1 files changed, 150 insertions, 0 deletions

diff --git a/arch/x86_64/lib/csum-partial.c b/arch/x86_64/lib/csum-partial.c
new file mode 100644
index 000000000000..5384e227cdf6
--- /dev/null
+++ b/arch/x86_64/lib/csum-partial.c
@@ -0,0 +1,150 @@
+/*
+ * arch/x86_64/lib/csum-partial.c
+ *
+ * This file contains network checksum routines that are better done
+ * in an architecture-specific manner due to speed.
+ */
+ 
+#include <linux/compiler.h>
+#include <linux/module.h>
+#include <asm/checksum.h>
+
+#define __force_inline inline __attribute__((always_inline))
+
+static inline unsigned short from32to16(unsigned a) 
+{
+        unsigned short b = a >> 16; 
+        asm("addw %w2,%w0\n\t"
+            "adcw $0,%w0\n" 
+            : "=r" (b)
+            : "0" (b), "r" (a));
+        return b;
+}
+
+/*
+ * Do a 64-bit checksum on an arbitrary memory area.
+ * Returns a 32bit checksum.
+ *
+ * This isn't as time critical as it used to be because many NICs
+ * do hardware checksumming these days.
+ * 
+ * Things tried and found to not make it faster:
+ * Manual Prefetching
+ * Unrolling to an 128 bytes inner loop.
+ * Using interleaving with more registers to break the carry chains.
+ */
+static __force_inline unsigned do_csum(const unsigned char *buff, unsigned len)
+{
+        unsigned odd, count;
+        unsigned long result = 0;
+
+        if (unlikely(len == 0))
+                return result; 
+        odd = 1 & (unsigned long) buff;
+        if (unlikely(odd)) {
+                result = *buff << 8;
+                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 zero;
+                        unsigned count64;
+                        if (4 & (unsigned long) buff) {
+                                result += *(unsigned int *) buff;
+                                count--;
+                                len -= 4;
+                                buff += 4;
+                        }
+                        count >>= 1;    /* nr of 64-bit words.. */
+
+                        /* main loop using 64byte blocks */
+                        zero = 0;
+                        count64 = count >> 3;
+                        while (count64) { 
+                                asm("addq 0*8(%[src]),%[res]\n\t"
+                                    "adcq 1*8(%[src]),%[res]\n\t"
+                                    "adcq 2*8(%[src]),%[res]\n\t"
+                                    "adcq 3*8(%[src]),%[res]\n\t"
+                                    "adcq 4*8(%[src]),%[res]\n\t"
+                                    "adcq 5*8(%[src]),%[res]\n\t"
+                                    "adcq 6*8(%[src]),%[res]\n\t"
+                                    "adcq 7*8(%[src]),%[res]\n\t"
+                                    "adcq %[zero],%[res]"
+                                    : [res] "=r" (result)
+                                    : [src] "r" (buff), [zero] "r" (zero),
+                                    "[res]" (result));
+                                buff += 64;
+                                count64--;
+                        }
+
+                        /* last upto 7 8byte blocks */
+                        count %= 8; 
+                        while (count) { 
+                                asm("addq %1,%0\n\t"
+                                    "adcq %2,%0\n" 
+                                            : "=r" (result)
+                                    : "m" (*(unsigned long *)buff), 
+                                    "r" (zero),  "0" (result));
+                                --count; 
+                                        buff += 8;
+                        }
+                        result = add32_with_carry(result>>32,
+                                                  result&0xffffffff); 
+
+                        if (len & 4) {
+                                result += *(unsigned int *) buff;
+                                buff += 4;
+                        }
+                }
+                if (len & 2) {
+                        result += *(unsigned short *) buff;
+                        buff += 2;
+                }
+        }
+        if (len & 1)
+                result += *buff;
+        result = add32_with_carry(result>>32, result & 0xffffffff); 
+        if (unlikely(odd)) { 
+                result = from32to16(result);
+                result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
+        }
+        return result;
+}
+
+/*
+ * 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 64-bit boundary
+ */
+unsigned csum_partial(const unsigned char *buff, unsigned len, unsigned sum)
+{
+        return add32_with_carry(do_csum(buff, len), sum); 
+}
+
+EXPORT_SYMBOL(csum_partial);
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+unsigned short ip_compute_csum(unsigned char * buff, int len)
+{
+        return csum_fold(csum_partial(buff,len,0));
+}
+