memzero.S 2.1 KB

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  1. /*
  2. * linux/arch/arm/lib/memzero.S
  3. *
  4. * Copyright (C) 1995-2000 Russell King
  5. *
  6. * This program is free software; you can redistribute it and/or modify
  7. * it under the terms of the GNU General Public License version 2 as
  8. * published by the Free Software Foundation.
  9. */
  10. #include <linux/linkage.h>
  11. #include <asm/assembler.h>
  12. .text
  13. .align 5
  14. .word 0
  15. /*
  16. * Align the pointer in r0. r3 contains the number of bytes that we are
  17. * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
  18. * don't bother; we use byte stores instead.
  19. */
  20. 1: subs r1, r1, #4 @ 1 do we have enough
  21. blt 5f @ 1 bytes to align with?
  22. cmp r3, #2 @ 1
  23. strltb r2, [r0], #1 @ 1
  24. strleb r2, [r0], #1 @ 1
  25. strb r2, [r0], #1 @ 1
  26. add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
  27. /*
  28. * The pointer is now aligned and the length is adjusted. Try doing the
  29. * memzero again.
  30. */
  31. ENTRY(__memzero)
  32. mov r2, #0 @ 1
  33. ands r3, r0, #3 @ 1 unaligned?
  34. bne 1b @ 1
  35. /*
  36. * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
  37. */
  38. cmp r1, #16 @ 1 we can skip this chunk if we
  39. blt 4f @ 1 have < 16 bytes
  40. /*
  41. * We need an extra register for this loop - save the return address and
  42. * use the LR
  43. */
  44. str lr, [sp, #-4]! @ 1
  45. mov ip, r2 @ 1
  46. mov lr, r2 @ 1
  47. 3: subs r1, r1, #64 @ 1 write 32 bytes out per loop
  48. stmgeia r0!, {r2, r3, ip, lr} @ 4
  49. stmgeia r0!, {r2, r3, ip, lr} @ 4
  50. stmgeia r0!, {r2, r3, ip, lr} @ 4
  51. stmgeia r0!, {r2, r3, ip, lr} @ 4
  52. bgt 3b @ 1
  53. ldmeqfd sp!, {pc} @ 1/2 quick exit
  54. /*
  55. * No need to correct the count; we're only testing bits from now on
  56. */
  57. tst r1, #32 @ 1
  58. stmneia r0!, {r2, r3, ip, lr} @ 4
  59. stmneia r0!, {r2, r3, ip, lr} @ 4
  60. tst r1, #16 @ 1 16 bytes or more?
  61. stmneia r0!, {r2, r3, ip, lr} @ 4
  62. ldr lr, [sp], #4 @ 1
  63. 4: tst r1, #8 @ 1 8 bytes or more?
  64. stmneia r0!, {r2, r3} @ 2
  65. tst r1, #4 @ 1 4 bytes or more?
  66. strne r2, [r0], #4 @ 1
  67. /*
  68. * When we get here, we've got less than 4 bytes to zero. We
  69. * may have an unaligned pointer as well.
  70. */
  71. 5: tst r1, #2 @ 1 2 bytes or more?
  72. strneb r2, [r0], #1 @ 1
  73. strneb r2, [r0], #1 @ 1
  74. tst r1, #1 @ 1 a byte left over
  75. strneb r2, [r0], #1 @ 1
  76. mov pc, lr @ 1