arch/arm/include/asm/checksum.h

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

File Facts

System
Linux kernel
Corpus path
arch/arm/include/asm/checksum.h
Extension
.h
Size
4053 bytes
Lines
167
Domain
Architecture Layer
Bucket
arch/arm
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_ARM_CHECKSUM_H
#define __ASM_ARM_CHECKSUM_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
 */
__wsum csum_partial(const void *buff, int len, __wsum sum);

/*
 * the same as csum_partial, but copies from src while it
 * checksums, and handles user-space pointer exceptions correctly, when needed.
 *
 * here even more important to align src and dst on a 32-bit (or even
 * better 64-bit) boundary
 */

__wsum
csum_partial_copy_nocheck(const void *src, void *dst, int len);

__wsum
csum_partial_copy_from_user(const void __user *src, void *dst, int len);

#define _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
#define _HAVE_ARCH_CSUM_AND_COPY
static inline
__wsum csum_and_copy_from_user(const void __user *src, void *dst, int len)
{
	if (!access_ok(src, len))
		return 0;

	return csum_partial_copy_from_user(src, dst, len);
}

/*
 * 	Fold a partial checksum without adding pseudo headers
 */
static inline __sum16 csum_fold(__wsum sum)
{
	__asm__(
	"add	%0, %1, %1, ror #16	@ csum_fold"
	: "=r" (sum)
	: "r" (sum)
	: "cc");
	return (__force __sum16)(~(__force u32)sum >> 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)
{
	unsigned int tmp1;
	__wsum sum;

	__asm__ __volatile__(
	"ldr	%0, [%1], #4		@ ip_fast_csum		\n\
	ldr	%3, [%1], #4					\n\
	sub	%2, %2, #5					\n\
	adds	%0, %0, %3					\n\
	ldr	%3, [%1], #4					\n\
	adcs	%0, %0, %3					\n\
	ldr	%3, [%1], #4					\n\
1:	adcs	%0, %0, %3					\n\
	ldr	%3, [%1], #4					\n\
	tst	%2, #15			@ do this carefully	\n\
	subne	%2, %2, #1		@ without destroying	\n\
	bne	1b			@ the carry flag	\n\
	adcs	%0, %0, %3					\n\
	adc	%0, %0, #0"
	: "=r" (sum), "=r" (iph), "=r" (ihl), "=r" (tmp1)
	: "1" (iph), "2" (ihl)
	: "cc", "memory");
	return csum_fold(sum);
}

static inline __wsum

Annotation

Implementation Notes