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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
12 Raw pointer value SHOULD be printed with %p. The kernel supports
13 the following extended format specifiers for pointer types:
14
15 Symbols/Function Pointers:
16
17 %pF versatile_init+0x0/0x110
18 %pf versatile_init
19 %pS versatile_init+0x0/0x110
20 %ps versatile_init
21 %pB prev_fn_of_versatile_init+0x88/0x88
22
23 For printing symbols and function pointers. The 'S' and 's' specifiers
24 result in the symbol name with ('S') or without ('s') offsets. Where
25 this is used on a kernel without KALLSYMS - the symbol address is
26 printed instead.
27
28 The 'B' specifier results in the symbol name with offsets and should be
29 used when printing stack backtraces. The specifier takes into
30 consideration the effect of compiler optimisations which may occur
31 when tail-call's are used and marked with the noreturn GCC attribute.
32
33 On ia64, ppc64 and parisc64 architectures function pointers are
34 actually function descriptors which must first be resolved. The 'F' and
35 'f' specifiers perform this resolution and then provide the same
36 functionality as the 'S' and 's' specifiers.
37
38 Kernel Pointers:
39
40 %pK 0x01234567 or 0x0123456789abcdef
41
42 For printing kernel pointers which should be hidden from unprivileged
43 users. The behaviour of %pK depends on the kptr_restrict sysctl - see
44 Documentation/sysctl/kernel.txt for more details.
45
46 Struct Resources:
47
48 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
49 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
50 %pR [mem 0x60000000-0x6fffffff pref] or
51 [mem 0x0000000060000000-0x000000006fffffff pref]
52
53 For printing struct resources. The 'R' and 'r' specifiers result in a
54 printed resource with ('R') or without ('r') a decoded flags member.
55
56 Physical addresses:
57
58 %pa 0x01234567 or 0x0123456789abcdef
59
60 For printing a phys_addr_t type (and its derivatives, such as
61 resource_size_t) which can vary based on build options, regardless of
62 the width of the CPU data path. Passed by reference.
63
64 Raw buffer as a hex string:
65 %*ph 00 01 02 ... 3f
66 %*phC 00:01:02: ... :3f
67 %*phD 00-01-02- ... -3f
68 %*phN 000102 ... 3f
69
70 For printing a small buffers (up to 64 bytes long) as a hex string with
71 certain separator. For the larger buffers consider to use
72 print_hex_dump().
73
74 MAC/FDDI addresses:
75
76 %pM 00:01:02:03:04:05
77 %pMR 05:04:03:02:01:00
78 %pMF 00-01-02-03-04-05
79 %pm 000102030405
80 %pmR 050403020100
81
82 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
83 specifiers result in a printed address with ('M') or without ('m') byte
84 separators. The default byte separator is the colon (':').
85
86 Where FDDI addresses are concerned the 'F' specifier can be used after
87 the 'M' specifier to use dash ('-') separators instead of the default
88 separator.
89
90 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
91 specifier to use reversed byte order suitable for visual interpretation
92 of Bluetooth addresses which are in the little endian order.
93
94 IPv4 addresses:
95
96 %pI4 1.2.3.4
97 %pi4 001.002.003.004
98 %p[Ii][hnbl]
99
100 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
101 specifiers result in a printed address with ('i4') or without ('I4')
102 leading zeros.
103
104 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
105 host, network, big or little endian order addresses respectively. Where
106 no specifier is provided the default network/big endian order is used.
107
108 IPv6 addresses:
109
110 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
111 %pi6 00010002000300040005000600070008
112 %pI6c 1:2:3:4:5:6:7:8
113
114 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
115 specifiers result in a printed address with ('I6') or without ('i6')
116 colon-separators. Leading zeros are always used.
117
118 The additional 'c' specifier can be used with the 'I' specifier to
119 print a compressed IPv6 address as described by
120 http://tools.ietf.org/html/rfc5952
121
122 UUID/GUID addresses:
123
124 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
125 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
126 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
127 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
128
129 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
130 'b' and 'B' specifiers are used to specify a little endian order in
131 lower ('l') or upper case ('L') hex characters - and big endian order
132 in lower ('b') or upper case ('B') hex characters.
133
134 Where no additional specifiers are used the default little endian
135 order with lower case hex characters will be printed.
136
137 struct va_format:
138
139 %pV
140
141 For printing struct va_format structures. These contain a format string
142 and va_list as follows:
143
144 struct va_format {
145 const char *fmt;
146 va_list *va;
147 };
148
149 Do not use this feature without some mechanism to verify the
150 correctness of the format string and va_list arguments.
151
152 u64 SHOULD be printed with %llu/%llx, (unsigned long long):
153
154 printk("%llu", (unsigned long long)u64_var);
155
156 s64 SHOULD be printed with %lld/%llx, (long long):
157
158 printk("%lld", (long long)s64_var);
159
160 If <type> is dependent on a config option for its size (e.g., sector_t,
161 blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
162 format specifier of its largest possible type and explicitly cast to it.
163 Example:
164
165 printk("test: sector number/total blocks: %llu/%llu\n",
166 (unsigned long long)sector, (unsigned long long)blockcount);
167
168 Reminder: sizeof() result is of type size_t.
169
170 Thank you for your cooperation and attention.
171
172
173 By Randy Dunlap <rdunlap@xenotime.net> and
174 Andrew Murray <amurray@mpc-data.co.uk>