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Diffstat (limited to 'arch/riscv/lib/uaccess.S')
| -rw-r--r-- | arch/riscv/lib/uaccess.S | 237 |
1 files changed, 237 insertions, 0 deletions
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S new file mode 100644 index 000000000..09b47ebac --- /dev/null +++ b/arch/riscv/lib/uaccess.S @@ -0,0 +1,237 @@ +#include <linux/linkage.h> +#include <asm-generic/export.h> +#include <asm/asm.h> +#include <asm/asm-extable.h> +#include <asm/csr.h> + + .macro fixup op reg addr lbl +100: + \op \reg, \addr + _asm_extable 100b, \lbl + .endm + +ENTRY(__asm_copy_to_user) +ENTRY(__asm_copy_from_user) + + /* Enable access to user memory */ + li t6, SR_SUM + csrs CSR_STATUS, t6 + + /* + * Save the terminal address which will be used to compute the number + * of bytes copied in case of a fixup exception. + */ + add t5, a0, a2 + + /* + * Register allocation for code below: + * a0 - start of uncopied dst + * a1 - start of uncopied src + * a2 - size + * t0 - end of uncopied dst + */ + add t0, a0, a2 + + /* + * Use byte copy only if too small. + * SZREG holds 4 for RV32 and 8 for RV64 + */ + li a3, 9*SZREG /* size must be larger than size in word_copy */ + bltu a2, a3, .Lbyte_copy_tail + + /* + * Copy first bytes until dst is aligned to word boundary. + * a0 - start of dst + * t1 - start of aligned dst + */ + addi t1, a0, SZREG-1 + andi t1, t1, ~(SZREG-1) + /* dst is already aligned, skip */ + beq a0, t1, .Lskip_align_dst +1: + /* a5 - one byte for copying data */ + fixup lb a5, 0(a1), 10f + addi a1, a1, 1 /* src */ + fixup sb a5, 0(a0), 10f + addi a0, a0, 1 /* dst */ + bltu a0, t1, 1b /* t1 - start of aligned dst */ + +.Lskip_align_dst: + /* + * Now dst is aligned. + * Use shift-copy if src is misaligned. + * Use word-copy if both src and dst are aligned because + * can not use shift-copy which do not require shifting + */ + /* a1 - start of src */ + andi a3, a1, SZREG-1 + bnez a3, .Lshift_copy + +.Lword_copy: + /* + * Both src and dst are aligned, unrolled word copy + * + * a0 - start of aligned dst + * a1 - start of aligned src + * t0 - end of aligned dst + */ + addi t0, t0, -(8*SZREG) /* not to over run */ +2: + fixup REG_L a4, 0(a1), 10f + fixup REG_L a5, SZREG(a1), 10f + fixup REG_L a6, 2*SZREG(a1), 10f + fixup REG_L a7, 3*SZREG(a1), 10f + fixup REG_L t1, 4*SZREG(a1), 10f + fixup REG_L t2, 5*SZREG(a1), 10f + fixup REG_L t3, 6*SZREG(a1), 10f + fixup REG_L t4, 7*SZREG(a1), 10f + fixup REG_S a4, 0(a0), 10f + fixup REG_S a5, SZREG(a0), 10f + fixup REG_S a6, 2*SZREG(a0), 10f + fixup REG_S a7, 3*SZREG(a0), 10f + fixup REG_S t1, 4*SZREG(a0), 10f + fixup REG_S t2, 5*SZREG(a0), 10f + fixup REG_S t3, 6*SZREG(a0), 10f + fixup REG_S t4, 7*SZREG(a0), 10f + addi a0, a0, 8*SZREG + addi a1, a1, 8*SZREG + bltu a0, t0, 2b + + addi t0, t0, 8*SZREG /* revert to original value */ + j .Lbyte_copy_tail + +.Lshift_copy: + + /* + * Word copy with shifting. + * For misaligned copy we still perform aligned word copy, but + * we need to use the value fetched from the previous iteration and + * do some shifts. + * This is safe because reading is less than a word size. + * + * a0 - start of aligned dst + * a1 - start of src + * a3 - a1 & mask:(SZREG-1) + * t0 - end of uncopied dst + * t1 - end of aligned dst + */ + /* calculating aligned word boundary for dst */ + andi t1, t0, ~(SZREG-1) + /* Converting unaligned src to aligned src */ + andi a1, a1, ~(SZREG-1) + + /* + * Calculate shifts + * t3 - prev shift + * t4 - current shift + */ + slli t3, a3, 3 /* converting bytes in a3 to bits */ + li a5, SZREG*8 + sub t4, a5, t3 + + /* Load the first word to combine with second word */ + fixup REG_L a5, 0(a1), 10f + +3: + /* Main shifting copy + * + * a0 - start of aligned dst + * a1 - start of aligned src + * t1 - end of aligned dst + */ + + /* At least one iteration will be executed */ + srl a4, a5, t3 + fixup REG_L a5, SZREG(a1), 10f + addi a1, a1, SZREG + sll a2, a5, t4 + or a2, a2, a4 + fixup REG_S a2, 0(a0), 10f + addi a0, a0, SZREG + bltu a0, t1, 3b + + /* Revert src to original unaligned value */ + add a1, a1, a3 + +.Lbyte_copy_tail: + /* + * Byte copy anything left. + * + * a0 - start of remaining dst + * a1 - start of remaining src + * t0 - end of remaining dst + */ + bgeu a0, t0, .Lout_copy_user /* check if end of copy */ +4: + fixup lb a5, 0(a1), 10f + addi a1, a1, 1 /* src */ + fixup sb a5, 0(a0), 10f + addi a0, a0, 1 /* dst */ + bltu a0, t0, 4b /* t0 - end of dst */ + +.Lout_copy_user: + /* Disable access to user memory */ + csrc CSR_STATUS, t6 + li a0, 0 + ret + + /* Exception fixup code */ +10: + /* Disable access to user memory */ + csrc CSR_STATUS, t6 + sub a0, t5, a0 + ret +ENDPROC(__asm_copy_to_user) +ENDPROC(__asm_copy_from_user) +EXPORT_SYMBOL(__asm_copy_to_user) +EXPORT_SYMBOL(__asm_copy_from_user) + + +ENTRY(__clear_user) + + /* Enable access to user memory */ + li t6, SR_SUM + csrs CSR_STATUS, t6 + + add a3, a0, a1 + addi t0, a0, SZREG-1 + andi t1, a3, ~(SZREG-1) + andi t0, t0, ~(SZREG-1) + /* + * a3: terminal address of target region + * t0: lowest doubleword-aligned address in target region + * t1: highest doubleword-aligned address in target region + */ + bgeu t0, t1, 2f + bltu a0, t0, 4f +1: + fixup REG_S, zero, (a0), 11f + addi a0, a0, SZREG + bltu a0, t1, 1b +2: + bltu a0, a3, 5f + +3: + /* Disable access to user memory */ + csrc CSR_STATUS, t6 + li a0, 0 + ret +4: /* Edge case: unalignment */ + fixup sb, zero, (a0), 11f + addi a0, a0, 1 + bltu a0, t0, 4b + j 1b +5: /* Edge case: remainder */ + fixup sb, zero, (a0), 11f + addi a0, a0, 1 + bltu a0, a3, 5b + j 3b + + /* Exception fixup code */ +11: + /* Disable access to user memory */ + csrc CSR_STATUS, t6 + sub a0, a3, a0 + ret +ENDPROC(__clear_user) +EXPORT_SYMBOL(__clear_user) |