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/*
* 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>
* Lots of code moved from tcp.c and ip.c; see those files
* for more names.
*
* Changes: Ingo Molnar, converted csum_partial_copy() to 2.1 exception
* handling.
*
* 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.
*/
#include <net/checksum.h>
/*
* computes a partial checksum, e.g. for TCP/UDP fragments
*/
unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum) {
/*
* Experiments with ethernet and slip connections show that buff
* is aligned on either a 2-byte or 4-byte boundary. We get at
* least a 2x speedup on 486 and Pentium if it is 4-byte aligned.
* Fortunately, it is easy to convert 2-byte alignment to 4-byte
* alignment for the unrolled loop.
*/
__asm__("
testl $2, %%esi # Check alignment.
jz 2f # Jump if alignment is ok.
subl $2, %%ecx # Alignment uses up two bytes.
jae 1f # Jump if we had at least two bytes.
addl $2, %%ecx # ecx was < 2. Deal with it.
jmp 4f
1: movw (%%esi), %%bx
addl $2, %%esi
addw %%bx, %%ax
adcl $0, %%eax
2:
movl %%ecx, %%edx
shrl $5, %%ecx
jz 2f
testl %%esi, %%esi
1: movl (%%esi), %%ebx
adcl %%ebx, %%eax
movl 4(%%esi), %%ebx
adcl %%ebx, %%eax
movl 8(%%esi), %%ebx
adcl %%ebx, %%eax
movl 12(%%esi), %%ebx
adcl %%ebx, %%eax
movl 16(%%esi), %%ebx
adcl %%ebx, %%eax
movl 20(%%esi), %%ebx
adcl %%ebx, %%eax
movl 24(%%esi), %%ebx
adcl %%ebx, %%eax
movl 28(%%esi), %%ebx
adcl %%ebx, %%eax
lea 32(%%esi), %%esi
dec %%ecx
jne 1b
adcl $0, %%eax
2: movl %%edx, %%ecx
andl $0x1c, %%edx
je 4f
shrl $2, %%edx # This clears CF
3: adcl (%%esi), %%eax
lea 4(%%esi), %%esi
dec %%edx
jne 3b
adcl $0, %%eax
4: andl $3, %%ecx
jz 7f
cmpl $2, %%ecx
jb 5f
movw (%%esi),%%cx
leal 2(%%esi),%%esi
je 6f
shll $16,%%ecx
5: movb (%%esi),%%cl
6: addl %%ecx,%%eax
adcl $0, %%eax
7: "
: "=a"(sum)
: "0"(sum), "c"(len), "S"(buff)
: "bx", "cx", "dx", "si");
return(sum);
}
/*
* Copy from ds while checksumming, otherwise like csum_partial
*
* The macros SRC and DST specify the type of access for the instruction.
* thus we can call a custom exception handler for all access types.
*
* FIXME: could someone double check wether i havent mixed up some SRC and
* DST definitions? It's damn hard to trigger all cases, i hope i got
* them all but theres no guarantee ...
*/
#define SRC(y...) \
" 9999: "#y"; \n \
.section __ex_table, \"a\"; \n \
.long 9999b, src_access_fault \n \
.previous"
#define DST(y...) \
" 9999: "#y"; \n \
.section __ex_table, \"a\"; \n \
.long 9999b, dst_access_fault \n \
.previous"
unsigned int csum_partial_copy_generic (const char *src, char *dst,
int len, int sum, int *src_err_ptr, int *dst_err_ptr)
{
__asm__ __volatile__ ( "
testl $2, %%edi # Check alignment.
jz 2f # Jump if alignment is ok.
subl $2, %%ecx # Alignment uses up two bytes.
jae 1f # Jump if we had at least two bytes.
addl $2, %%ecx # ecx was < 2. Deal with it.
jmp 4f
"SRC( 1: movw (%%esi), %%bx )"
addl $2, %%esi
"DST( movw %%bx, (%%edi) )"
addl $2, %%edi
addw %%bx, %%ax
adcl $0, %%eax
2:
pushl %%ecx
shrl $5, %%ecx
jz 2f
testl %%esi, %%esi
"SRC( 1: movl (%%esi), %%ebx )"
"SRC( movl 4(%%esi), %%edx )"
adcl %%ebx, %%eax
"DST( movl %%ebx, (%%edi) )"
adcl %%edx, %%eax
"DST( movl %%edx, 4(%%edi) )"
"SRC( movl 8(%%esi), %%ebx )"
"SRC( movl 12(%%esi), %%edx )"
adcl %%ebx, %%eax
"DST( movl %%ebx, 8(%%edi) )"
adcl %%edx, %%eax
"DST( movl %%edx, 12(%%edi) )"
"SRC( movl 16(%%esi), %%ebx )"
"SRC( movl 20(%%esi), %%edx )"
adcl %%ebx, %%eax
"DST( movl %%ebx, 16(%%edi) )"
adcl %%edx, %%eax
"DST( movl %%edx, 20(%%edi) )"
"SRC( movl 24(%%esi), %%ebx )"
"SRC( movl 28(%%esi), %%edx )"
adcl %%ebx, %%eax
"DST( movl %%ebx, 24(%%edi) )"
adcl %%edx, %%eax
"DST( movl %%edx, 28(%%edi) )"
"SRC( lea 32(%%esi), %%esi )"
"DST( lea 32(%%edi), %%edi )"
dec %%ecx
jne 1b
adcl $0, %%eax
2: popl %%edx
movl %%edx, %%ecx
andl $0x1c, %%edx
je 4f
shrl $2, %%edx # This clears CF
"SRC( 3: movl (%%esi), %%ebx )"
adcl %%ebx, %%eax
"DST( movl %%ebx, (%%edi) )"
"SRC( lea 4(%%esi), %%esi )"
"DST( lea 4(%%edi), %%edi )"
dec %%edx
jne 3b
adcl $0, %%eax
4: andl $3, %%ecx
jz 7f
cmpl $2, %%ecx
jb 5f
"SRC( movw (%%esi), %%cx )"
"SRC( leal 2(%%esi), %%esi )"
"DST( movw %%cx, (%%edi) )"
"DST( leal 2(%%edi), %%edi )"
je 6f
shll $16,%%ecx
"SRC( 5: movb (%%esi), %%cl )"
"DST( movb %%cl, (%%edi) )"
6: addl %%ecx, %%eax
adcl $0, %%eax
7:
end_of_body:
# Exception handler:
################################################
#
.section .fixup, \"a\" #
#
common_fixup: #
#
movl %7, (%%ebx) #
#
# FIXME: do zeroing of rest of the buffer here. #
#
jmp end_of_body #
#
src_access_fault: #
movl %1, %%ebx #
jmp common_fixup #
#
dst_access_fault: #
movl %2, %%ebx #
jmp common_fixup #
#
.previous #
#
################################################
"
: "=a" (sum), "=m" (src_err_ptr), "=m" (dst_err_ptr)
: "0" (sum), "c" (len), "S" (src), "D" (dst),
"i" (-EFAULT)
: "bx", "cx", "dx", "si", "di" );
return(sum);
}
#undef SRC
#undef DST
/*
* FIXME: old compatibility stuff, will be removed soon.
*/
unsigned int csum_partial_copy( const char *src, char *dst, int len, int sum)
{
int src_err=0, dst_err=0;
sum = csum_partial_copy_generic ( src, dst, len, sum, &src_err, &dst_err);
if (src_err || dst_err)
printk("old csum_partial_copy_fromuser(), tell mingo to convert me.\n");
return sum;
}
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