blob: 445ad743ec814ee4571c175884d3ccce4ffda11a [file] [log] [blame]
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
Joe Perchesb0d33c22012-12-12 10:18:50 -080020 %pSR versatile_init+0x9/0x110
21 (with __builtin_extract_return_addr() translation)
Andrew Murray04c55712011-06-15 12:57:09 -070022 %ps versatile_init
23 %pB prev_fn_of_versatile_init+0x88/0x88
24
25 For printing symbols and function pointers. The 'S' and 's' specifiers
26 result in the symbol name with ('S') or without ('s') offsets. Where
27 this is used on a kernel without KALLSYMS - the symbol address is
28 printed instead.
29
30 The 'B' specifier results in the symbol name with offsets and should be
31 used when printing stack backtraces. The specifier takes into
32 consideration the effect of compiler optimisations which may occur
33 when tail-call's are used and marked with the noreturn GCC attribute.
34
35 On ia64, ppc64 and parisc64 architectures function pointers are
36 actually function descriptors which must first be resolved. The 'F' and
37 'f' specifiers perform this resolution and then provide the same
38 functionality as the 'S' and 's' specifiers.
39
40Kernel Pointers:
41
42 %pK 0x01234567 or 0x0123456789abcdef
43
44 For printing kernel pointers which should be hidden from unprivileged
45 users. The behaviour of %pK depends on the kptr_restrict sysctl - see
46 Documentation/sysctl/kernel.txt for more details.
47
48Struct Resources:
49
50 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
51 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
52 %pR [mem 0x60000000-0x6fffffff pref] or
53 [mem 0x0000000060000000-0x000000006fffffff pref]
54
55 For printing struct resources. The 'R' and 'r' specifiers result in a
56 printed resource with ('R') or without ('r') a decoded flags member.
57
Stepan Moskovchenko7d799212013-02-21 16:43:09 -080058Physical addresses:
59
60 %pa 0x01234567 or 0x0123456789abcdef
61
62 For printing a phys_addr_t type (and its derivatives, such as
63 resource_size_t) which can vary based on build options, regardless of
64 the width of the CPU data path. Passed by reference.
65
Andy Shevchenko31550a12012-07-30 14:40:27 -070066Raw buffer as a hex string:
67 %*ph 00 01 02 ... 3f
68 %*phC 00:01:02: ... :3f
69 %*phD 00-01-02- ... -3f
70 %*phN 000102 ... 3f
71
72 For printing a small buffers (up to 64 bytes long) as a hex string with
73 certain separator. For the larger buffers consider to use
74 print_hex_dump().
75
Andrew Murray04c55712011-06-15 12:57:09 -070076MAC/FDDI addresses:
77
78 %pM 00:01:02:03:04:05
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070079 %pMR 05:04:03:02:01:00
Andrew Murray04c55712011-06-15 12:57:09 -070080 %pMF 00-01-02-03-04-05
81 %pm 000102030405
Andy Shevchenko7c591542012-10-04 17:12:33 -070082 %pmR 050403020100
Andrew Murray04c55712011-06-15 12:57:09 -070083
84 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
85 specifiers result in a printed address with ('M') or without ('m') byte
86 separators. The default byte separator is the colon (':').
87
88 Where FDDI addresses are concerned the 'F' specifier can be used after
89 the 'M' specifier to use dash ('-') separators instead of the default
90 separator.
91
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070092 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
93 specifier to use reversed byte order suitable for visual interpretation
94 of Bluetooth addresses which are in the little endian order.
95
Andrew Murray04c55712011-06-15 12:57:09 -070096IPv4 addresses:
97
98 %pI4 1.2.3.4
99 %pi4 001.002.003.004
Daniel Borkmann8ecada12013-06-28 15:49:39 +0200100 %p[Ii]4[hnbl]
Andrew Murray04c55712011-06-15 12:57:09 -0700101
102 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
103 specifiers result in a printed address with ('i4') or without ('I4')
104 leading zeros.
105
106 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
107 host, network, big or little endian order addresses respectively. Where
108 no specifier is provided the default network/big endian order is used.
109
110IPv6 addresses:
111
112 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
113 %pi6 00010002000300040005000600070008
114 %pI6c 1:2:3:4:5:6:7:8
115
116 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
117 specifiers result in a printed address with ('I6') or without ('i6')
118 colon-separators. Leading zeros are always used.
119
120 The additional 'c' specifier can be used with the 'I' specifier to
121 print a compressed IPv6 address as described by
122 http://tools.ietf.org/html/rfc5952
123
Daniel Borkmann10679642013-06-28 19:49:39 +0200124IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
125
126 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
127 %piS 001.002.003.004 or 00010002000300040005000600070008
128 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
129 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
130 %p[Ii]S[pfschnbl]
131
132 For printing an IP address without the need to distinguish whether it's
133 of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
134 specified through 'IS' or 'iS', can be passed to this format specifier.
135
136 The additional 'p', 'f', and 's' specifiers are used to specify port
137 (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
138 flowinfo a '/' and scope a '%', each followed by the actual value.
139
140 In case of an IPv6 address the compressed IPv6 address as described by
141 http://tools.ietf.org/html/rfc5952 is being used if the additional
142 specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
143 case of additional specifiers 'p', 'f' or 's' as suggested by
144 https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
145
146 In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
147 specifiers can be used as well and are ignored in case of an IPv6
148 address.
149
150 Further examples:
151
152 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
153 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
154 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
155
Andrew Murray04c55712011-06-15 12:57:09 -0700156UUID/GUID addresses:
157
158 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
159 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
160 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
161 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
162
163 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
164 'b' and 'B' specifiers are used to specify a little endian order in
165 lower ('l') or upper case ('L') hex characters - and big endian order
166 in lower ('b') or upper case ('B') hex characters.
167
168 Where no additional specifiers are used the default little endian
169 order with lower case hex characters will be printed.
170
Al Viro4b6ccca2013-09-03 12:00:44 -0400171dentry names:
172 %pd{,2,3,4}
173 %pD{,2,3,4}
174
175 For printing dentry name; if we race with d_move(), the name might be
176 a mix of old and new ones, but it won't oops. %pd dentry is a safer
177 equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
178 n last components. %pD does the same thing for struct file.
179
Andrew Murray04c55712011-06-15 12:57:09 -0700180struct va_format:
181
182 %pV
183
184 For printing struct va_format structures. These contain a format string
185 and va_list as follows:
186
187 struct va_format {
188 const char *fmt;
189 va_list *va;
190 };
191
192 Do not use this feature without some mechanism to verify the
193 correctness of the format string and va_list arguments.
Randy Dunlapb67ad182008-11-12 13:26:55 -0800194
195u64 SHOULD be printed with %llu/%llx, (unsigned long long):
196
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700197 printk("%llu", u64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800198
199s64 SHOULD be printed with %lld/%llx, (long long):
200
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700201 printk("%lld", s64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800202
203If <type> is dependent on a config option for its size (e.g., sector_t,
Stepan Moskovchenko7d799212013-02-21 16:43:09 -0800204blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
205format specifier of its largest possible type and explicitly cast to it.
206Example:
Randy Dunlapb67ad182008-11-12 13:26:55 -0800207
208 printk("test: sector number/total blocks: %llu/%llu\n",
209 (unsigned long long)sector, (unsigned long long)blockcount);
210
211Reminder: sizeof() result is of type size_t.
212
213Thank you for your cooperation and attention.
214
215
Randy Dunlap755727b2013-03-08 12:43:35 -0800216By Randy Dunlap <rdunlap@infradead.org> and
Andrew Murray04c55712011-06-15 12:57:09 -0700217Andrew Murray <amurray@mpc-data.co.uk>