1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Network Checksum & Copy routine
  4 *
  5 * Copyright (C) 1999, 2003-2004 Hewlett-Packard Co
  6 *	Stephane Eranian <eranian@hpl.hp.com>
  7 *
  8 * Most of the code has been imported from Linux/Alpha
  9 */
 10
 11#include <linux/module.h>
 12#include <linux/types.h>
 13#include <linux/string.h>
 14
 15#include <linux/uaccess.h>
 16
 17/*
 18 * XXX Fixme: those 2 inlines are meant for debugging and will go away
 19 */
 20static inline unsigned
 21short from64to16(unsigned long x)
 22{
 23	/* add up 32-bit words for 33 bits */
 24	x = (x & 0xffffffff) + (x >> 32);
 25	/* add up 16-bit and 17-bit words for 17+c bits */
 26	x = (x & 0xffff) + (x >> 16);
 27	/* add up 16-bit and 2-bit for 16+c bit */
 28	x = (x & 0xffff) + (x >> 16);
 29	/* add up carry.. */
 30	x = (x & 0xffff) + (x >> 16);
 31	return x;
 32}
 33
 34static inline
 35unsigned long do_csum_c(const unsigned char * buff, int len, unsigned int psum)
 36{
 37	int odd, count;
 38	unsigned long result = (unsigned long)psum;
 39
 40	if (len <= 0)
 41		goto out;
 42	odd = 1 & (unsigned long) buff;
 43	if (odd) {
 44		result = *buff << 8;
 45		len--;
 46		buff++;
 47	}
 48	count = len >> 1;		/* nr of 16-bit words.. */
 49	if (count) {
 50		if (2 & (unsigned long) buff) {
 51			result += *(unsigned short *) buff;
 52			count--;
 53			len -= 2;
 54			buff += 2;
 55		}
 56		count >>= 1;		/* nr of 32-bit words.. */
 57		if (count) {
 58			if (4 & (unsigned long) buff) {
 59				result += *(unsigned int *) buff;
 60				count--;
 61				len -= 4;
 62				buff += 4;
 63			}
 64			count >>= 1;	/* nr of 64-bit words.. */
 65			if (count) {
 66				unsigned long carry = 0;
 67				do {
 68					unsigned long w = *(unsigned long *) buff;
 69					count--;
 70					buff += 8;
 71					result += carry;
 72					result += w;
 73					carry = (w > result);
 74				} while (count);
 75				result += carry;
 76				result = (result & 0xffffffff) + (result >> 32);
 77			}
 78			if (len & 4) {
 79				result += *(unsigned int *) buff;
 80				buff += 4;
 81			}
 82		}
 83		if (len & 2) {
 84			result += *(unsigned short *) buff;
 85			buff += 2;
 86		}
 87	}
 88	if (len & 1)
 89		result += *buff;
 90
 91	result = from64to16(result);
 92
 93	if (odd)
 94		result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
 95
 96out:
 97	return result;
 98}
 99
100/*
101 * XXX Fixme
102 *
103 * This is very ugly but temporary. THIS NEEDS SERIOUS ENHANCEMENTS.
104 * But it's very tricky to get right even in C.
105 */
106extern unsigned long do_csum(const unsigned char *, long);
107
108__wsum
109csum_partial_copy_from_user(const void __user *src, void *dst,
110				int len, __wsum psum, int *errp)
111{
112	unsigned long result;
113
114	/* XXX Fixme
115	 * for now we separate the copy from checksum for obvious
116	 * alignment difficulties. Look at the Alpha code and you'll be
117	 * scared.
118	 */
119
120	if (__copy_from_user(dst, src, len) != 0 && errp)
121		*errp = -EFAULT;
122
123	result = do_csum(dst, len);
124
125	/* add in old sum, and carry.. */
126	result += (__force u32)psum;
127	/* 32+c bits -> 32 bits */
128	result = (result & 0xffffffff) + (result >> 32);
129	return (__force __wsum)result;
130}
131
132EXPORT_SYMBOL(csum_partial_copy_from_user);
133
134__wsum
135csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum)
136{
137	return csum_partial_copy_from_user((__force const void __user *)src,
138					   dst, len, sum, NULL);
139}
140
141EXPORT_SYMBOL(csum_partial_copy_nocheck);