add generic lib/checksum.c

Add a generic (unoptimized) implementation of checksum.c in pure C
for use by all architectures that cannot be bother with implementing
their own version.

Based on microblaze code by Michal Simek <monstr@monstr.eu>

Cc: Michal Simek <monstr@monstr.eu>
Signed-off-by: Remis Lima Baima <remis.developer@googlemail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 193 insertions, 0 deletions

diff --git a/lib/checksum.c b/lib/checksum.c
new file mode 100644
index 000000000000..12e5a1c91cda
--- /dev/null
+++ b/lib/checksum.c
@@ -0,0 +1,193 @@
+/*
+ *
+ * INET         An implementation of the TCP/IP protocol suite for the LINUX
+ *              operating system.  INET is implemented using the  BSD Socket
+ *              interface as the means of communication with the user level.
+ *
+ *              IP/TCP/UDP checksumming routines
+ *
+ * Authors:     Jorge Cwik, <jorge@laser.satlink.net>
+ *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *              Tom May, <ftom@netcom.com>
+ *              Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
+ *              Lots of code moved from tcp.c and ip.c; see those files
+ *              for more names.
+ *
+ * 03/02/96     Jes Sorensen, Andreas Schwab, Roman Hodek:
+ *              Fixed some nasty bugs, causing some horrible crashes.
+ *              A: At some points, the sum (%0) was used as
+ *              length-counter instead of the length counter
+ *              (%1). Thanks to Roman Hodek for pointing this out.
+ *              B: GCC seems to mess up if one uses too many
+ *              data-registers to hold input values and one tries to
+ *              specify d0 and d1 as scratch registers. Letting gcc
+ *              choose these registers itself solves the problem.
+ *
+ *              This program is free software; you can redistribute it and/or
+ *              modify it under the terms of the GNU General Public License
+ *              as published by the Free Software Foundation; either version
+ *              2 of the License, or (at your option) any later version.
+ */
+
+/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
+ kills, so most of the assembly has to go. */
+
+#include <linux/module.h>
+#include <net/checksum.h>
+
+#include <asm/byteorder.h>
+
+static inline unsigned short from32to16(unsigned long x)
+{
+        /* add up 16-bit and 16-bit for 16+c bit */
+        x = (x & 0xffff) + (x >> 16);
+        /* add up carry.. */
+        x = (x & 0xffff) + (x >> 16);
+        return x;
+}
+
+static unsigned int do_csum(const unsigned char *buff, int len)
+{
+        int odd, count;
+        unsigned long result = 0;
+
+        if (len <= 0)
+                goto out;
+        odd = 1 & (unsigned long) buff;
+        if (odd) {
+                result = *buff;
+                len--;
+                buff++;
+        }
+        count = len >> 1;               /* nr of 16-bit words.. */
+        if (count) {
+                if (2 & (unsigned long) buff) {
+                        result += *(unsigned short *) buff;
+                        count--;
+                        len -= 2;
+                        buff += 2;
+                }
+                count >>= 1;            /* nr of 32-bit words.. */
+                if (count) {
+                        unsigned long carry = 0;
+                        do {
+                                unsigned long w = *(unsigned long *) buff;
+                                count--;
+                                buff += 4;
+                                result += carry;
+                                result += w;
+                                carry = (w > result);
+                        } while (count);
+                        result += carry;
+                        result = (result & 0xffff) + (result >> 16);
+                }
+                if (len & 2) {
+                        result += *(unsigned short *) buff;
+                        buff += 2;
+                }
+        }
+        if (len & 1)
+                result += (*buff << 8);
+        result = from32to16(result);
+        if (odd)
+                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+out:
+        return result;
+}
+
+/*
+ *      This is a version of ip_compute_csum() optimized for IP headers,
+ *      which always checksum on 4 octet boundaries.
+ */
+__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
+{
+        return (__force __sum16)~do_csum(iph, ihl*4);
+}
+EXPORT_SYMBOL(ip_fast_csum);
+
+/*
+ * 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 wsum)
+{
+        unsigned int sum = (__force unsigned int)wsum;
+        unsigned int result = do_csum(buff, len);
+
+        /* add in old sum, and carry.. */
+        result += sum;
+        if (sum > result)
+                result += 1;
+        return (__force __wsum)result;
+}
+EXPORT_SYMBOL(csum_partial);
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+__sum16 ip_compute_csum(const void *buff, int len)
+{
+        return (__force __sum16)~do_csum(buff, len);
+}
+EXPORT_SYMBOL(ip_compute_csum);
+
+/*
+ * copy from fs while checksumming, otherwise like csum_partial
+ */
+__wsum
+csum_partial_copy_from_user(const void __user *src, void *dst, int len,
+                                                __wsum sum, int *csum_err)
+{
+        int missing;
+
+        missing = __copy_from_user(dst, src, len);
+        if (missing) {
+                memset(dst + len - missing, 0, missing);
+                *csum_err = -EFAULT;
+        } else
+                *csum_err = 0;
+
+        return csum_partial(dst, len, sum);
+}
+EXPORT_SYMBOL(csum_partial_copy_from_user);
+
+/*
+ * copy from ds while checksumming, otherwise like csum_partial
+ */
+__wsum
+csum_partial_copy(const void *src, void *dst, int len, __wsum sum)
+{
+        memcpy(dst, src, len);
+        return csum_partial(dst, len, sum);
+}
+EXPORT_SYMBOL(csum_partial_copy);
+
+#ifndef csum_tcpudp_nofold
+__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
+                        unsigned short len,
+                        unsigned short proto,
+                        __wsum sum)
+{
+        unsigned long long s = (__force u32)sum;
+
+        s += (__force u32)saddr;
+        s += (__force u32)daddr;
+#ifdef __BIG_ENDIAN
+        s += proto + len;
+#else
+        s += (proto + len) << 8;
+#endif
+        s += (s >> 32);
+        return (__force __wsum)s;
+}
+EXPORT_SYMBOL(csum_tcpudp_nofold);
+#endif