Add a basic assembly implementation of strchr() for RISC-V. This provides a functional byte-by-byte version as a foundation for future optimizations.
Signed-off-by: Feng Jiang <[email protected]> --- arch/riscv/include/asm/string.h | 3 +++ arch/riscv/lib/Makefile | 1 + arch/riscv/lib/strchr.S | 35 +++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 5 ++++- 4 files changed, 43 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/lib/strchr.S diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index 16634d67c217..ca3ade82b124 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -31,6 +31,9 @@ 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); + +#define __HAVE_ARCH_STRCHR +extern asmlinkage char *strchr(const char *, int); #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 0969d8136df0..b7f804dce1c3 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -8,6 +8,7 @@ lib-y += strcmp.o lib-y += strlen.o lib-y += strncmp.o lib-y += strnlen.o +lib-y += strchr.o endif lib-y += csum.o ifeq ($(CONFIG_MMU), y) diff --git a/arch/riscv/lib/strchr.S b/arch/riscv/lib/strchr.S new file mode 100644 index 000000000000..48c3a9da53e3 --- /dev/null +++ b/arch/riscv/lib/strchr.S @@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/* + * Copyright (C) 2025 Feng Jiang <[email protected]> + */ + +#include <linux/linkage.h> +#include <asm/asm.h> + +/* char *strchr(const char *s, int c) */ +SYM_FUNC_START(strchr) + /* + * Parameters + * a0 - The string to be searched + * a1 - The character to search for + * + * Returns + * a0 - Address of first occurrence of 'c' or 0 + * + * Clobbers + * t0 + */ + andi a1, a1, 0xff +1: + lbu t0, 0(a0) + beq t0, a1, 2f + addi a0, a0, 1 + bnez t0, 1b + li a0, 0 +2: + ret +SYM_FUNC_END(strchr) + +SYM_FUNC_ALIAS_WEAK(__pi_strchr, strchr) +EXPORT_SYMBOL(strchr) diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index d7c0533108be..e7b3d748c913 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -2,7 +2,7 @@ purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) -purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o +purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o strchr.o endif targets += $(purgatory-y) @@ -35,6 +35,9 @@ $(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE $(obj)/strnlen.o: $(srctree)/arch/riscv/lib/strnlen.S FORCE $(call if_changed_rule,as_o_S) +$(obj)/strchr.o: $(srctree)/arch/riscv/lib/strchr.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
