arch/arc/include/asm/checksum.h

Source file repositories/reference/linux-study-clean/arch/arc/include/asm/checksum.h

File Facts

System
Linux kernel
Corpus path
arch/arc/include/asm/checksum.h
Extension
.h
Size
2371 bytes
Lines
99
Domain
Architecture Layer
Bucket
arch/arc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#ifndef _ASM_ARC_CHECKSUM_H
#define _ASM_ARC_CHECKSUM_H

/*
 *	Fold a partial checksum
 *
 *  The 2 swords comprising the 32bit sum are added, any carry to 16th bit
 *  added back and final sword result inverted.
 */
static inline __sum16 csum_fold(__wsum s)
{
	unsigned int r = s << 16 | s >> 16;	/* ror */
	s = ~s;
	s -= r;
	return s >> 16;
}

/*
 *	This is a version of ip_compute_csum() optimized for IP headers,
 *	which always checksum on 4 octet boundaries.
 */
static inline __sum16
ip_fast_csum(const void *iph, unsigned int ihl)
{
	const void *ptr = iph;
	unsigned int tmp, tmp2, sum;

	__asm__(
	"	ld.ab  %0, [%3, 4]		\n"
	"	ld.ab  %2, [%3, 4]		\n"
	"	sub    %1, %4, 2		\n"
	"	lsr.f  lp_count, %1, 1		\n"
	"	bcc    0f			\n"
	"	add.f  %0, %0, %2		\n"
	"	ld.ab  %2, [%3, 4]		\n"
	"0:	lp     1f			\n"
	"	ld.ab  %1, [%3, 4]		\n"
	"	adc.f  %0, %0, %2		\n"
	"	ld.ab  %2, [%3, 4]		\n"
	"	adc.f  %0, %0, %1		\n"
	"1:	adc.f  %0, %0, %2		\n"
	"	add.cs %0,%0,1			\n"
	: "=&r"(sum), "=r"(tmp), "=&r"(tmp2), "+&r" (ptr)
	: "r"(ihl)
	: "cc", "lp_count", "memory");

	return csum_fold(sum);
}

/*
 * TCP pseudo Header is 12 bytes:
 * SA [4], DA [4], zeroes [1], Proto[1], TCP Seg(hdr+data) Len [2]
 */
static inline __wsum
csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
		   __u8 proto, __wsum sum)
{
	__asm__ __volatile__(
	"	add.f %0, %0, %1	\n"
	"	adc.f %0, %0, %2	\n"
	"	adc.f %0, %0, %3	\n"
	"	adc.f %0, %0, %4	\n"
	"	adc   %0, %0, 0		\n"
	: "+&r"(sum)
	: "r"(saddr), "r"(daddr),
#ifdef CONFIG_CPU_BIG_ENDIAN
	  "r"(len),
#else
	  "r"(len << 8),
#endif
	  "r"(htons(proto))
	: "cc");

	return sum;
}

#define csum_fold csum_fold
#define ip_fast_csum ip_fast_csum
#define csum_tcpudp_nofold csum_tcpudp_nofold

#include <asm-generic/checksum.h>

#endif /* _ASM_ARC_CHECKSUM_H */

Annotation

Implementation Notes