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Source code of Windows XP (NT5)
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windows-xp/Source/XPSP1/NT/base/ntos/ke/amd64/zero.asm

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  1. title "Zero Page"
  2. ;++
  3. ;
  4. ; Copyright (c) 2001 Microsoft Corporation
  5. ;
  6. ; Module Name:
  7. ;
  8. ; zero.asm
  9. ;
  10. ; Abstract:
  11. ;
  12. ; This module implements the architecture dependent code necessary to
  13. ; zero a page of memory is the fastest possible way.
  14. ;
  15. ; Author:
  16. ;
  17. ; David N. Cutler (davec) 9-Jan-2001
  18. ;
  19. ; Environment:
  20. ;
  21. ; Kernel mode only.
  22. ;
  23. ;--
  25. include ksamd64.inc
  27. subttl "Zero Page"
  28. ;++
  29. ;
  30. ; VOID
  31. ; KeZeroPage (
  32. ; IN PVOID PageBase
  33. ; )
  34. ;
  35. ; Routine Description:
  36. ;
  37. ; This routine zeros the specfied page of memory using nontemporal moves.
  38. ;
  39. ; Arguments:
  40. ;
  41. ; PageBase (rcx) - Supplies the address of the page to zero.
  42. ;
  43. ; Return Value:
  44. ;
  45. ; None.
  46. ;
  47. ;--
  49. LEAF_ENTRY KeZeroPage, _TEXT$00
  51. pxor xmm0, xmm0 ; clear register
  52. mov eax, PAGE_SIZE / 128 ; compute loop count
  53. KeZP10: movntdq 0[rcx], xmm0 ; zero 128-byte block
  54. movntdq 16[rcx], xmm0 ;
  55. movntdq 32[rcx], xmm0 ;
  56. movntdq 48[rcx], xmm0 ;
  57. movntdq 64[rcx], xmm0 ;
  58. movntdq 80[rcx], xmm0 ;
  59. movntdq 96[rcx], xmm0 ;
  60. movntdq 112[rcx], xmm0 ;
  61. add rcx, 128 ; advance to next block
  62. dec eax ; decrement loop count
  63. jnz short KeZP10 ; if nz, more bytes to zero
  64. sfence ; force stores to complete
  65. ret ;
  68. LEAF_END KeZeroPage, _TEXT$00
  70. end