/arch/ppc64/kernel/vdso32/gettimeofday.S

https://bitbucket.org/evzijst/gittest · Assembly · 139 lines · 74 code · 15 blank · 50 comment · 0 complexity · 4f8e7b8ae9107229053c5864464576b6 MD5 · raw file

  1. /*
  2. * Userland implementation of gettimeofday() for 32 bits processes in a
  3. * ppc64 kernel for use in the vDSO
  4. *
  5. * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
  6. *
  7. * This program is free software; you can redistribute it and/or
  8. * modify it under the terms of the GNU General Public License
  9. * as published by the Free Software Foundation; either version
  10. * 2 of the License, or (at your option) any later version.
  11. */
  12. #include <linux/config.h>
  13. #include <asm/processor.h>
  14. #include <asm/ppc_asm.h>
  15. #include <asm/vdso.h>
  16. #include <asm/offsets.h>
  17. #include <asm/unistd.h>
  18. .text
  19. /*
  20. * Exact prototype of gettimeofday
  21. *
  22. * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
  23. *
  24. */
  25. V_FUNCTION_BEGIN(__kernel_gettimeofday)
  26. .cfi_startproc
  27. mflr r12
  28. .cfi_register lr,r12
  29. mr r10,r3 /* r10 saves tv */
  30. mr r11,r4 /* r11 saves tz */
  31. bl __get_datapage@local /* get data page */
  32. mr r9, r3 /* datapage ptr in r9 */
  33. bl __do_get_xsec@local /* get xsec from tb & kernel */
  34. bne- 2f /* out of line -> do syscall */
  35. /* seconds are xsec >> 20 */
  36. rlwinm r5,r4,12,20,31
  37. rlwimi r5,r3,12,0,19
  38. stw r5,TVAL32_TV_SEC(r10)
  39. /* get remaining xsec and convert to usec. we scale
  40. * up remaining xsec by 12 bits and get the top 32 bits
  41. * of the multiplication
  42. */
  43. rlwinm r5,r4,12,0,19
  44. lis r6,1000000@h
  45. ori r6,r6,1000000@l
  46. mulhwu r5,r5,r6
  47. stw r5,TVAL32_TV_USEC(r10)
  48. cmpli cr0,r11,0 /* check if tz is NULL */
  49. beq 1f
  50. lwz r4,CFG_TZ_MINUTEWEST(r9)/* fill tz */
  51. lwz r5,CFG_TZ_DSTTIME(r9)
  52. stw r4,TZONE_TZ_MINWEST(r11)
  53. stw r5,TZONE_TZ_DSTTIME(r11)
  54. 1: mtlr r12
  55. blr
  56. 2: mr r3,r10
  57. mr r4,r11
  58. li r0,__NR_gettimeofday
  59. sc
  60. b 1b
  61. .cfi_endproc
  62. V_FUNCTION_END(__kernel_gettimeofday)
  63. /*
  64. * This is the core of gettimeofday(), it returns the xsec
  65. * value in r3 & r4 and expects the datapage ptr (non clobbered)
  66. * in r9. clobbers r0,r4,r5,r6,r7,r8
  67. */
  68. __do_get_xsec:
  69. .cfi_startproc
  70. /* Check for update count & load values. We use the low
  71. * order 32 bits of the update count
  72. */
  73. 1: lwz r8,(CFG_TB_UPDATE_COUNT+4)(r9)
  74. andi. r0,r8,1 /* pending update ? loop */
  75. bne- 1b
  76. xor r0,r8,r8 /* create dependency */
  77. add r9,r9,r0
  78. /* Load orig stamp (offset to TB) */
  79. lwz r5,CFG_TB_ORIG_STAMP(r9)
  80. lwz r6,(CFG_TB_ORIG_STAMP+4)(r9)
  81. /* Get a stable TB value */
  82. 2: mftbu r3
  83. mftbl r4
  84. mftbu r0
  85. cmpl cr0,r3,r0
  86. bne- 2b
  87. /* Substract tb orig stamp. If the high part is non-zero, we jump to the
  88. * slow path which call the syscall. If it's ok, then we have our 32 bits
  89. * tb_ticks value in r7
  90. */
  91. subfc r7,r6,r4
  92. subfe. r0,r5,r3
  93. bne- 3f
  94. /* Load scale factor & do multiplication */
  95. lwz r5,CFG_TB_TO_XS(r9) /* load values */
  96. lwz r6,(CFG_TB_TO_XS+4)(r9)
  97. mulhwu r4,r7,r5
  98. mulhwu r6,r7,r6
  99. mullw r6,r7,r5
  100. addc r6,r6,r0
  101. /* At this point, we have the scaled xsec value in r4 + XER:CA
  102. * we load & add the stamp since epoch
  103. */
  104. lwz r5,CFG_STAMP_XSEC(r9)
  105. lwz r6,(CFG_STAMP_XSEC+4)(r9)
  106. adde r4,r4,r6
  107. addze r3,r5
  108. /* We now have our result in r3,r4. We create a fake dependency
  109. * on that result and re-check the counter
  110. */
  111. xor r0,r4,r4
  112. add r9,r9,r0
  113. lwz r0,(CFG_TB_UPDATE_COUNT+4)(r9)
  114. cmpl cr0,r8,r0 /* check if updated */
  115. bne- 1b
  116. /* Warning ! The caller expects CR:EQ to be set to indicate a
  117. * successful calculation (so it won't fallback to the syscall
  118. * method). We have overriden that CR bit in the counter check,
  119. * but fortunately, the loop exit condition _is_ CR:EQ set, so
  120. * we can exit safely here. If you change this code, be careful
  121. * of that side effect.
  122. */
  123. 3: blr
  124. .cfi_endproc