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/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Base on arch/riscv/lib/strlen.S
*
* Copyright (C) Feng Jiang <jiangfeng@kylinos.cn>
*/
#include <linux/linkage.h>
#include <asm/asm.h>
#include <asm/alternative-macros.h>
#include <asm/hwcap.h>
/* size_t strnlen(const char *s, size_t count) */
SYM_FUNC_START(strnlen)
__ALTERNATIVE_CFG("nop", "j strnlen_zbb", 0, RISCV_ISA_EXT_ZBB,
IS_ENABLED(CONFIG_RISCV_ISA_ZBB) && IS_ENABLED(CONFIG_TOOLCHAIN_HAS_ZBB))
/*
* Returns
* a0 - String length
*
* Parameters
* a0 - String to measure
* a1 - Max length of string
*
* Clobbers
* t0, t1, t2
*/
addi t1, a0, -1
add t2, a0, a1
1:
addi t1, t1, 1
beq t1, t2, 2f
lbu t0, 0(t1)
bnez t0, 1b
2:
sub a0, t1, a0
ret
/*
* Variant of strnlen using the ZBB extension if available
*/
#if defined(CONFIG_RISCV_ISA_ZBB) && defined(CONFIG_TOOLCHAIN_HAS_ZBB)
strnlen_zbb:
#ifdef CONFIG_CPU_BIG_ENDIAN
# define CZ clz
# define SHIFT sll
#else
# define CZ ctz
# define SHIFT srl
#endif
.option push
.option arch,+zbb
/*
* Returns
* a0 - String length
*
* Parameters
* a0 - String to measure
* a1 - Max length of string
*
* Clobbers
* t0, t1, t2, t3, t4
*/
/* If maxlen is 0, return 0. */
beqz a1, 3f
/* Number of irrelevant bytes in the first word. */
andi t2, a0, SZREG-1
/* Align pointer. */
andi t0, a0, -SZREG
li t3, SZREG
sub t3, t3, t2
slli t2, t2, 3
/* Aligned boundary. */
add t4, a0, a1
andi t4, t4, -SZREG
/* Get the first word. */
REG_L t1, 0(t0)
/*
* Shift away the partial data we loaded to remove the irrelevant bytes
* preceding the string with the effect of adding NUL bytes at the
* end of the string's first word.
*/
SHIFT t1, t1, t2
/* Convert non-NUL into 0xff and NUL into 0x00. */
orc.b t1, t1
/* Convert non-NUL into 0x00 and NUL into 0xff. */
not t1, t1
/*
* Search for the first set bit (corresponding to a NUL byte in the
* original chunk).
*/
CZ t1, t1
/*
* The first chunk is special: compare against the number
* of valid bytes in this chunk.
*/
srli a0, t1, 3
/* Limit the result by maxlen. */
minu a0, a0, a1
bgtu t3, a0, 2f
/* Prepare for the word comparison loop. */
addi t2, t0, SZREG
li t3, -1
/*
* Our critical loop is 4 instructions and processes data in
* 4 byte or 8 byte chunks.
*/
.p2align 3
1:
REG_L t1, SZREG(t0)
addi t0, t0, SZREG
orc.b t1, t1
bgeu t0, t4, 4f
beq t1, t3, 1b
4:
not t1, t1
CZ t1, t1
srli t1, t1, 3
/* Get number of processed bytes. */
sub t2, t0, t2
/* Add number of characters in the first word. */
add a0, a0, t2
/* Add number of characters in the last word. */
add a0, a0, t1
/* Ensure the final result does not exceed maxlen. */
minu a0, a0, a1
2:
ret
3:
mv a0, a1
ret
.option pop
#endif
SYM_FUNC_END(strnlen)
SYM_FUNC_ALIAS(__pi_strnlen, strnlen)
EXPORT_SYMBOL(strnlen)
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