Add strnlen() implementation for RISC-V with both generic and Zbb-optimized versions, derived from strlen.S.
Signed-off-by: Feng Jiang <[email protected]> --- arch/riscv/include/asm/string.h | 3 + arch/riscv/lib/Makefile | 1 + arch/riscv/lib/strnlen.S | 164 ++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 5 +- 4 files changed, 172 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/lib/strnlen.S diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index 5ba77f60bf0b..16634d67c217 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -28,6 +28,9 @@ extern asmlinkage __kernel_size_t strlen(const char *); #define __HAVE_ARCH_STRNCMP extern asmlinkage int strncmp(const char *cs, const char *ct, size_t count); + +#define __HAVE_ARCH_STRNLEN +extern asmlinkage __kernel_size_t strnlen(const char *, size_t); #endif /* For those files which don't want to check by kasan. */ diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index bbc031124974..0969d8136df0 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -7,6 +7,7 @@ ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) lib-y += strcmp.o lib-y += strlen.o lib-y += strncmp.o +lib-y += strnlen.o endif lib-y += csum.o ifeq ($(CONFIG_MMU), y) diff --git a/arch/riscv/lib/strnlen.S b/arch/riscv/lib/strnlen.S new file mode 100644 index 000000000000..4af0df9442f1 --- /dev/null +++ b/arch/riscv/lib/strnlen.S @@ -0,0 +1,164 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/* + * Base on arch/riscv/lib/strlen.S + * + * Copyright (C) Feng Jiang <[email protected]> + */ + +#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. */ + bleu a1, a0, 3f + + 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. */ + bgeu a0, a1, 3f +2: + ret +3: + mv a0, a1 + ret + +.option pop +#endif +SYM_FUNC_END(strnlen) +SYM_FUNC_ALIAS(__pi_strnlen, strnlen) +EXPORT_SYMBOL(strnlen) diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index 530e497ca2f9..d7c0533108be 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -2,7 +2,7 @@ purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) -purgatory-y += strcmp.o strlen.o strncmp.o +purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o endif targets += $(purgatory-y) @@ -32,6 +32,9 @@ $(obj)/strncmp.o: $(srctree)/arch/riscv/lib/strncmp.S FORCE $(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE $(call if_changed_rule,cc_o_c) +$(obj)/strnlen.o: $(srctree)/arch/riscv/lib/strnlen.S FORCE + $(call if_changed_rule,as_o_S) + CFLAGS_sha256.o := -D__DISABLE_EXPORTS -D__NO_FORTIFY CFLAGS_string.o := -D__DISABLE_EXPORTS CFLAGS_ctype.o := -D__DISABLE_EXPORTS -- 2.25.1
