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Randy Dunlapb67ad182008-11-12 13:26:55 -08001If 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
Andrew Murray04c55712011-06-15 12:57:09 -070012Raw pointer value SHOULD be printed with %p. The kernel supports
13the following extended format specifiers for pointer types:
14
15Symbols/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
38Kernel 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
46Struct 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
Andy Shevchenko31550a12012-07-30 14:40:27 -070056Raw buffer as a hex string:
57 %*ph 00 01 02 ... 3f
58 %*phC 00:01:02: ... :3f
59 %*phD 00-01-02- ... -3f
60 %*phN 000102 ... 3f
61
62 For printing a small buffers (up to 64 bytes long) as a hex string with
63 certain separator. For the larger buffers consider to use
64 print_hex_dump().
65
Andrew Murray04c55712011-06-15 12:57:09 -070066MAC/FDDI addresses:
67
68 %pM 00:01:02:03:04:05
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070069 %pMR 05:04:03:02:01:00
Andrew Murray04c55712011-06-15 12:57:09 -070070 %pMF 00-01-02-03-04-05
71 %pm 000102030405
72
73 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
74 specifiers result in a printed address with ('M') or without ('m') byte
75 separators. The default byte separator is the colon (':').
76
77 Where FDDI addresses are concerned the 'F' specifier can be used after
78 the 'M' specifier to use dash ('-') separators instead of the default
79 separator.
80
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070081 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
82 specifier to use reversed byte order suitable for visual interpretation
83 of Bluetooth addresses which are in the little endian order.
84
Andrew Murray04c55712011-06-15 12:57:09 -070085IPv4 addresses:
86
87 %pI4 1.2.3.4
88 %pi4 001.002.003.004
89 %p[Ii][hnbl]
90
91 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
92 specifiers result in a printed address with ('i4') or without ('I4')
93 leading zeros.
94
95 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
96 host, network, big or little endian order addresses respectively. Where
97 no specifier is provided the default network/big endian order is used.
98
99IPv6 addresses:
100
101 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
102 %pi6 00010002000300040005000600070008
103 %pI6c 1:2:3:4:5:6:7:8
104
105 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
106 specifiers result in a printed address with ('I6') or without ('i6')
107 colon-separators. Leading zeros are always used.
108
109 The additional 'c' specifier can be used with the 'I' specifier to
110 print a compressed IPv6 address as described by
111 http://tools.ietf.org/html/rfc5952
112
113UUID/GUID addresses:
114
115 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
116 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
117 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
118 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
119
120 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
121 'b' and 'B' specifiers are used to specify a little endian order in
122 lower ('l') or upper case ('L') hex characters - and big endian order
123 in lower ('b') or upper case ('B') hex characters.
124
125 Where no additional specifiers are used the default little endian
126 order with lower case hex characters will be printed.
127
128struct va_format:
129
130 %pV
131
132 For printing struct va_format structures. These contain a format string
133 and va_list as follows:
134
135 struct va_format {
136 const char *fmt;
137 va_list *va;
138 };
139
140 Do not use this feature without some mechanism to verify the
141 correctness of the format string and va_list arguments.
Randy Dunlapb67ad182008-11-12 13:26:55 -0800142
143u64 SHOULD be printed with %llu/%llx, (unsigned long long):
144
145 printk("%llu", (unsigned long long)u64_var);
146
147s64 SHOULD be printed with %lld/%llx, (long long):
148
149 printk("%lld", (long long)s64_var);
150
151If <type> is dependent on a config option for its size (e.g., sector_t,
152blkcnt_t, phys_addr_t, resource_size_t) or is architecture-dependent
153for its size (e.g., tcflag_t), use a format specifier of its largest
154possible type and explicitly cast to it. Example:
155
156 printk("test: sector number/total blocks: %llu/%llu\n",
157 (unsigned long long)sector, (unsigned long long)blockcount);
158
159Reminder: sizeof() result is of type size_t.
160
161Thank you for your cooperation and attention.
162
163
Andrew Murray04c55712011-06-15 12:57:09 -0700164By Randy Dunlap <rdunlap@xenotime.net> and
165Andrew Murray <amurray@mpc-data.co.uk>