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kernel/linux-imx6_3.14.28/arch/arm/lib/csumpartial.S 3.05 KB
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  /*
   *  linux/arch/arm/lib/csumpartial.S
   *
   *  Copyright (C) 1995-1998 Russell King
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   */
  #include <linux/linkage.h>
  #include <asm/assembler.h>
  
  		.text
  
  /*
   * Function: __u32 csum_partial(const char *src, int len, __u32 sum)
   * Params  : r0 = buffer, r1 = len, r2 = checksum
   * Returns : r0 = new checksum
   */
  
  buf	.req	r0
  len	.req	r1
  sum	.req	r2
  td0	.req	r3
  td1	.req	r4	@ save before use
  td2	.req	r5	@ save before use
  td3	.req	lr
  
  .Lzero:		mov	r0, sum
  		add	sp, sp, #4
  		ldr	pc, [sp], #4
  
  		/*
  		 * Handle 0 to 7 bytes, with any alignment of source and
  		 * destination pointers.  Note that when we get here, C = 0
  		 */
  .Lless8:		teq	len, #0			@ check for zero count
  		beq	.Lzero
  
  		/* we must have at least one byte. */
  		tst	buf, #1			@ odd address?
  		movne	sum, sum, ror #8
  		ldrneb	td0, [buf], #1
  		subne	len, len, #1
  		adcnes	sum, sum, td0, put_byte_1
  
  .Lless4:		tst	len, #6
  		beq	.Lless8_byte
  
  		/* we are now half-word aligned */
  
  .Lless8_wordlp:
  #if __LINUX_ARM_ARCH__ >= 4
  		ldrh	td0, [buf], #2
  		sub	len, len, #2
  #else
  		ldrb	td0, [buf], #1
  		ldrb	td3, [buf], #1
  		sub	len, len, #2
  #ifndef __ARMEB__
  		orr	td0, td0, td3, lsl #8
  #else
  		orr	td0, td3, td0, lsl #8
  #endif
  #endif
  		adcs	sum, sum, td0
  		tst	len, #6
  		bne	.Lless8_wordlp
  
  .Lless8_byte:	tst	len, #1			@ odd number of bytes
  		ldrneb	td0, [buf], #1		@ include last byte
  		adcnes	sum, sum, td0, put_byte_0	@ update checksum
  
  .Ldone:		adc	r0, sum, #0		@ collect up the last carry
  		ldr	td0, [sp], #4
  		tst	td0, #1			@ check buffer alignment
  		movne	r0, r0, ror #8		@ rotate checksum by 8 bits
  		ldr	pc, [sp], #4		@ return
  
  .Lnot_aligned:	tst	buf, #1			@ odd address
  		ldrneb	td0, [buf], #1		@ make even
  		subne	len, len, #1
  		adcnes	sum, sum, td0, put_byte_1	@ update checksum
  
  		tst	buf, #2			@ 32-bit aligned?
  #if __LINUX_ARM_ARCH__ >= 4
  		ldrneh	td0, [buf], #2		@ make 32-bit aligned
  		subne	len, len, #2
  #else
  		ldrneb	td0, [buf], #1
  		ldrneb	ip, [buf], #1
  		subne	len, len, #2
  #ifndef __ARMEB__
  		orrne	td0, td0, ip, lsl #8
  #else
  		orrne	td0, ip, td0, lsl #8
  #endif
  #endif
  		adcnes	sum, sum, td0		@ update checksum
  		mov	pc, lr
  
  ENTRY(csum_partial)
  		stmfd	sp!, {buf, lr}
  		cmp	len, #8			@ Ensure that we have at least
  		blo	.Lless8			@ 8 bytes to copy.
  
  		tst	buf, #1
  		movne	sum, sum, ror #8
  
  		adds	sum, sum, #0		@ C = 0
  		tst	buf, #3			@ Test destination alignment
  		blne	.Lnot_aligned		@ align destination, return here
  
  1:		bics	ip, len, #31
  		beq	3f
  
  		stmfd	sp!, {r4 - r5}
  2:		ldmia	buf!, {td0, td1, td2, td3}
  		adcs	sum, sum, td0
  		adcs	sum, sum, td1
  		adcs	sum, sum, td2
  		adcs	sum, sum, td3
  		ldmia	buf!, {td0, td1, td2, td3}
  		adcs	sum, sum, td0
  		adcs	sum, sum, td1
  		adcs	sum, sum, td2
  		adcs	sum, sum, td3
  		sub	ip, ip, #32
  		teq	ip, #0
  		bne	2b
  		ldmfd	sp!, {r4 - r5}
  
  3:		tst	len, #0x1c		@ should not change C
  		beq	.Lless4
  
  4:		ldr	td0, [buf], #4
  		sub	len, len, #4
  		adcs	sum, sum, td0
  		tst	len, #0x1c
  		bne	4b
  		b	.Lless4
  ENDPROC(csum_partial)