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Message-Id: <20260107023517.46840-6-jiangfeng@kylinos.cn> Date: Wed, 7 Jan 2026 10:35:17 +0800 From: Feng Jiang <jiangfeng@...inos.cn> To: pjw@...nel.org, palmer@...belt.com, aou@...s.berkeley.edu, alex@...ti.fr, kees@...nel.org, andy@...nel.org, jiangfeng@...inos.cn, ebiggers@...nel.org, martin.petersen@...cle.com, Jason@...c4.com, conor.dooley@...rochip.com, samuel.holland@...ive.com, charlie@...osinc.com, ajones@...tanamicro.com, nathan@...nel.org, linus.walleij@...aro.org Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: [PATCH 5/5] riscv: lib: add strrchr implementation Add a basic assembly implementation of strrchr() for RISC-V. This provides a functional byte-by-byte version as a foundation for future optimizations. Signed-off-by: Feng Jiang <jiangfeng@...inos.cn> --- arch/riscv/include/asm/string.h | 3 +++ arch/riscv/lib/Makefile | 1 + arch/riscv/lib/strrchr.S | 37 +++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 5 ++++- 4 files changed, 45 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/lib/strrchr.S diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index ca3ade82b124..764ffe8f6479 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -34,6 +34,9 @@ extern asmlinkage __kernel_size_t strnlen(const char *, size_t); #define __HAVE_ARCH_STRCHR extern asmlinkage char *strchr(const char *, int); + +#define __HAVE_ARCH_STRRCHR +extern asmlinkage char *strrchr(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 b7f804dce1c3..735d0b665536 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -9,6 +9,7 @@ lib-y += strlen.o lib-y += strncmp.o lib-y += strnlen.o lib-y += strchr.o +lib-y += strrchr.o endif lib-y += csum.o ifeq ($(CONFIG_MMU), y) diff --git a/arch/riscv/lib/strrchr.S b/arch/riscv/lib/strrchr.S new file mode 100644 index 000000000000..ac58b20ca21d --- /dev/null +++ b/arch/riscv/lib/strrchr.S @@ -0,0 +1,37 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/* + * Copyright (C) 2025 Feng Jiang <jiangfeng@...inos.cn> + */ + +#include <linux/linkage.h> +#include <asm/asm.h> + +/* char *strrchr(const char *s, int c) */ +SYM_FUNC_START(strrchr) + /* + * Parameters + * a0 - The string to be searched + * a1 - The character to seaerch for + * + * Returns + * a0 - Address of last occurrence of 'c' or 0 + * + * Clobbers + * t0, t1 + */ + andi a1, a1, 0xff + mv t1, a0 + li a0, 0 +1: + lbu t0, 0(t1) + bne t0, a1, 2f + mv a0, t1 +2: + addi t1, t1, 1 + bnez t0, 1b + ret +SYM_FUNC_END(strrchr) + +SYM_FUNC_ALIAS_WEAK(__pi_strrchr, strrchr) +EXPORT_SYMBOL(strrchr) diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index e7b3d748c913..b0358a78f11a 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -2,7 +2,7 @@ purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) -purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o strchr.o +purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o strchr.o strrchr.o endif targets += $(purgatory-y) @@ -38,6 +38,9 @@ $(obj)/strnlen.o: $(srctree)/arch/riscv/lib/strnlen.S FORCE $(obj)/strchr.o: $(srctree)/arch/riscv/lib/strchr.S FORCE $(call if_changed_rule,as_o_S) +$(obj)/strrchr.o: $(srctree)/arch/riscv/lib/strrchr.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
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