Subversion Repositories or1k

/*

 * 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) {

                        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 */

                                unsigned long zero = 0;

                        unsigned 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);

}

/*

 * this routine is used for miscellaneous IP-like checksums.

 */

unsigned short ip_compute_csum(unsigned char * buff, int len)

{

        return csum_fold(csum_partial(buff,len,0));

}