From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f53.google.com (mail-wm1-f53.google.com [209.85.128.53]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 90C904028D8 for ; Tue, 19 May 2026 14:00:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779199243; cv=none; b=H35PAuJsjqCCZcbMPHaCIZGbV4bMbhvPPjrfNQmapVkGAS5FT+wBgQjxYcOG2CpibxFo47Na5nqGxue3OfsQNkneqTmw8SOpeIM9AK6Bpq+w+YfBePgNJnqLTVOy6DEBgdyShWivvRokI3RG0xy0V0SPefItsgAo1jFOCa2cLfQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779199243; c=relaxed/simple; bh=n0E2lDML1l8mOysQKHNgZZUgw9bXTxT4damLfxTShgE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=M4H1iBkhKAYnIzXEIsr3CQKHAfsuBNCxzQ6jjyzmGKZtTPoyOeued5kObJUzeVzz7e2lbkR5Gw8dwII7uz+3e6tNEJ4FcGWt4N7awNxiyd/MmCnlkmQ7bUj/O0uJ/S7DkH52+wuiY9jMrcRqby6c1cVDr83j3v1X7wGBWysCxrk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=FoJ14Fnb; arc=none smtp.client-ip=209.85.128.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="FoJ14Fnb" Received: by mail-wm1-f53.google.com with SMTP id 5b1f17b1804b1-48fde648a71so26344755e9.0 for ; Tue, 19 May 2026 07:00:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1779199240; x=1779804040; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=y7GQ3Lzv1zsJ5so1gCOAqFSPiY4qAFEC2q/y3GviMUk=; b=FoJ14Fnb6uP2vXvotkokDrbEyZzvOnwHwjnzCpc+Z0ZO0nVoQB5tJRjMJ//4epFpIH W2fz4VR5V53oELoOHJVWauqYn2d+XSRc+S9Rn5beKUwbk7t3lxMYtbEtRXbbzhm/i86E ZxSVTbUHKSD1tw66IVZ0Kj9ULHIfm3m2JA4AurtZS3Oka0HBItIaNUG/L9jEgmOfQa3/ hetFOLEwyW0HXPV3nZZtl+hfDn66HrYNGy04E4Ttm1c3onoApK9w7MNxbC+OVqLr1GHN Okzjt5rT5psqi2Utl9k9FUR8NRk1SqK2oy8IiNCH94JJM3A+BAlKzKtdJO0zLLw4iUuT PMlQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779199240; x=1779804040; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=y7GQ3Lzv1zsJ5so1gCOAqFSPiY4qAFEC2q/y3GviMUk=; b=UWOhG1WkTe+fuAVW7XPFxPHrvC94a2L/cWQoOHO5SmEA0KxHku0tQuKHVdS7xxtFxM qJbxXP/bmQT8uATJNVjJm7biPZVGRwWgAZfP5OF4Vz/S3MpWCSnYrfgy9REQmHdCHWzZ MWDf1tpEygDXiZYsKiGGfe7G4c7d0giz+nr0W6BMbaTzKFc4YZJ5mzxm0/IJeqnAHYRZ +h6sht1szpcR8pTy8g+GtmE17FKuzNuuu9EvGpaDvsxdYt4EfQGZxtxZw1y/JVX2rJ9X BmpATqSSkTmr16RHfsUCECeqRcCI34FcfYgMrqWTfotkwNq9krpJrNlVxTnRUtMCz9e9 OORQ== X-Forwarded-Encrypted: i=1; AFNElJ+Q6dkQsjV74jCy2wM0stghErufzNiExQtvkzjDIYdoRn+7ta100qbUykiDCphvs1XpsKhjNVsGAzOyMcE=@vger.kernel.org X-Gm-Message-State: AOJu0YxdniQqnXZJ553KZj7QkbA2Q3b6yQHUGVuUHfVdEt4WW0JNeCXZ k8yUM9T7O2N4ArvC7Q8+TXQg7atlLsuq/JOn+yYQf2A6wjDZc4E3j0oW X-Gm-Gg: Acq92OGuL9iCwvgSFFrqhtJyqgu/ImO22TYgAYk4s67UAeFFrk3mEJPfvHbLne4m8Sf fx7Ph4DTo8gdCaukhBxJ72ZdwcdESqBWeV4liBUqpJ1W7bYSrWO00l2TkVh+wnPtSkoHHNxUsgO 9hHlRvP4YrTpSpVVfjaqBMEsFjKyEKiT/mty8/v562RkJacJzhvCuQM0JC/4O3xX4ct/hw93wJk 00tXe1l/4V1ZzQZlhvLILn5QIYoqt1yLcptj7OarMQdaG9qOMmgQyYeqSIiJY/XWshFRBuFDD6w v0XsfyLfTe+h+M62n52N+EUol1jrU/7xTO8W+ZU2y0lCKE9EVNbYd01x4JwXxxm1yH0Cvc6ZJi6 Oz+cBRfFr2BcQOeusyipklx3UIL1MiYKSBii7/ZuuPoJyYAuDps7GPQQOc3fPA1qMP9OVfUzHVu TlUrk+MMiH5Xel3ez2IUy//T1wdypbgHZOgU2KTRDnSliI6uSg3Lo= X-Received: by 2002:a05:600c:b55:b0:48a:5ee0:7781 with SMTP id 5b1f17b1804b1-48fd636ae2fmr272682745e9.16.1779199239456; Tue, 19 May 2026 07:00:39 -0700 (PDT) Received: from RTRKW671-LIN.domain.local ([95.86.49.225]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45d9e767d0bsm44065144f8f.3.2026.05.19.07.00.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 May 2026 07:00:39 -0700 (PDT) From: Milan Tripkovic To: pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, kees@kernel.org Cc: alex@ghiti.fr, andy@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Dusan.Stojkovic@rt-rk.com, Milan Tripkovic Subject: [PATCH v5 1/2] riscv: lib: add memcmp() implementation Date: Tue, 19 May 2026 16:00:28 +0200 Message-ID: <20260519140029.1190381-2-milant2002@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260519140029.1190381-1-milant2002@gmail.com> References: <20260519140029.1190381-1-milant2002@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Milan Tripkovic Add an assembly implementation of memcmp() for RISC-V. The implementation uses word-aligned loads for the generic path and the ZBB extension for optimized sign resolution, with an assembly fallback for non-ZBB systems. Benchmark results (QEMU TCG, rv64): Len | Default |NoALIGN | ALIGN | %NoALIGN | %ALIGN ------|---------|--------|--------|----------|-------- 1 B | 20.3 | 21.5 | 20.9 | +5.9% | +3.0% 7 B | 88.9 | 96.9 | 155.7 | +9.0% | +75.1% 8 B | 89.6 | 110.5 | 176.2 | +23.3% | +96.7% 16 B | 134.4 | 172.8 | 334.8 | +28.6% | +149.1% 31 B | 163.5 | 211.9 | 606.2 | +29.6% | +270.8% 64 B | 203.8 | 240.3 | 968.6 | +17.9% | +375.3% 127 B | 224.6 | 269.0 | 1362.8 | +19.8% | +506.8% 512 B | 235.7 | 269.9 | 1913.7 | +14.5% | +711.9% 1024 B| 256.8 | 283.5 | 2123.6 | +10.4% | +726.9% 4096 B| 263.8 | 299.7 | 2290.4 | +13.6% | +768.2% Signed-off-by: Milan Tripkovic --- v5 changes: - Optimized generic memcmp path with word-aligned loads. - Implemented non-ZBB fallback to byte comparison per review. - Link to v4: https://lore.kernel.org/all/20260518131407.1026049-2-milant2002@gmail.com/ v2 changes: - Added alignment checks for buffers to avoid expensive misaligned loads. - Optimized the loop using end-pointers to reduce per-iteration overhead. - Implemented word-aligned tail handling using ZBB shifts. - Removed redundant pointer equality (a0 == a1) check. - Retained BE support via #ifndef; ZBB rev8 is used for the LE fast-path. - Link to v1: https://lore.kernel.org/all/20260512141007.1193033-1-milant2002@gmail.com/ arch/riscv/include/asm/string.h | 2 + arch/riscv/lib/Makefile | 1 + arch/riscv/lib/memcmp.S | 106 ++++++++++++++++++++++++++++++++ arch/riscv/purgatory/Makefile | 5 +- 4 files changed, 113 insertions(+), 1 deletion(-) create mode 100644 arch/riscv/lib/memcmp.S diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h index 764ffe8f6..5c5299678 100644 --- a/arch/riscv/include/asm/string.h +++ b/arch/riscv/include/asm/string.h @@ -18,6 +18,8 @@ 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_MEMCMP +extern asmlinkage int memcmp(const void *, const void *, size_t); #if !(defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) #define __HAVE_ARCH_STRCMP diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile index 6f767b2a3..b529e1be1 100644 --- a/arch/riscv/lib/Makefile +++ b/arch/riscv/lib/Makefile @@ -3,6 +3,7 @@ lib-y += delay.o lib-y += memcpy.o lib-y += memset.o lib-y += memmove.o +lib-y += memcmp.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) lib-y += strcmp.o lib-y += strlen.o diff --git a/arch/riscv/lib/memcmp.S b/arch/riscv/lib/memcmp.S new file mode 100644 index 000000000..cb71cd5ae --- /dev/null +++ b/arch/riscv/lib/memcmp.S @@ -0,0 +1,106 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +#include +#include +#include +#include + +#if defined(CONFIG_RISCV_ISA_ZBB) && defined(CONFIG_TOOLCHAIN_HAS_ZBB) +.option push +.option arch,+zbb +#endif + +/* int memcmp(const void *cs, const void *ct, size_t n) */ +SYM_FUNC_START(memcmp) +/* + * Parameters + * a0 - Pointer to first memory block (cs), also return value + * a1 - Pointer to second memory block (ct) + * a2 - Number of bytes to compare (n), decremented during loop + * + * Returns + * a0 - 0 if equal, positive if cs > ct, negative if cs < ct + * + * Clobbers + * t0, t1, t2, t3, t4 + */ + add t3, a0, a2 + or t0, a0, a1 + andi t0, t0, (SZREG - 1) + bnez t0, 5f + + addi t4, t3, -SZREG + bltu t4, a0, 7f + +1: + REG_L t1, 0(a0) + REG_L t2, 0(a1) + bne t1, t2, 2f + addi a0, a0, SZREG + addi a1, a1, SZREG + bleu a0, t4, 1b + +#if defined(CONFIG_TOOLCHAIN_HAS_ZBB) +7: + __ALTERNATIVE_CFG("j 5f", "nop", 0, RISCV_ISA_EXT_ZBB, + IS_ENABLED(CONFIG_RISCV_ISA_ZBB)) + + beq a0, t3, 4f + REG_L t1, 0(a0) + REG_L t2, 0(a1) + + sub t0, t3, a0 + li t4, SZREG + sub t0, t4, t0 + slli t0, t0, 3 + +#ifndef CONFIG_CPU_BIG_ENDIAN + rev8 t1, t1 + rev8 t2, t2 +#endif + srl t1, t1, t0 + srl t2, t2, t0 + + bne t1, t2, 8f + li a0, 0 + ret +#else + j 5f +#endif +5: + beq a0, t3, 4f +6: + lbu t1, 0(a0) + lbu t2, 0(a1) + bne t1, t2, 3f + addi a0, a0, 1 + addi a1, a1, 1 + bne a0, t3, 6b + +4: li a0, 0 + ret +2: +#if !defined(CONFIG_CPU_BIG_ENDIAN) && defined(CONFIG_TOOLCHAIN_HAS_ZBB) + __ALTERNATIVE_CFG("j 5b", "nop", 0, RISCV_ISA_EXT_ZBB, IS_ENABLED(CONFIG_RISCV_ISA_ZBB)) + rev8 t1, t1 + rev8 t2, t2 +#elif !defined(CONFIG_CPU_BIG_ENDIAN) + j 5b +#endif +8: + sltu a0, t2, t1 + sltu t0, t1, t2 + sub a0, a0, t0 + ret + +3: + sub a0, t1, t2 + ret + +SYM_FUNC_END(memcmp) +SYM_FUNC_ALIAS(__pi_memcmp, memcmp) +EXPORT_SYMBOL(memcmp) + +#if defined(CONFIG_RISCV_ISA_ZBB) && defined(CONFIG_TOOLCHAIN_HAS_ZBB) +.option pop +#endif diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile index b0358a78f..456929971 100644 --- a/arch/riscv/purgatory/Makefile +++ b/arch/riscv/purgatory/Makefile @@ -1,6 +1,6 @@ # SPDX-License-Identifier: GPL-2.0 -purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o +purgatory-y := purgatory.o sha256.o entry.o string.o ctype.o memcpy.o memset.o memcmp.o ifeq ($(CONFIG_KASAN_GENERIC)$(CONFIG_KASAN_SW_TAGS),) purgatory-y += strcmp.o strlen.o strncmp.o strnlen.o strchr.o strrchr.o endif @@ -41,6 +41,9 @@ $(obj)/strchr.o: $(srctree)/arch/riscv/lib/strchr.S FORCE $(obj)/strrchr.o: $(srctree)/arch/riscv/lib/strrchr.S FORCE $(call if_changed_rule,as_o_S) +$(obj)/memcmp.o: $(srctree)/arch/riscv/lib/memcmp.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 -- 2.43.0