASK0 # mask for byte 0
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movi a6, MASK1 # mask for byte 1
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movi a7, MASK2 # mask for byte 2
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movi a8, MASK3 # mask for byte 3
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bbsi.l a3, 0, .Lsrc1mod2 # if only 8-bit aligned
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bbsi.l a3, 1, .Lsrc2mod4 # if only 16-bit aligned
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.Lsrcaligned: # return here when src is word-aligned
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srli a12, a4, 2 # number of loop iterations with 4B per loop
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movi a9, 3
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bnone a11, a9, .Laligned
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j .Ldstunaligned
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.Lsrc1mod2: # src address is odd
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EX(11f) l8ui a9, a3, 0 # get byte 0
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addi a3, a3, 1 # advance src pointer
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EX(10f) s8i a9, a11, 0 # store byte 0
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beqz a9, .Lret # if byte 0 is zero
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addi a11, a11, 1 # advance dst pointer
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addi a4, a4, -1 # decrement len
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beqz a4, .Lret # if len is zero
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bbci.l a3, 1, .Lsrcaligned # if src is now word-aligned
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.Lsrc2mod4: # src address is 2 mod 4
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EX(11f) l8ui a9, a3, 0 # get byte 0
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/* 1-cycle interlock */
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EX(10f) s8i a9, a11, 0 # store byte 0
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beqz a9, .Lret # if byte 0 is zero
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addi a11, a11, 1 # advance dst pointer
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addi a4, a4, -1 # decrement len
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beqz a4, .Lret # if len is zero
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EX(11f) l8ui a9, a3, 1 # get byte 0
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addi a3, a3, 2 # advance src pointer
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EX(10f) s8i a9, a11, 0 # store byte 0
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beqz a9, .Lret # if byte 0 is zero
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addi a11, a11, 1 # advance dst pointer
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addi a4, a4, -1 # decrement len
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bnez a4, .Lsrcaligned # if len is nonzero
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.Lret:
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sub a2, a11, a2 # compute strlen
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retw
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/*
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* dst is word-aligned, src is word-aligned
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*/
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.align 4 # 1 mod 4 alignment for LOOPNEZ
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.byte 0 # (0 mod 4 alignment for LBEG)
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.Laligned:
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#if XCHAL_HAVE_LOOPS
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loopnez a12, .Loop1done
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#else
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beqz a12, .Loop1done
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slli a12, a12, 2
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add a12, a12, a11 # a12 = end of last 4B chunck
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#endif
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.Loop1:
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EX(11f) l32i a9, a3, 0 # get word from src
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addi a3, a3, 4 # advance src pointer
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bnone a9, a5, .Lz0 # if byte 0 is zero
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bnone a9, a6, .Lz1 # if byte 1 is zero
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bnone a9, a7, .Lz2 # if byte 2 is zero
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EX(10f) s32i a9, a11, 0 # store word to dst
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bnone a9, a8, .Lz3 # if byte 3 is zero
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addi a11, a11, 4 # advance dst pointer
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#if !XCHAL_HAVE_LOOPS
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blt a11, a12, .Loop1
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#endif
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.Loop1done:
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bbci.l a4, 1, .L100
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# copy 2 bytes
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EX(11f) l16ui a9, a3, 0
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addi a3, a3, 2 # advance src pointer
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#ifdef __XTENSA_EB__
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bnone a9, a7, .Lz0 # if byte 2 is zero
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bnone a9, a8, .Lz1 # if byte 3 is zero
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#else
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bnone a9, a5, .Lz0 # if byte 0 is zero
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bnone a9, a6, .Lz1 # if byte 1 is zero
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#endif
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EX(10f) s16i a9, a11, 0
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addi a11, a11, 2 # advance dst pointer
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.L100:
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bbci.l a4, 0, .Lret
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EX(11f) l8ui a9, a3, 0
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/* slot */
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EX(10f) s8i a9, a11, 0
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beqz a9, .Lret # if byte is zero
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addi a11, a11, 1-3 # advance dst ptr 1, but also cancel
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# the effect of adding 3 in .Lz3 code
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/* fall thru to .Lz3 and "retw" */
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.Lz3: # byte 3 is zero
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addi a11, a11, 3 # advance dst pointer
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sub a2, a11, a2 # compute strlen
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retw
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.Lz0: # byte 0 is zero
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#ifdef __XTENSA_EB__
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movi a9, 0
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#endif /* __XTENSA_EB__ */
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EX(10f) s8i a9, a11, 0
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sub a2, a11, a2 # compute strlen
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retw
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.Lz1: # byte 1 is zero
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#ifdef __XTENSA_EB__
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extui a9, a9, 16, 16
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#endif /* __XTENSA_EB__ */
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EX(10f) s16i a9, a11, 0
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addi a11, a11, 1 # advance dst pointer
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sub a2, a11, a2 # compute strlen
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retw
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.Lz2: # byte 2 is zero
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#ifdef __XTENSA_EB__
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extui a9, a9, 16, 16
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#endif /* __XTENSA_EB__ */
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EX(10f) s16i a9, a11, 0
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movi a9, 0
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EX(10f) s8i a9, a11, 2
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addi a11, a11, 2 # advance dst pointer
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sub a2, a11, a2 # compute strlen
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retw
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.align 4 # 1 mod 4 alignment for LOOPNEZ
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.byte 0 # (0 mod 4 alignment for LBEG)
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.Ldstunaligned:
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/*
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* for now just use byte copy loop
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*/
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#if XCHAL_HAVE_LOOPS
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loopnez a4, .Lunalignedend
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#else
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beqz a4, .Lunalignedend
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add a12, a11, a4 # a12 = ending address
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#endif /* XCHAL_HAVE_LOOPS */
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.Lnextbyte:
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EX(11f) l8ui a9, a3, 0
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addi a3, a3, 1
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EX(10f) s8i a9, a11, 0
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beqz a9, .Lunalignedend
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addi a11, a11, 1
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#if !XCHAL_HAVE_LOOPS
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blt a11, a12, .Lnextbyte
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#endif
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.Lunalignedend:
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sub a2, a11, a2 # compute strlen
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retw
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ENDPROC(__strncpy_user)
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.section .fixup, "ax"
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.align 4
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/* For now, just return -EFAULT. Future implementations might
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* like to clear remaining kernel space, like the fixup
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* implementation in memset(). Thus, we differentiate between
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* load/store fixups. */
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10:
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11:
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movi a2, -EFAULT
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retw
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