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kernel/linux-imx6_3.14.28/arch/arm/lib/memzero.S 2.77 KB
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  /*
   *  linux/arch/arm/lib/memzero.S
   *
   *  Copyright (C) 1995-2000 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
  	.align	5
  	.word	0
  /*
   * Align the pointer in r0.  r3 contains the number of bytes that we are
   * mis-aligned by, and r1 is the number of bytes.  If r1 < 4, then we
   * don't bother; we use byte stores instead.
   */
  1:	subs	r1, r1, #4		@ 1 do we have enough
  	blt	5f			@ 1 bytes to align with?
  	cmp	r3, #2			@ 1
  	strltb	r2, [r0], #1		@ 1
  	strleb	r2, [r0], #1		@ 1
  	strb	r2, [r0], #1		@ 1
  	add	r1, r1, r3		@ 1 (r1 = r1 - (4 - r3))
  /*
   * The pointer is now aligned and the length is adjusted.  Try doing the
   * memzero again.
   */
  
  ENTRY(__memzero)
  	mov	r2, #0			@ 1
  	ands	r3, r0, #3		@ 1 unaligned?
  	bne	1b			@ 1
  /*
   * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
   */
  	cmp	r1, #16			@ 1 we can skip this chunk if we
  	blt	4f			@ 1 have < 16 bytes
  
  #if ! CALGN(1)+0
  
  /*
   * We need an extra register for this loop - save the return address and
   * use the LR
   */
  	str	lr, [sp, #-4]!		@ 1
  	mov	ip, r2			@ 1
  	mov	lr, r2			@ 1
  
  3:	subs	r1, r1, #64		@ 1 write 32 bytes out per loop
  	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
  	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
  	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
  	stmgeia	r0!, {r2, r3, ip, lr}	@ 4
  	bgt	3b			@ 1
  	ldmeqfd	sp!, {pc}		@ 1/2 quick exit
  /*
   * No need to correct the count; we're only testing bits from now on
   */
  	tst	r1, #32			@ 1
  	stmneia	r0!, {r2, r3, ip, lr}	@ 4
  	stmneia	r0!, {r2, r3, ip, lr}	@ 4
  	tst	r1, #16			@ 1 16 bytes or more?
  	stmneia	r0!, {r2, r3, ip, lr}	@ 4
  	ldr	lr, [sp], #4		@ 1
  
  #else
  
  /*
   * This version aligns the destination pointer in order to write
   * whole cache lines at once.
   */
  
  	stmfd	sp!, {r4-r7, lr}
  	mov	r4, r2
  	mov	r5, r2
  	mov	r6, r2
  	mov	r7, r2
  	mov	ip, r2
  	mov	lr, r2
  
  	cmp	r1, #96
  	andgts	ip, r0, #31
  	ble	3f
  
  	rsb	ip, ip, #32
  	sub	r1, r1, ip
  	movs	ip, ip, lsl #(32 - 4)
  	stmcsia	r0!, {r4, r5, r6, r7}
  	stmmiia	r0!, {r4, r5}
  	movs	ip, ip, lsl #2
  	strcs	r2, [r0], #4
  
  3:	subs	r1, r1, #64
  	stmgeia	r0!, {r2-r7, ip, lr}
  	stmgeia	r0!, {r2-r7, ip, lr}
  	bgt	3b
  	ldmeqfd	sp!, {r4-r7, pc}
  
  	tst	r1, #32
  	stmneia	r0!, {r2-r7, ip, lr}
  	tst	r1, #16
  	stmneia	r0!, {r4-r7}
  	ldmfd	sp!, {r4-r7, lr}
  
  #endif
  
  4:	tst	r1, #8			@ 1 8 bytes or more?
  	stmneia	r0!, {r2, r3}		@ 2
  	tst	r1, #4			@ 1 4 bytes or more?
  	strne	r2, [r0], #4		@ 1
  /*
   * When we get here, we've got less than 4 bytes to zero.  We
   * may have an unaligned pointer as well.
   */
  5:	tst	r1, #2			@ 1 2 bytes or more?
  	strneb	r2, [r0], #1		@ 1
  	strneb	r2, [r0], #1		@ 1
  	tst	r1, #1			@ 1 a byte left over
  	strneb	r2, [r0], #1		@ 1
  	mov	pc, lr			@ 1
  ENDPROC(__memzero)