arch/xtensa/include/asm/checksum.h

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

File Facts

System
Linux kernel
Corpus path
arch/xtensa/include/asm/checksum.h
Extension
.h
Size
5893 bytes
Lines
248
Domain
Architecture Layer
Bucket
arch/xtensa
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 _XTENSA_CHECKSUM_H
#define _XTENSA_CHECKSUM_H

#include <linux/in6.h>
#include <linux/uaccess.h>
#include <asm/core.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
 */
asmlinkage __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
 */

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

#define _HAVE_ARCH_CSUM_AND_COPY
/*
 *	Note: when you get a NULL pointer exception here this means someone
 *	passed in an incorrect kernel address to one of these functions.
 */
static inline
__wsum csum_partial_copy_nocheck(const void *src, void *dst, int len)
{
	return csum_partial_copy_generic(src, dst, len);
}

#define _HAVE_ARCH_COPY_AND_CSUM_FROM_USER
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_generic((__force const void *)src, dst, len);
}

/*
 *	Fold a partial checksum
 */

static __inline__ __sum16 csum_fold(__wsum sum)
{
	unsigned int __dummy;
	__asm__("extui	%1, %0, 16, 16\n\t"
		"extui	%0 ,%0, 0, 16\n\t"
		"add	%0, %0, %1\n\t"
		"slli	%1, %0, 16\n\t"
		"add	%0, %0, %1\n\t"
		"extui	%0, %0, 16, 16\n\t"
		"neg	%0, %0\n\t"
		"addi	%0, %0, -1\n\t"
		"extui	%0, %0, 0, 16\n\t"
		: "=r" (sum), "=&r" (__dummy)
		: "0" (sum));
	return (__force __sum16)sum;
}

/*
 *	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 sum, tmp, endaddr;

	__asm__ __volatile__(
		"sub		%0, %0, %0\n\t"
#if XCHAL_HAVE_LOOPS
		"loopgtz	%2, 2f\n\t"
#else
		"beqz		%2, 2f\n\t"
		"slli		%4, %2, 2\n\t"
		"add		%4, %4, %1\n\t"
		"0:\t"

Annotation

Implementation Notes