printk-formats.txt 5.6 KB

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  1. If variable is of Type, use printk format specifier:
  2. ---------------------------------------------------------
  3. int %d or %x
  4. unsigned int %u or %x
  5. long %ld or %lx
  6. unsigned long %lu or %lx
  7. long long %lld or %llx
  8. unsigned long long %llu or %llx
  9. size_t %zu or %zx
  10. ssize_t %zd or %zx
  11. Raw pointer value SHOULD be printed with %p. The kernel supports
  12. the following extended format specifiers for pointer types:
  13. Symbols/Function Pointers:
  14. %pF versatile_init+0x0/0x110
  15. %pf versatile_init
  16. %pS versatile_init+0x0/0x110
  17. %ps versatile_init
  18. %pB prev_fn_of_versatile_init+0x88/0x88
  19. For printing symbols and function pointers. The 'S' and 's' specifiers
  20. result in the symbol name with ('S') or without ('s') offsets. Where
  21. this is used on a kernel without KALLSYMS - the symbol address is
  22. printed instead.
  23. The 'B' specifier results in the symbol name with offsets and should be
  24. used when printing stack backtraces. The specifier takes into
  25. consideration the effect of compiler optimisations which may occur
  26. when tail-call's are used and marked with the noreturn GCC attribute.
  27. On ia64, ppc64 and parisc64 architectures function pointers are
  28. actually function descriptors which must first be resolved. The 'F' and
  29. 'f' specifiers perform this resolution and then provide the same
  30. functionality as the 'S' and 's' specifiers.
  31. Kernel Pointers:
  32. %pK 0x01234567 or 0x0123456789abcdef
  33. For printing kernel pointers which should be hidden from unprivileged
  34. users. The behaviour of %pK depends on the kptr_restrict sysctl - see
  35. Documentation/sysctl/kernel.txt for more details.
  36. Struct Resources:
  37. %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
  38. [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
  39. %pR [mem 0x60000000-0x6fffffff pref] or
  40. [mem 0x0000000060000000-0x000000006fffffff pref]
  41. For printing struct resources. The 'R' and 'r' specifiers result in a
  42. printed resource with ('R') or without ('r') a decoded flags member.
  43. Physical addresses:
  44. %pa 0x01234567 or 0x0123456789abcdef
  45. For printing a phys_addr_t type (and its derivatives, such as
  46. resource_size_t) which can vary based on build options, regardless of
  47. the width of the CPU data path. Passed by reference.
  48. Raw buffer as a hex string:
  49. %*ph 00 01 02 ... 3f
  50. %*phC 00:01:02: ... :3f
  51. %*phD 00-01-02- ... -3f
  52. %*phN 000102 ... 3f
  53. For printing a small buffers (up to 64 bytes long) as a hex string with
  54. certain separator. For the larger buffers consider to use
  55. print_hex_dump().
  56. MAC/FDDI addresses:
  57. %pM 00:01:02:03:04:05
  58. %pMR 05:04:03:02:01:00
  59. %pMF 00-01-02-03-04-05
  60. %pm 000102030405
  61. %pmR 050403020100
  62. For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
  63. specifiers result in a printed address with ('M') or without ('m') byte
  64. separators. The default byte separator is the colon (':').
  65. Where FDDI addresses are concerned the 'F' specifier can be used after
  66. the 'M' specifier to use dash ('-') separators instead of the default
  67. separator.
  68. For Bluetooth addresses the 'R' specifier shall be used after the 'M'
  69. specifier to use reversed byte order suitable for visual interpretation
  70. of Bluetooth addresses which are in the little endian order.
  71. IPv4 addresses:
  72. %pI4 1.2.3.4
  73. %pi4 001.002.003.004
  74. %p[Ii][hnbl]
  75. For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
  76. specifiers result in a printed address with ('i4') or without ('I4')
  77. leading zeros.
  78. The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
  79. host, network, big or little endian order addresses respectively. Where
  80. no specifier is provided the default network/big endian order is used.
  81. IPv6 addresses:
  82. %pI6 0001:0002:0003:0004:0005:0006:0007:0008
  83. %pi6 00010002000300040005000600070008
  84. %pI6c 1:2:3:4:5:6:7:8
  85. For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
  86. specifiers result in a printed address with ('I6') or without ('i6')
  87. colon-separators. Leading zeros are always used.
  88. The additional 'c' specifier can be used with the 'I' specifier to
  89. print a compressed IPv6 address as described by
  90. http://tools.ietf.org/html/rfc5952
  91. UUID/GUID addresses:
  92. %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
  93. %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
  94. %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
  95. %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
  96. For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
  97. 'b' and 'B' specifiers are used to specify a little endian order in
  98. lower ('l') or upper case ('L') hex characters - and big endian order
  99. in lower ('b') or upper case ('B') hex characters.
  100. Where no additional specifiers are used the default little endian
  101. order with lower case hex characters will be printed.
  102. struct va_format:
  103. %pV
  104. For printing struct va_format structures. These contain a format string
  105. and va_list as follows:
  106. struct va_format {
  107. const char *fmt;
  108. va_list *va;
  109. };
  110. Do not use this feature without some mechanism to verify the
  111. correctness of the format string and va_list arguments.
  112. u64 SHOULD be printed with %llu/%llx, (unsigned long long):
  113. printk("%llu", (unsigned long long)u64_var);
  114. s64 SHOULD be printed with %lld/%llx, (long long):
  115. printk("%lld", (long long)s64_var);
  116. If <type> is dependent on a config option for its size (e.g., sector_t,
  117. blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
  118. format specifier of its largest possible type and explicitly cast to it.
  119. Example:
  120. printk("test: sector number/total blocks: %llu/%llu\n",
  121. (unsigned long long)sector, (unsigned long long)blockcount);
  122. Reminder: sizeof() result is of type size_t.
  123. Thank you for your cooperation and attention.
  124. By Randy Dunlap <rdunlap@xenotime.net> and
  125. Andrew Murray <amurray@mpc-data.co.uk>