From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6537FC54EBC for ; Thu, 12 Jan 2023 16:05:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ESr7rfDY8a/B3cow0MUgfBP44hfy49jNwsP/1RTcVCg=; b=GZ+Kg0rXc/Njq+ yP6ePepMCiwxElJ8GFW7lsX4PDV5NAECsexrafzj7D+uizvVEFMqBD0Lut99bvJQg6c2GY2Y01t41 ItApJWr15WU3SsKj4rGn8prpxLV0WKluuivYLOxHT81g9gUwByaWOYvHY6klaTyza7wn4mti7JR9s zlGoKmRUjTHsjNaza3K6KQ/SJDPM0OoteJk8B+ZH3ilCZGKnTjfA39wxAOTBBdrkZ6j7SN0RVQvWK MraNvBGVdOl0tx8c5q8XxYGmuu03p3pNaFMCHAgntBB3wHuIbLvr0XxMWklYHuC6ADMeilJm3KbwH VeiTJmK9Io5RuXusJV4g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1pG052-00Fnku-6G; Thu, 12 Jan 2023 16:05:28 +0000 Received: from gloria.sntech.de ([185.11.138.130]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1pG04y-00Fnjf-8X for linux-riscv@lists.infradead.org; Thu, 12 Jan 2023 16:05:26 +0000 Received: from ip5b412258.dynamic.kabel-deutschland.de ([91.65.34.88] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1pG04u-0000Ku-6j; Thu, 12 Jan 2023 17:05:20 +0100 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Andrew Jones Cc: linux-riscv@lists.infradead.org, palmer@dabbelt.com, christoph.muellner@vrull.eu, conor@kernel.org, philipp.tomsich@vrull.eu, jszhang@kernel.org Subject: Re: [PATCH v4 4/5] RISC-V: add infrastructure to allow different str* implementations Date: Thu, 12 Jan 2023 17:05:19 +0100 Message-ID: <2094019.QZUTf85G27@diego> In-Reply-To: <20230110121320.zr4tk4nl2w57klqg@orel> References: <20230109181755.2383085-1-heiko@sntech.de> <20230109181755.2383085-5-heiko@sntech.de> <20230110121320.zr4tk4nl2w57klqg@orel> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230112_080524_482015_5568D84D X-CRM114-Status: GOOD ( 35.39 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Hi Andrew, thanks a lot for taking the time to provide these extensive and really helpful comments. Am Dienstag, 10. Januar 2023, 13:13:20 CET schrieb Andrew Jones: > On Mon, Jan 09, 2023 at 07:17:54PM +0100, Heiko Stuebner wrote: > > From: Heiko Stuebner > > > > Depending on supported extensions on specific RISC-V cores, > > optimized str* functions might make sense. > > > > This adds basic infrastructure to allow patching the function calls > > via alternatives later on. > > > > The Linux kernel provides standard implementations for string functions > > but when architectures want to extend them, they need to provide their > > own. > > > > The added generic string functions are done in assembler (taken from > > disassembling the main-kernel functions for now) to allow us to control > > the used registers and extend them with optimized variants. > > > > Signed-off-by: Heiko Stuebner > > --- > > arch/riscv/include/asm/string.h | 10 +++++++++ > > arch/riscv/kernel/riscv_ksyms.c | 3 +++ > > arch/riscv/lib/Makefile | 3 +++ > > arch/riscv/lib/strcmp.S | 37 ++++++++++++++++++++++++++++++ > > arch/riscv/lib/strlen.S | 28 +++++++++++++++++++++++ > > arch/riscv/lib/strncmp.S | 40 +++++++++++++++++++++++++++++++++ > > arch/riscv/purgatory/Makefile | 13 +++++++++++ > > 7 files changed, 134 insertions(+) > > create mode 100644 arch/riscv/lib/strcmp.S > > create mode 100644 arch/riscv/lib/strlen.S > > create mode 100644 arch/riscv/lib/strncmp.S > > > > diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h > > index 909049366555..a96b1fea24fe 100644 > > --- a/arch/riscv/include/asm/string.h > > +++ b/arch/riscv/include/asm/string.h > > @@ -18,6 +18,16 @@ extern asmlinkage void *__memcpy(void *, const void *, size_t); > > #define __HAVE_ARCH_MEMMOVE > > extern asmlinkage void *memmove(void *, const void *, size_t); > > extern asmlinkage void *__memmove(void *, const void *, size_t); > > + > > +#define __HAVE_ARCH_STRCMP > > +extern asmlinkage int strcmp(const char *cs, const char *ct); > > + > > +#define __HAVE_ARCH_STRLEN > > +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); > > + > > /* For those files which don't want to check by kasan. */ > > #if defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__) > > #define memcpy(dst, src, len) __memcpy(dst, src, len) > > diff --git a/arch/riscv/kernel/riscv_ksyms.c b/arch/riscv/kernel/riscv_ksyms.c > > index 5ab1c7e1a6ed..a72879b4249a 100644 > > --- a/arch/riscv/kernel/riscv_ksyms.c > > +++ b/arch/riscv/kernel/riscv_ksyms.c > > @@ -12,6 +12,9 @@ > > EXPORT_SYMBOL(memset); > > EXPORT_SYMBOL(memcpy); > > EXPORT_SYMBOL(memmove); > > +EXPORT_SYMBOL(strcmp); > > +EXPORT_SYMBOL(strlen); > > +EXPORT_SYMBOL(strncmp); > > EXPORT_SYMBOL(__memset); > > EXPORT_SYMBOL(__memcpy); > > EXPORT_SYMBOL(__memmove); > > diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile > > index 25d5c9664e57..6c74b0bedd60 100644 > > --- a/arch/riscv/lib/Makefile > > +++ b/arch/riscv/lib/Makefile > > @@ -3,6 +3,9 @@ lib-y += delay.o > > lib-y += memcpy.o > > lib-y += memset.o > > lib-y += memmove.o > > +lib-y += strcmp.o > > +lib-y += strlen.o > > +lib-y += strncmp.o > > lib-$(CONFIG_MMU) += uaccess.o > > lib-$(CONFIG_64BIT) += tishift.o > > > > diff --git a/arch/riscv/lib/strcmp.S b/arch/riscv/lib/strcmp.S > > new file mode 100644 > > index 000000000000..94440fb8390c > > --- /dev/null > > +++ b/arch/riscv/lib/strcmp.S > > @@ -0,0 +1,37 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > + > > +#include > > +#include > > +#include > > + > > +/* int strcmp(const char *cs, const char *ct) */ > > +SYM_FUNC_START(strcmp) > > + /* > > + * Returns > > + * a0 - comparison result, value like strcmp > > + * > > + * Parameters > > + * a0 - string1 > > + * a1 - string2 > > + * > > + * Clobbers > > + * t0, t1, t2 > > + */ > > + mv t2, a1 > > The above instruction and the 'mv a1, t2' below appear to be attempting > to preserve a1, but that shouldn't be necessary. correct and gone now > > +1: > > + lbu t1, 0(a0) > > + lbu t0, 0(a1) > > I'd rather have t0 be 0(a0) and t1 be 0(a1) ok > > + addi a0, a0, 1 > > + addi a1, a1, 1 > > + beq t1, t0, 3f > > + li a0, 1 > > + bgeu t1, t0, 2f > > + li a0, -1 > > +2: > > + mv a1, t2 > > + ret > > +3: > > + bnez t1, 1b > > + li a0, 0 > > + j 2b > > For fun I removed one conditional and one unconditional branch (untested) > > 1: > lbu t0, 0(a0) > lbu t1, 0(a1) > addi a0, a0, 1 > addi a1, a1, 1 > bne t0, t1, 2f > bnez t0, 1b > li a0, 0 > ret > 2: > slt a1, t1, t0 > slli a1, a1, 1 > li a0, -1 > add a0, a0, a1 > ret yep that - looks correct - and also seems to produce correct results also including your sub a0, t0, t1 comment from the followup that then produces the same result als the zbb-variant. And I've also verified the - 0, if the s1 and s2 are equal; - a negative value if s1 is less than s2; - a positive value if s1 is greater than s2. return value calling convention with documentation And added a comment above it, pointing out this fact for the next person stumbling over this :-) > > +SYM_FUNC_END(strcmp) > > diff --git a/arch/riscv/lib/strlen.S b/arch/riscv/lib/strlen.S > > new file mode 100644 > > index 000000000000..09a7aaff26c8 > > --- /dev/null > > +++ b/arch/riscv/lib/strlen.S > > @@ -0,0 +1,28 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > + > > +#include > > +#include > > +#include > > + > > +/* int strlen(const char *s) */ > > +SYM_FUNC_START(strlen) > > + /* > > + * Returns > > + * a0 - string length > > + * > > + * Parameters > > + * a0 - String to measure > > + * > > + * Clobbers: > > + * t0, t1 > > + */ > > + mv t1, a0 > > +1: > > + lbu t0, 0(t1) > > + bnez t0, 2f > > + sub a0, t1, a0 > > + ret > > +2: > > + addi t1, t1, 1 > > + j 1b > > Slightly reorganizing looks better (to me) > > mv t1, a0 > 1: > lbu t0, 0(t1) > beqz t0, 2f > addi t1, t1, 1 > j 1b > 2: > sub a0, t1, a0 > ret ok > > +SYM_FUNC_END(strlen) > > diff --git a/arch/riscv/lib/strncmp.S b/arch/riscv/lib/strncmp.S > > new file mode 100644 > > index 000000000000..493ab6febcb2 > > --- /dev/null > > +++ b/arch/riscv/lib/strncmp.S > > @@ -0,0 +1,40 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > + > > +#include > > +#include > > +#include > > + > > +/* int strncmp(const char *cs, const char *ct, size_t count) */ > > +SYM_FUNC_START(strncmp) > > + /* > > + * Returns > > + * a0 - comparison result, value like strncmp > > + * > > + * Parameters > > + * a0 - string1 > > + * a1 - string2 > > + * a2 - number of characters to compare > > + * > > + * Clobbers > > + * t0, t1, t2 > > + */ > > + li t0, 0 > > +1: > > + beq a2, t0, 4f > > + add t1, a0, t0 > > + add t2, a1, t0 > > + lbu t1, 0(t1) > > + lbu t2, 0(t2) > > + beq t1, t2, 3f > > + li a0, 1 > > + bgeu t1, t2, 2f > > + li a0, -1 > > +2: > > + ret > > +3: > > + addi t0, t0, 1 > > + bnez t1, 1b > > +4: > > + li a0, 0 > > + j 2b > > (untested) > > li t2, 0 > 1: > beq a2, t2, 2f > lbu t0, 0(a0) > lbu t1, 0(a1) > addi a0, a0, 1 > addi a1, a1, 1 > bne t0, t1, 3f > addi t2, t2, 1 > bnez t0, 1b > 2: > li a0, 0 > ret > 3: > slt a1, t1, t0 > slli a1, a1, 1 > li a0, -1 > add a0, a0, a1 > ret same here, I did go over the changed assembly and verified that it produces the same results as the original and then did a second pass to also add the sub a0, t0, t1 replacment. > > +SYM_FUNC_END(strncmp) > > diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile > > index dd58e1d99397..d16bf715a586 100644 > > --- a/arch/riscv/purgatory/Makefile > > +++ b/arch/riscv/purgatory/Makefile > > @@ -2,6 +2,7 @@ > > OBJECT_FILES_NON_STANDARD := y > > > > purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o > > +purgatory-y += strcmp.o strlen.o strncmp.o > > > > targets += $(purgatory-y) > > PURGATORY_OBJS = $(addprefix $(obj)/,$(purgatory-y)) > > @@ -18,6 +19,15 @@ $(obj)/memcpy.o: $(srctree)/arch/riscv/lib/memcpy.S FORCE > > $(obj)/memset.o: $(srctree)/arch/riscv/lib/memset.S FORCE > > $(call if_changed_rule,as_o_S) > > > > +$(obj)/strcmp.o: $(srctree)/arch/riscv/lib/strcmp.S FORCE > > + $(call if_changed_rule,as_o_S) > > + > > +$(obj)/strlen.o: $(srctree)/arch/riscv/lib/strlen.S FORCE > > + $(call if_changed_rule,as_o_S) > > + > > +$(obj)/strncmp.o: $(srctree)/arch/riscv/lib/strncmp.S FORCE > > + $(call if_changed_rule,as_o_S) > > + > > $(obj)/sha256.o: $(srctree)/lib/crypto/sha256.c FORCE > > $(call if_changed_rule,cc_o_c) > > > > @@ -77,6 +87,9 @@ CFLAGS_ctype.o += $(PURGATORY_CFLAGS) > > AFLAGS_REMOVE_entry.o += -Wa,-gdwarf-2 > > AFLAGS_REMOVE_memcpy.o += -Wa,-gdwarf-2 > > AFLAGS_REMOVE_memset.o += -Wa,-gdwarf-2 > > +AFLAGS_REMOVE_strcmp.o += -Wa,-gdwarf-2 > > +AFLAGS_REMOVE_strlen.o += -Wa,-gdwarf-2 > > +AFLAGS_REMOVE_strncmp.o += -Wa,-gdwarf-2 > > > > $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE > > $(call if_changed,ld) > > > > With at least the removal of the unnecessary preserving of a1 in strcmp, > then it looks correct to me, so > > Reviewed-by: Andrew Jones > > But I think there's room for making it more readable, and maybe even > optimized, as I've tried to do. Thanks a lot Heiko _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv