arch/x86/um/asm/checksum.h

Source file repositories/reference/linux-study-clean/arch/x86/um/asm/checksum.h

File Facts

System
Linux kernel
Corpus path
arch/x86/um/asm/checksum.h
Extension
.h
Size
3109 bytes
Lines
123
Domain
Architecture Layer
Bucket
arch/x86
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 __UM_CHECKSUM_H
#define __UM_CHECKSUM_H

#include <linux/string.h>
#include <linux/in6.h>
#include <linux/uaccess.h>

/*
 * computes the checksum of a memory block at buff, length len,
 * and adds in "sum" (32-bit)
 *
 * returns a 32-bit number suitable for feeding into itself
 * or csum_tcpudp_magic
 *
 * this function must be called with even lengths, except
 * for the last fragment, which may be odd
 *
 * it's best to have buff aligned on a 32-bit boundary
 */
extern __wsum csum_partial(const void *buff, int len, __wsum sum);

/* Do not call this directly. Declared for export type visibility. */
extern __visible __wsum csum_partial_copy_generic(const void *src, void *dst, int len);

/**
 * csum_fold - Fold and invert a 32bit checksum.
 * sum: 32bit unfolded sum
 *
 * Fold a 32bit running checksum to 16bit and invert it. This is usually
 * the last step before putting a checksum into a packet.
 * Make sure not to mix with 64bit checksums.
 */
static inline __sum16 csum_fold(__wsum sum)
{
	__asm__(
		"  addl %1,%0\n"
		"  adcl $0xffff,%0"
		: "=r" (sum)
		: "r" ((__force u32)sum << 16),
		  "0" ((__force u32)sum & 0xffff0000)
	);
	return (__force __sum16)(~(__force u32)sum >> 16);
}

/**
 * csum_tcpup_nofold - Compute an IPv4 pseudo header checksum.
 * @saddr: source address
 * @daddr: destination address
 * @len: length of packet
 * @proto: ip protocol of packet
 * @sum: initial sum to be added in (32bit unfolded)
 *
 * Returns the pseudo header checksum the input data. Result is
 * 32bit unfolded.
 */
static inline __wsum
csum_tcpudp_nofold(__be32 saddr, __be32 daddr, __u32 len,
		  __u8 proto, __wsum sum)
{
	asm("  addl %1, %0\n"
	    "  adcl %2, %0\n"
	    "  adcl %3, %0\n"
	    "  adcl $0, %0\n"
		: "=r" (sum)
	    : "g" (daddr), "g" (saddr), "g" ((len + proto) << 8), "0" (sum));
	return sum;
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
					__u32 len, __u8 proto,
					__wsum sum)
{
	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
}

/**
 * ip_fast_csum - Compute the IPv4 header checksum efficiently.
 * iph: ipv4 header
 * ihl: length of header / 4
 */
static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
	unsigned int sum;

	asm(	"  movl (%1), %0\n"
		"  subl $4, %2\n"

Annotation

Implementation Notes