tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1If 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
12Raw 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
56Raw 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
66MAC/FDDI addresses:
67
68 %pM 00:01:02:03:04:05
69 %pMR 05:04:03:02:01:00
70 %pMF 00-01-02-03-04-05
71 %pm 000102030405
72 %pmR 050403020100
73
74 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
75 specifiers result in a printed address with ('M') or without ('m') byte
76 separators. The default byte separator is the colon (':').
77
78 Where FDDI addresses are concerned the 'F' specifier can be used after
79 the 'M' specifier to use dash ('-') separators instead of the default
80 separator.
81
82 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
83 specifier to use reversed byte order suitable for visual interpretation
84 of Bluetooth addresses which are in the little endian order.
85
86IPv4 addresses:
87
88 %pI4 1.2.3.4
89 %pi4 001.002.003.004
90 %p[Ii][hnbl]
91
92 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
93 specifiers result in a printed address with ('i4') or without ('I4')
94 leading zeros.
95
96 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
97 host, network, big or little endian order addresses respectively. Where
98 no specifier is provided the default network/big endian order is used.
99
100IPv6 addresses:
101
102 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
103 %pi6 00010002000300040005000600070008
104 %pI6c 1:2:3:4:5:6:7:8
105
106 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
107 specifiers result in a printed address with ('I6') or without ('i6')
108 colon-separators. Leading zeros are always used.
109
110 The additional 'c' specifier can be used with the 'I' specifier to
111 print a compressed IPv6 address as described by
112 http://tools.ietf.org/html/rfc5952
113
114UUID/GUID addresses:
115
116 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
117 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
118 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
119 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
120
121 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
122 'b' and 'B' specifiers are used to specify a little endian order in
123 lower ('l') or upper case ('L') hex characters - and big endian order
124 in lower ('b') or upper case ('B') hex characters.
125
126 Where no additional specifiers are used the default little endian
127 order with lower case hex characters will be printed.
128
129struct va_format:
130
131 %pV
132
133 For printing struct va_format structures. These contain a format string
134 and va_list as follows:
135
136 struct va_format {
137 const char *fmt;
138 va_list *va;
139 };
140
141 Do not use this feature without some mechanism to verify the
142 correctness of the format string and va_list arguments.
143
144u64 SHOULD be printed with %llu/%llx, (unsigned long long):
145
146 printk("%llu", (unsigned long long)u64_var);
147
148s64 SHOULD be printed with %lld/%llx, (long long):
149
150 printk("%lld", (long long)s64_var);
151
152If <type> is dependent on a config option for its size (e.g., sector_t,
153blkcnt_t, phys_addr_t, resource_size_t) or is architecture-dependent
154for its size (e.g., tcflag_t), use a format specifier of its largest
155possible type and explicitly cast to it. Example:
156
157 printk("test: sector number/total blocks: %llu/%llu\n",
158 (unsigned long long)sector, (unsigned long long)blockcount);
159
160Reminder: sizeof() result is of type size_t.
161
162Thank you for your cooperation and attention.
163
164
165By Randy Dunlap <rdunlap@xenotime.net> and
166Andrew Murray <amurray@mpc-data.co.uk>