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436 lines
11 KiB
436 lines
11 KiB
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Unified implementation of memcpy, memmove and the __copy_user backend.
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*
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* Copyright (C) 1998, 99, 2000, 01, 2002 Ralf Baechle (ralf@gnu.org)
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* Copyright (C) 1999, 2000, 01, 2002 Silicon Graphics, Inc.
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* Copyright (C) 2002 Broadcom, Inc.
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* memcpy/copy_user author: Mark Vandevoorde
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*
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* Mnemonic names for arguments to memcpy/__copy_user
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*/
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/*
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* Hack to resolve longstanding prefetch issue
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*
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* Prefetching may be fatal on some systems if we're prefetching beyond the
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* end of memory on some systems. It's also a seriously bad idea on non
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* dma-coherent systems.
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*/
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#if !defined(CONFIG_DMA_COHERENT) || !defined(CONFIG_DMA_IP27)
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#undef CONFIG_CPU_HAS_PREFETCH
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#endif
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#ifdef CONFIG_MIPS_MALTA
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#undef CONFIG_CPU_HAS_PREFETCH
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#endif
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#include <asm/asm.h>
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#include <asm/asm-offsets.h>
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#include <asm/regdef.h>
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#define dst a0
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#define src a1
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#define len a2
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/*
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* Spec
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*
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* memcpy copies len bytes from src to dst and sets v0 to dst.
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* It assumes that
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* - src and dst don't overlap
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* - src is readable
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* - dst is writable
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* memcpy uses the standard calling convention
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*
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* __copy_user copies up to len bytes from src to dst and sets a2 (len) to
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* the number of uncopied bytes due to an exception caused by a read or write.
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* __copy_user assumes that src and dst don't overlap, and that the call is
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* implementing one of the following:
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* copy_to_user
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* - src is readable (no exceptions when reading src)
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* copy_from_user
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* - dst is writable (no exceptions when writing dst)
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* __copy_user uses a non-standard calling convention; see
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* include/asm-mips/uaccess.h
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*
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* When an exception happens on a load, the handler must
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# ensure that all of the destination buffer is overwritten to prevent
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* leaking information to user mode programs.
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*/
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/*
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* Implementation
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*/
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/*
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* The exception handler for loads requires that:
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* 1- AT contain the address of the byte just past the end of the source
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* of the copy,
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* 2- src_entry <= src < AT, and
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* 3- (dst - src) == (dst_entry - src_entry),
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* The _entry suffix denotes values when __copy_user was called.
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*
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* (1) is set up up by uaccess.h and maintained by not writing AT in copy_user
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* (2) is met by incrementing src by the number of bytes copied
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* (3) is met by not doing loads between a pair of increments of dst and src
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*
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* The exception handlers for stores adjust len (if necessary) and return.
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* These handlers do not need to overwrite any data.
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*
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* For __rmemcpy and memmove an exception is always a kernel bug, therefore
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* they're not protected.
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*/
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#define EXC(inst_reg,addr,handler) \
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9: inst_reg, addr; \
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.section __ex_table,"a"; \
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PTR 9b, handler; \
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.previous
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/*
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* Only on the 64-bit kernel we can made use of 64-bit registers.
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*/
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#ifdef CONFIG_64BIT
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#define USE_DOUBLE
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#endif
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#ifdef USE_DOUBLE
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#define LOAD ld
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#define LOADL ldl
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#define LOADR ldr
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#define STOREL sdl
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#define STORER sdr
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#define STORE sd
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#define ADD daddu
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#define SUB dsubu
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#define SRL dsrl
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#define SRA dsra
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#define SLL dsll
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#define SLLV dsllv
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#define SRLV dsrlv
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#define NBYTES 8
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#define LOG_NBYTES 3
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/*
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* As we are sharing code base with the mips32 tree (which use the o32 ABI
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* register definitions). We need to redefine the register definitions from
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* the n64 ABI register naming to the o32 ABI register naming.
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*/
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#undef t0
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#undef t1
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#undef t2
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#undef t3
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#define t0 $8
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#define t1 $9
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#define t2 $10
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#define t3 $11
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#define t4 $12
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#define t5 $13
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#define t6 $14
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#define t7 $15
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#else
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#define LOAD lw
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#define LOADL lwl
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#define LOADR lwr
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#define STOREL swl
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#define STORER swr
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#define STORE sw
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#define ADD addu
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#define SUB subu
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#define SRL srl
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#define SLL sll
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#define SRA sra
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#define SLLV sllv
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#define SRLV srlv
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#define NBYTES 4
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#define LOG_NBYTES 2
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#endif /* USE_DOUBLE */
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#ifdef CONFIG_CPU_LITTLE_ENDIAN
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#define LDFIRST LOADR
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#define LDREST LOADL
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#define STFIRST STORER
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#define STREST STOREL
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#define SHIFT_DISCARD SLLV
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#else
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#define LDFIRST LOADL
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#define LDREST LOADR
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#define STFIRST STOREL
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#define STREST STORER
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#define SHIFT_DISCARD SRLV
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#endif
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#define FIRST(unit) ((unit)*NBYTES)
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#define REST(unit) (FIRST(unit)+NBYTES-1)
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#define UNIT(unit) FIRST(unit)
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#define ADDRMASK (NBYTES-1)
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.text
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.set noreorder
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.set noat
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/*
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* A combined memcpy/__copy_user
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* __copy_user sets len to 0 for success; else to an upper bound of
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* the number of uncopied bytes.
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* memcpy sets v0 to dst.
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*/
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.align 5
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LEAF(__copy_user_inatomic)
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/*
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* Note: dst & src may be unaligned, len may be 0
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* Temps
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*/
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#define rem t8
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/*
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* The "issue break"s below are very approximate.
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* Issue delays for dcache fills will perturb the schedule, as will
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* load queue full replay traps, etc.
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*
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* If len < NBYTES use byte operations.
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*/
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PREF( 0, 0(src) )
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PREF( 1, 0(dst) )
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sltu t2, len, NBYTES
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and t1, dst, ADDRMASK
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PREF( 0, 1*32(src) )
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PREF( 1, 1*32(dst) )
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bnez t2, copy_bytes_checklen
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and t0, src, ADDRMASK
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PREF( 0, 2*32(src) )
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PREF( 1, 2*32(dst) )
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bnez t1, dst_unaligned
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nop
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bnez t0, src_unaligned_dst_aligned
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/*
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* use delay slot for fall-through
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* src and dst are aligned; need to compute rem
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*/
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both_aligned:
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SRL t0, len, LOG_NBYTES+3 # +3 for 8 units/iter
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beqz t0, cleanup_both_aligned # len < 8*NBYTES
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and rem, len, (8*NBYTES-1) # rem = len % (8*NBYTES)
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PREF( 0, 3*32(src) )
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PREF( 1, 3*32(dst) )
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.align 4
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1:
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EXC( LOAD t0, UNIT(0)(src), l_exc)
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EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
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EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
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EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
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SUB len, len, 8*NBYTES
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EXC( LOAD t4, UNIT(4)(src), l_exc_copy)
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EXC( LOAD t7, UNIT(5)(src), l_exc_copy)
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STORE t0, UNIT(0)(dst)
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STORE t1, UNIT(1)(dst)
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EXC( LOAD t0, UNIT(6)(src), l_exc_copy)
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EXC( LOAD t1, UNIT(7)(src), l_exc_copy)
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ADD src, src, 8*NBYTES
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ADD dst, dst, 8*NBYTES
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STORE t2, UNIT(-6)(dst)
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STORE t3, UNIT(-5)(dst)
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STORE t4, UNIT(-4)(dst)
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STORE t7, UNIT(-3)(dst)
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STORE t0, UNIT(-2)(dst)
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STORE t1, UNIT(-1)(dst)
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PREF( 0, 8*32(src) )
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PREF( 1, 8*32(dst) )
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bne len, rem, 1b
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nop
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/*
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* len == rem == the number of bytes left to copy < 8*NBYTES
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*/
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cleanup_both_aligned:
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beqz len, done
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sltu t0, len, 4*NBYTES
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bnez t0, less_than_4units
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and rem, len, (NBYTES-1) # rem = len % NBYTES
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/*
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* len >= 4*NBYTES
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*/
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EXC( LOAD t0, UNIT(0)(src), l_exc)
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EXC( LOAD t1, UNIT(1)(src), l_exc_copy)
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EXC( LOAD t2, UNIT(2)(src), l_exc_copy)
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EXC( LOAD t3, UNIT(3)(src), l_exc_copy)
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SUB len, len, 4*NBYTES
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ADD src, src, 4*NBYTES
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STORE t0, UNIT(0)(dst)
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STORE t1, UNIT(1)(dst)
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STORE t2, UNIT(2)(dst)
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STORE t3, UNIT(3)(dst)
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beqz len, done
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ADD dst, dst, 4*NBYTES
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less_than_4units:
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/*
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* rem = len % NBYTES
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*/
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beq rem, len, copy_bytes
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nop
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1:
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EXC( LOAD t0, 0(src), l_exc)
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ADD src, src, NBYTES
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SUB len, len, NBYTES
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STORE t0, 0(dst)
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bne rem, len, 1b
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ADD dst, dst, NBYTES
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/*
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* src and dst are aligned, need to copy rem bytes (rem < NBYTES)
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* A loop would do only a byte at a time with possible branch
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* mispredicts. Can't do an explicit LOAD dst,mask,or,STORE
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* because can't assume read-access to dst. Instead, use
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* STREST dst, which doesn't require read access to dst.
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*
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* This code should perform better than a simple loop on modern,
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* wide-issue mips processors because the code has fewer branches and
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* more instruction-level parallelism.
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*/
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#define bits t2
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beqz len, done
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ADD t1, dst, len # t1 is just past last byte of dst
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li bits, 8*NBYTES
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SLL rem, len, 3 # rem = number of bits to keep
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EXC( LOAD t0, 0(src), l_exc)
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SUB bits, bits, rem # bits = number of bits to discard
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SHIFT_DISCARD t0, t0, bits
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STREST t0, -1(t1)
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jr ra
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move len, zero
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dst_unaligned:
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/*
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* dst is unaligned
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* t0 = src & ADDRMASK
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* t1 = dst & ADDRMASK; T1 > 0
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* len >= NBYTES
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*
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* Copy enough bytes to align dst
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* Set match = (src and dst have same alignment)
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*/
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#define match rem
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EXC( LDFIRST t3, FIRST(0)(src), l_exc)
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ADD t2, zero, NBYTES
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EXC( LDREST t3, REST(0)(src), l_exc_copy)
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SUB t2, t2, t1 # t2 = number of bytes copied
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xor match, t0, t1
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STFIRST t3, FIRST(0)(dst)
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beq len, t2, done
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SUB len, len, t2
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ADD dst, dst, t2
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beqz match, both_aligned
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ADD src, src, t2
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src_unaligned_dst_aligned:
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SRL t0, len, LOG_NBYTES+2 # +2 for 4 units/iter
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PREF( 0, 3*32(src) )
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beqz t0, cleanup_src_unaligned
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and rem, len, (4*NBYTES-1) # rem = len % 4*NBYTES
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PREF( 1, 3*32(dst) )
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1:
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/*
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* Avoid consecutive LD*'s to the same register since some mips
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* implementations can't issue them in the same cycle.
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* It's OK to load FIRST(N+1) before REST(N) because the two addresses
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* are to the same unit (unless src is aligned, but it's not).
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*/
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EXC( LDFIRST t0, FIRST(0)(src), l_exc)
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EXC( LDFIRST t1, FIRST(1)(src), l_exc_copy)
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SUB len, len, 4*NBYTES
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EXC( LDREST t0, REST(0)(src), l_exc_copy)
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EXC( LDREST t1, REST(1)(src), l_exc_copy)
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EXC( LDFIRST t2, FIRST(2)(src), l_exc_copy)
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EXC( LDFIRST t3, FIRST(3)(src), l_exc_copy)
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EXC( LDREST t2, REST(2)(src), l_exc_copy)
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EXC( LDREST t3, REST(3)(src), l_exc_copy)
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PREF( 0, 9*32(src) ) # 0 is PREF_LOAD (not streamed)
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ADD src, src, 4*NBYTES
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#ifdef CONFIG_CPU_SB1
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nop # improves slotting
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#endif
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STORE t0, UNIT(0)(dst)
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STORE t1, UNIT(1)(dst)
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STORE t2, UNIT(2)(dst)
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STORE t3, UNIT(3)(dst)
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PREF( 1, 9*32(dst) ) # 1 is PREF_STORE (not streamed)
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bne len, rem, 1b
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ADD dst, dst, 4*NBYTES
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cleanup_src_unaligned:
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beqz len, done
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and rem, len, NBYTES-1 # rem = len % NBYTES
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beq rem, len, copy_bytes
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nop
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1:
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EXC( LDFIRST t0, FIRST(0)(src), l_exc)
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EXC( LDREST t0, REST(0)(src), l_exc_copy)
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ADD src, src, NBYTES
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SUB len, len, NBYTES
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STORE t0, 0(dst)
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bne len, rem, 1b
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ADD dst, dst, NBYTES
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copy_bytes_checklen:
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beqz len, done
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nop
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copy_bytes:
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/* 0 < len < NBYTES */
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#define COPY_BYTE(N) \
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EXC( lb t0, N(src), l_exc); \
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SUB len, len, 1; \
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beqz len, done; \
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sb t0, N(dst)
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COPY_BYTE(0)
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COPY_BYTE(1)
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#ifdef USE_DOUBLE
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COPY_BYTE(2)
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COPY_BYTE(3)
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COPY_BYTE(4)
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COPY_BYTE(5)
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#endif
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EXC( lb t0, NBYTES-2(src), l_exc)
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SUB len, len, 1
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jr ra
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sb t0, NBYTES-2(dst)
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done:
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jr ra
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nop
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END(__copy_user_inatomic)
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l_exc_copy:
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/*
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* Copy bytes from src until faulting load address (or until a
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* lb faults)
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*
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* When reached by a faulting LDFIRST/LDREST, THREAD_BUADDR($28)
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* may be more than a byte beyond the last address.
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* Hence, the lb below may get an exception.
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*
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* Assumes src < THREAD_BUADDR($28)
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*/
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LOAD t0, TI_TASK($28)
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nop
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LOAD t0, THREAD_BUADDR(t0)
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1:
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EXC( lb t1, 0(src), l_exc)
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ADD src, src, 1
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sb t1, 0(dst) # can't fault -- we're copy_from_user
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bne src, t0, 1b
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ADD dst, dst, 1
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l_exc:
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LOAD t0, TI_TASK($28)
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nop
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LOAD t0, THREAD_BUADDR(t0) # t0 is just past last good address
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nop
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SUB len, AT, t0 # len number of uncopied bytes
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jr ra
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nop
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