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Diffstat (limited to 'arch/x86/lib/csum-partial_64.c')
-rw-r--r--arch/x86/lib/csum-partial_64.c150
1 files changed, 150 insertions, 0 deletions
diff --git a/arch/x86/lib/csum-partial_64.c b/arch/x86/lib/csum-partial_64.c
new file mode 100644
index 000000000000..bc503f506903
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+++ b/arch/x86/lib/csum-partial_64.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>
+
+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 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
+ */
+__wsum csum_partial(const void *buff, int len, __wsum sum)
+{
+ return (__force __wsum)add32_with_carry(do_csum(buff, len),
+ (__force u32)sum);
+}
+
+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 csum_fold(csum_partial(buff,len,0));
+}
+EXPORT_SYMBOL(ip_compute_csum);
+