/*
* 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>
* Pentium Pro/II routines:
* Alexander Kjeldaas <astor@guardian.no>
* Finn Arne Gangstad <finnag@guardian.no>
* 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.
* Andi Kleen, add zeroing on error
* converted to pure assembler
*
* 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 <asm/errno.h>
#include <asm/asm.h>
#include <asm/export.h>
/*
* computes a partial checksum, e.g. for TCP/UDP fragments
*/
/*
unsigned int csum_partial(const unsigned char * buff, int len, unsigned int sum)
*/
.text
.align 4
.globl csum_partial
#ifndef CONFIG_X86_USE_PPRO_CHECKSUM
/*
* 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 twofold 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.
*/
csum_partial:
pushl %esi
pushl %ebx
movl 20(%esp),%eax # Function arg: unsigned int sum
movl 16(%esp),%ecx # Function arg: int len
movl 12(%esp),%esi # Function arg: unsigned char *buff
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:
popl %ebx
popl %esi
ret
#else
/* Version for PentiumII/PPro */
csum_partial:
pushl %esi
pushl %ebx
movl 20(%esp),%eax # Function arg: unsigned int sum
movl 16(%esp),%ecx # Function arg: int len
movl 12(%esp),%esi # Function arg: const unsigned char *buf
testl $2, %esi
jnz 30f
10:
movl %ecx, %edx
movl %ecx, %ebx
andl $0x7c, %ebx
shrl $7, %ecx
addl %ebx,%esi
shrl $2, %ebx
negl %ebx
lea 45f(%ebx,%ebx,2), %ebx
testl %esi, %esi
jmp *%ebx
# Handle 2-byte-aligned regions
20: addw (%esi), %ax
lea 2(%esi), %esi
adcl $0, %eax
jmp 10b
30: subl $2, %ecx
ja 20b
je 32f
movzbl (%esi),%ebx # csumming 1 byte, 2-aligned
addl %ebx, %eax
adcl $0, %eax
jmp 80f
32:
addw (%esi), %ax # csumming 2 bytes, 2-aligned
adcl $0, %eax
jmp 80f
40:
addl -128(%esi), %eax
adcl -124(%esi), %eax
adcl -120(%esi), %eax
adcl -116(%esi), %eax
adcl -112(%esi), %eax
adcl -108(%esi), %eax
adcl -104(%esi), %eax
adcl -100(%esi), %eax
adcl -96(%esi), %eax
adcl -92(%esi), %eax
adcl -88(%esi), %eax
adcl -84(%esi), %eax
adcl -80(%esi), %eax
adcl -76(%esi), %eax
adcl -72(%esi), %eax
adcl -68(%esi), %eax
adcl -64(%esi), %eax
adcl -60(%esi), %eax
adcl -56(%esi), %eax
adcl -52(%esi), %eax
adcl -48(%esi), %eax
adcl -44(%esi), %eax
adcl -40(%esi), %eax
adcl -36(%esi), %eax
adcl -32(%esi), %eax
adcl -28(%esi), %eax
adcl -24(%esi), %eax
adcl -20(%esi), %eax
adcl -16(%esi), %eax
adcl -12(%esi), %eax
adcl -8(%esi), %eax
adcl -4(%esi), %eax
45:
lea 128(%esi), %esi
adcl $0, %eax
dec %ecx
jge 40b
movl %edx, %ecx
50: andl $3, %ecx
jz 80f
# Handle the last 1-3 bytes without jumping
notl %ecx # 1->2, 2->1, 3->0, higher bits are masked
movl $0xffffff,%ebx # by the shll and shrl instructions
shll $3,%ecx
shrl %cl,%ebx
andl -128(%esi),%ebx # esi is 4-aligned so should be ok
addl %ebx,%eax
adcl $0,%eax
80:
popl %ebx
popl %esi
ret
#endif
EXPORT_SYMBOL(csum_partial)
