checksum_32.h

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#ifndef _ASM_X86_CHECKSUM_32_H
#define _ASM_X86_CHECKSUM_32_H

#include <linux/in6.h>

#include <asm/uaccess.h>

/*
 * 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
 */
asmlinkage __wsum csum_partial(const void *buff, int len, __wsum sum);

/*
 * the same as csum_partial, but copies from src while it
 * checksums, and handles user-space pointer exceptions correctly, when needed.
 *
 * here even more important to align src and dst on a 32-bit (or even
 * better 64-bit) boundary
 */

asmlinkage __wsum csum_partial_copy_generic(const void *src, void *dst,
                        int len, __wsum sum,
                        int *src_err_ptr, int *dst_err_ptr);

/*
 *  Note: when you get a NULL pointer exception here this means someone
 *  passed in an incorrect kernel address to one of these functions.
 *
 *  If you use these functions directly please don't forget the
 *  access_ok().
 */
static inline __wsum csum_partial_copy_nocheck(const void *src, void *dst,
                           int len, __wsum sum)
{
    return csum_partial_copy_generic(src, dst, len, sum, NULL, NULL);
}

static inline __wsum csum_partial_copy_from_user(const void __user *src,
                         void *dst,
                         int len, __wsum sum,
                         int *err_ptr)
{
    might_sleep();
    return csum_partial_copy_generic((__force void *)src, dst,
                     len, sum, err_ptr, NULL);
}

/*
 *  This is a version of ip_compute_csum() optimized for IP headers,
 *  which always checksum on 4 octet boundaries.
 *
 *  By Jorge Cwik <[email protected]>, adapted for linux by
 *  Arnt Gulbrandsen.
 */
static inline __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
{
    unsigned int sum;

    asm volatile("movl (%1), %0 ;\n"
             "subl $4, %2   ;\n"
             "jbe 2f        ;\n"
             "addl 4(%1), %0    ;\n"
             "adcl 8(%1), %0    ;\n"
             "adcl 12(%1), %0;\n"
             "1:    adcl 16(%1), %0 ;\n"
             "lea 4(%1), %1 ;\n"
             "decl %2   ;\n"
             "jne 1b        ;\n"
             "adcl $0, %0   ;\n"
             "movl %0, %2   ;\n"
             "shrl $16, %0  ;\n"
             "addw %w2, %w0 ;\n"
             "adcl $0, %0   ;\n"
             "notl %0   ;\n"
             "2:        ;\n"
    /* Since the input registers which are loaded with iph and ihl
       are modified, we must also specify them as outputs, or gcc
       will assume they contain their original values. */
             : "=r" (sum), "=r" (iph), "=r" (ihl)
             : "1" (iph), "2" (ihl)
             : "memory");
    return (__force __sum16)sum;
}

/*
 *  Fold a partial checksum
 */

static inline __sum16 csum_fold(__wsum sum)
{
    asm("addl %1, %0        ;\n"
        "adcl $0xffff, %0   ;\n"
        : "=r" (sum)
        : "r" ((__force u32)sum << 16),
          "0" ((__force u32)sum & 0xffff0000));
    return (__force __sum16)(~(__force u32)sum >> 16);
}

static inline __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
                    unsigned short len,
                    unsigned short proto,
                    __wsum sum)
{
    asm("addl %1, %0    ;\n"
        "adcl %2, %0    ;\n"
        "adcl %3, %0    ;\n"
        "adcl $0, %0    ;\n"
        : "=r" (sum)
        : "g" (daddr), "g"(saddr),
          "g" ((len + proto) << 8), "0" (sum));
    return sum;
}

/*
 * computes the checksum of the TCP/UDP pseudo-header
 * returns a 16-bit checksum, already complemented
 */
static inline __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
                    unsigned short len,
                    unsigned short proto,
                    __wsum sum)
{
    return csum_fold(csum_tcpudp_nofold(saddr, daddr, len, proto, sum));
}

/*
 * this routine is used for miscellaneous IP-like checksums, mainly
 * in icmp.c
 */

static inline __sum16 ip_compute_csum(const void *buff, int len)
{
    return csum_fold(csum_partial(buff, len, 0));
}

#define _HAVE_ARCH_IPV6_CSUM
static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr,
                      const struct in6_addr *daddr,
                      __u32 len, unsigned short proto,
                      __wsum sum)
{
    asm("addl 0(%1), %0 ;\n"
        "adcl 4(%1), %0 ;\n"
        "adcl 8(%1), %0 ;\n"
        "adcl 12(%1), %0    ;\n"
        "adcl 0(%2), %0 ;\n"
        "adcl 4(%2), %0 ;\n"
        "adcl 8(%2), %0 ;\n"
        "adcl 12(%2), %0    ;\n"
        "adcl %3, %0    ;\n"
        "adcl %4, %0    ;\n"
        "adcl $0, %0    ;\n"
        : "=&r" (sum)
        : "r" (saddr), "r" (daddr),
          "r" (htonl(len)), "r" (htonl(proto)), "0" (sum)
        : "memory");

    return csum_fold(sum);
}

/*
 *  Copy and checksum to user
 */
#define HAVE_CSUM_COPY_USER
static inline __wsum csum_and_copy_to_user(const void *src,
                       void __user *dst,
                       int len, __wsum sum,
                       int *err_ptr)
{
    might_sleep();
    if (access_ok(VERIFY_WRITE, dst, len))
        return csum_partial_copy_generic(src, (__force void *)dst,
                         len, sum, NULL, err_ptr);

    if (len)
        *err_ptr = -EFAULT;

    return (__force __wsum)-1; /* invalid checksum */
}

#endif /* _ASM_X86_CHECKSUM_32_H */