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ea196c548c
Fixing typos and grammar mistakes and using more intuitive label
name.
Signed-off-by: Akira Tsukamoto <akira.tsukamoto@gmail.com>
Fixes: ca6eaaa210 ("riscv: __asm_copy_to-from_user: Optimize unaligned memory access and pipeline stall")
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
236 lines
5.1 KiB
ArmAsm
236 lines
5.1 KiB
ArmAsm
#include <linux/linkage.h>
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#include <asm-generic/export.h>
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#include <asm/asm.h>
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#include <asm/csr.h>
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.macro fixup op reg addr lbl
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100:
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\op \reg, \addr
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.section __ex_table,"a"
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.balign RISCV_SZPTR
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RISCV_PTR 100b, \lbl
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.previous
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.endm
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ENTRY(__asm_copy_to_user)
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ENTRY(__asm_copy_from_user)
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/* Enable access to user memory */
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li t6, SR_SUM
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csrs CSR_STATUS, t6
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/* Save for return value */
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mv t5, a2
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/*
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* Register allocation for code below:
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* a0 - start of uncopied dst
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* a1 - start of uncopied src
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* a2 - size
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* t0 - end of uncopied dst
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*/
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add t0, a0, a2
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/*
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* Use byte copy only if too small.
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* SZREG holds 4 for RV32 and 8 for RV64
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*/
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li a3, 9*SZREG /* size must be larger than size in word_copy */
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bltu a2, a3, .Lbyte_copy_tail
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/*
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* Copy first bytes until dst is aligned to word boundary.
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* a0 - start of dst
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* t1 - start of aligned dst
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*/
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addi t1, a0, SZREG-1
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andi t1, t1, ~(SZREG-1)
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/* dst is already aligned, skip */
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beq a0, t1, .Lskip_align_dst
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1:
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/* a5 - one byte for copying data */
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fixup lb a5, 0(a1), 10f
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addi a1, a1, 1 /* src */
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fixup sb a5, 0(a0), 10f
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addi a0, a0, 1 /* dst */
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bltu a0, t1, 1b /* t1 - start of aligned dst */
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.Lskip_align_dst:
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/*
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* Now dst is aligned.
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* Use shift-copy if src is misaligned.
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* Use word-copy if both src and dst are aligned because
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* can not use shift-copy which do not require shifting
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*/
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/* a1 - start of src */
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andi a3, a1, SZREG-1
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bnez a3, .Lshift_copy
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.Lword_copy:
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/*
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* Both src and dst are aligned, unrolled word copy
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*
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* a0 - start of aligned dst
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* a1 - start of aligned src
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* t0 - end of aligned dst
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*/
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addi t0, t0, -(8*SZREG) /* not to over run */
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2:
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fixup REG_L a4, 0(a1), 10f
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fixup REG_L a5, SZREG(a1), 10f
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fixup REG_L a6, 2*SZREG(a1), 10f
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fixup REG_L a7, 3*SZREG(a1), 10f
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fixup REG_L t1, 4*SZREG(a1), 10f
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fixup REG_L t2, 5*SZREG(a1), 10f
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fixup REG_L t3, 6*SZREG(a1), 10f
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fixup REG_L t4, 7*SZREG(a1), 10f
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fixup REG_S a4, 0(a0), 10f
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fixup REG_S a5, SZREG(a0), 10f
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fixup REG_S a6, 2*SZREG(a0), 10f
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fixup REG_S a7, 3*SZREG(a0), 10f
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fixup REG_S t1, 4*SZREG(a0), 10f
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fixup REG_S t2, 5*SZREG(a0), 10f
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fixup REG_S t3, 6*SZREG(a0), 10f
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fixup REG_S t4, 7*SZREG(a0), 10f
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addi a0, a0, 8*SZREG
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addi a1, a1, 8*SZREG
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bltu a0, t0, 2b
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addi t0, t0, 8*SZREG /* revert to original value */
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j .Lbyte_copy_tail
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.Lshift_copy:
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/*
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* Word copy with shifting.
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* For misaligned copy we still perform aligned word copy, but
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* we need to use the value fetched from the previous iteration and
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* do some shifts.
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* This is safe because reading is less than a word size.
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*
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* a0 - start of aligned dst
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* a1 - start of src
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* a3 - a1 & mask:(SZREG-1)
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* t0 - end of uncopied dst
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* t1 - end of aligned dst
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*/
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/* calculating aligned word boundary for dst */
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andi t1, t0, ~(SZREG-1)
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/* Converting unaligned src to aligned src */
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andi a1, a1, ~(SZREG-1)
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/*
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* Calculate shifts
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* t3 - prev shift
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* t4 - current shift
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*/
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slli t3, a3, 3 /* converting bytes in a3 to bits */
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li a5, SZREG*8
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sub t4, a5, t3
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/* Load the first word to combine with second word */
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fixup REG_L a5, 0(a1), 10f
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3:
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/* Main shifting copy
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*
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* a0 - start of aligned dst
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* a1 - start of aligned src
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* t1 - end of aligned dst
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*/
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/* At least one iteration will be executed */
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srl a4, a5, t3
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fixup REG_L a5, SZREG(a1), 10f
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addi a1, a1, SZREG
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sll a2, a5, t4
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or a2, a2, a4
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fixup REG_S a2, 0(a0), 10f
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addi a0, a0, SZREG
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bltu a0, t1, 3b
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/* Revert src to original unaligned value */
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add a1, a1, a3
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.Lbyte_copy_tail:
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/*
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* Byte copy anything left.
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*
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* a0 - start of remaining dst
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* a1 - start of remaining src
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* t0 - end of remaining dst
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*/
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bgeu a0, t0, .Lout_copy_user /* check if end of copy */
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4:
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fixup lb a5, 0(a1), 10f
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addi a1, a1, 1 /* src */
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fixup sb a5, 0(a0), 10f
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addi a0, a0, 1 /* dst */
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bltu a0, t0, 4b /* t0 - end of dst */
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.Lout_copy_user:
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/* Disable access to user memory */
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csrc CSR_STATUS, t6
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li a0, 0
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ret
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ENDPROC(__asm_copy_to_user)
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ENDPROC(__asm_copy_from_user)
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EXPORT_SYMBOL(__asm_copy_to_user)
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EXPORT_SYMBOL(__asm_copy_from_user)
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ENTRY(__clear_user)
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/* Enable access to user memory */
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li t6, SR_SUM
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csrs CSR_STATUS, t6
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add a3, a0, a1
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addi t0, a0, SZREG-1
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andi t1, a3, ~(SZREG-1)
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andi t0, t0, ~(SZREG-1)
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/*
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* a3: terminal address of target region
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* t0: lowest doubleword-aligned address in target region
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* t1: highest doubleword-aligned address in target region
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*/
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bgeu t0, t1, 2f
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bltu a0, t0, 4f
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1:
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fixup REG_S, zero, (a0), 11f
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addi a0, a0, SZREG
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bltu a0, t1, 1b
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2:
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bltu a0, a3, 5f
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3:
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/* Disable access to user memory */
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csrc CSR_STATUS, t6
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li a0, 0
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ret
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4: /* Edge case: unalignment */
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fixup sb, zero, (a0), 11f
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addi a0, a0, 1
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bltu a0, t0, 4b
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j 1b
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5: /* Edge case: remainder */
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fixup sb, zero, (a0), 11f
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addi a0, a0, 1
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bltu a0, a3, 5b
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j 3b
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ENDPROC(__clear_user)
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EXPORT_SYMBOL(__clear_user)
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.section .fixup,"ax"
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.balign 4
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/* Fixup code for __copy_user(10) and __clear_user(11) */
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10:
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/* Disable access to user memory */
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csrs CSR_STATUS, t6
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mv a0, t5
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ret
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11:
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csrs CSR_STATUS, t6
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mv a0, a1
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ret
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.previous
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