[PATCH 1/5] riscv: Checksum header

[Charlie Jenkins]

Provide checksum algorithms that have been designed to leverage riscv
instructions such as rotate. In 64-bit, can take advantage of the larger
register to avoid some overflow checking.

Add configuration for Zba extension and add march for Zba and Zbb.

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
 arch/riscv/Kconfig                | 23 +++++++++++
 arch/riscv/Makefile               |  2 +
 arch/riscv/include/asm/checksum.h | 86 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 111 insertions(+)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 4c07b9189c86..8d7e475ca28d 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -507,6 +507,29 @@ config RISCV_ISA_V_DEFAULT_ENABLE
 
 	  If you don't know what to do here, say Y.
 
+config TOOLCHAIN_HAS_ZBA
+	bool
+	default y
+	depends on !64BIT || $(cc-option,-mabi=lp64 -march=rv64ima_zba)
+	depends on !32BIT || $(cc-option,-mabi=ilp32 -march=rv32ima_zba)
+	depends on LLD_VERSION >= 150000 || LD_VERSION >= 23900
+	depends on AS_HAS_OPTION_ARCH
+
+config RISCV_ISA_ZBA
+	bool "Zba extension support for bit manipulation instructions"
+	depends on TOOLCHAIN_HAS_ZBA
+	depends on MMU
+	depends on RISCV_ALTERNATIVE
+	default y
+	help
+	   Adds support to dynamically detect the presence of the ZBA
+	   extension (basic bit manipulation) and enable its usage.
+
+	   The Zba extension provides instructions to accelerate a number
+	   of bit-specific address creation operations.
+
+	   If you don't know what to do here, say Y.
+
 config TOOLCHAIN_HAS_ZBB
 	bool
 	default y
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 6ec6d52a4180..51fa3f67fc9a 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -61,6 +61,8 @@ riscv-march-$(CONFIG_ARCH_RV64I)	:= rv64ima
 riscv-march-$(CONFIG_FPU)		:= $(riscv-march-y)fd
 riscv-march-$(CONFIG_RISCV_ISA_C)	:= $(riscv-march-y)c
 riscv-march-$(CONFIG_RISCV_ISA_V)	:= $(riscv-march-y)v
+riscv-march-$(CONFIG_RISCV_ISA_ZBA)	:= $(riscv-march-y)_zba
+riscv-march-$(CONFIG_RISCV_ISA_ZBB)	:= $(riscv-march-y)_zbb
 
 ifdef CONFIG_TOOLCHAIN_NEEDS_OLD_ISA_SPEC
 KBUILD_CFLAGS += -Wa,-misa-spec=2.2
diff --git a/arch/riscv/include/asm/checksum.h b/arch/riscv/include/asm/checksum.h
new file mode 100644
index 000000000000..cd98f8cde888
--- /dev/null
+++ b/arch/riscv/include/asm/checksum.h
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * IP checksum routines
+ *
+ * Copyright (C) 2023 Rivos Inc.
+ */
+#ifndef __ASM_RISCV_CHECKSUM_H
+#define __ASM_RISCV_CHECKSUM_H
+
+#include <linux/in6.h>
+#include <linux/uaccess.h>
+
+/* Default version is sufficient for 32 bit */
+#ifdef CONFIG_64BIT
+#define _HAVE_ARCH_IPV6_CSUM
+__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
+			const struct in6_addr *daddr,
+			__u32 len, __u8 proto, __wsum sum);
+#endif
+
+/*
+ *	Fold a partial checksum without adding pseudo headers
+ */
+static inline __sum16 csum_fold(__wsum sum)
+{
+	sum += (sum >> 16) | (sum << 16);
+	return (__force __sum16)(~(sum >> 16));
+}
+
+#define csum_fold csum_fold
+
+/*
+ *	This is a version of ip_compute_csum() optimized for IP headers,
+ *	which always checksum on 4 octet boundaries.
+ *	Optimized for 32 and 64 bit platforms, with and without vector, with and
+ *	without the bitmanip extensions zba/zbb.
+ */
+#ifdef CONFIG_32BIT
+static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
+{
+	__wsum csum = 0;
+	int pos = 0;
+
+	do {
+		csum += ((const __wsum *)iph)[pos];
+		csum += csum < ((const __wsum *)iph)[pos];
+	} while (++pos < ihl);
+	return csum_fold(csum);
+}
+#else
+
+/*
+ * Quickly compute an IP checksum with the assumption that IPv4 headers will
+ * always be in multiples of 32-bits, and have an ihl of at least 5.
+ * @ihl is the number of 32 bit segments and must be greater than or equal to 5.
+ * @iph is also assumed to be word aligned.
+ */
+static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
+{
+	unsigned long beginning;
+	unsigned long csum = 0;
+
+	beginning = ((const unsigned long *)iph)[0];
+	beginning += ((const unsigned long *)iph)[1];
+	beginning += beginning < ((const unsigned long *)iph)[1];
+	int pos = 4;
+
+	do {
+		csum += ((const unsigned int *)iph)[pos];
+	} while (++pos < ihl);
+	csum += beginning;
+	csum += csum < beginning;
+	csum += (csum >> 32) | (csum << 32); // Calculate overflow
+	return csum_fold((__force __wsum)(csum >> 32));
+}
+#endif
+#define ip_fast_csum ip_fast_csum
+
+#ifdef CONFIG_64BIT
+extern unsigned int do_csum(const unsigned char *buff, int len);
+#define do_csum do_csum
+#endif
+
+#include <asm-generic/checksum.h>
+
+#endif

-- 
2.41.0