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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
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
Joe Perchesaaf07622014-01-23 15:54:17 -080058Physical addresses types phys_addr_t:
Stepan Moskovchenko7d799212013-02-21 16:43:09 -080059
Joe Perchesaaf07622014-01-23 15:54:17 -080060 %pa[p] 0x01234567 or 0x0123456789abcdef
Stepan Moskovchenko7d799212013-02-21 16:43:09 -080061
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
Joe Perchesaaf07622014-01-23 15:54:17 -080066DMA addresses types dma_addr_t:
67
68 %pad 0x01234567 or 0x0123456789abcdef
69
70 For printing a dma_addr_t type which can vary based on build options,
71 regardless of the width of the CPU data path. Passed by reference.
72
Andy Shevchenko71dca952014-10-13 15:55:18 -070073Raw buffer as an escaped string:
74
75 %*pE[achnops]
76
77 For printing raw buffer as an escaped string. For the following buffer
78
79 1b 62 20 5c 43 07 22 90 0d 5d
80
81 few examples show how the conversion would be done (the result string
82 without surrounding quotes):
83
84 %*pE "\eb \C\a"\220\r]"
85 %*pEhp "\x1bb \C\x07"\x90\x0d]"
86 %*pEa "\e\142\040\\\103\a\042\220\r\135"
87
88 The conversion rules are applied according to an optional combination
89 of flags (see string_escape_mem() kernel documentation for the
90 details):
91 a - ESCAPE_ANY
92 c - ESCAPE_SPECIAL
93 h - ESCAPE_HEX
94 n - ESCAPE_NULL
95 o - ESCAPE_OCTAL
96 p - ESCAPE_NP
97 s - ESCAPE_SPACE
98 By default ESCAPE_ANY_NP is used.
99
100 ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
101 printing SSIDs.
102
103 If field width is omitted the 1 byte only will be escaped.
104
Andy Shevchenko31550a12012-07-30 14:40:27 -0700105Raw buffer as a hex string:
106 %*ph 00 01 02 ... 3f
107 %*phC 00:01:02: ... :3f
108 %*phD 00-01-02- ... -3f
109 %*phN 000102 ... 3f
110
111 For printing a small buffers (up to 64 bytes long) as a hex string with
112 certain separator. For the larger buffers consider to use
113 print_hex_dump().
114
Andrew Murray04c55712011-06-15 12:57:09 -0700115MAC/FDDI addresses:
116
117 %pM 00:01:02:03:04:05
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -0700118 %pMR 05:04:03:02:01:00
Andrew Murray04c55712011-06-15 12:57:09 -0700119 %pMF 00-01-02-03-04-05
120 %pm 000102030405
Andy Shevchenko7c591542012-10-04 17:12:33 -0700121 %pmR 050403020100
Andrew Murray04c55712011-06-15 12:57:09 -0700122
123 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
124 specifiers result in a printed address with ('M') or without ('m') byte
125 separators. The default byte separator is the colon (':').
126
127 Where FDDI addresses are concerned the 'F' specifier can be used after
128 the 'M' specifier to use dash ('-') separators instead of the default
129 separator.
130
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -0700131 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
132 specifier to use reversed byte order suitable for visual interpretation
133 of Bluetooth addresses which are in the little endian order.
134
Andrew Murray04c55712011-06-15 12:57:09 -0700135IPv4 addresses:
136
137 %pI4 1.2.3.4
138 %pi4 001.002.003.004
Daniel Borkmann8ecada12013-06-28 15:49:39 +0200139 %p[Ii]4[hnbl]
Andrew Murray04c55712011-06-15 12:57:09 -0700140
141 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
142 specifiers result in a printed address with ('i4') or without ('I4')
143 leading zeros.
144
145 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
146 host, network, big or little endian order addresses respectively. Where
147 no specifier is provided the default network/big endian order is used.
148
149IPv6 addresses:
150
151 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
152 %pi6 00010002000300040005000600070008
153 %pI6c 1:2:3:4:5:6:7:8
154
155 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
156 specifiers result in a printed address with ('I6') or without ('i6')
157 colon-separators. Leading zeros are always used.
158
159 The additional 'c' specifier can be used with the 'I' specifier to
160 print a compressed IPv6 address as described by
161 http://tools.ietf.org/html/rfc5952
162
Daniel Borkmann10679642013-06-28 19:49:39 +0200163IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
164
165 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
166 %piS 001.002.003.004 or 00010002000300040005000600070008
167 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
168 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
169 %p[Ii]S[pfschnbl]
170
171 For printing an IP address without the need to distinguish whether it's
172 of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
173 specified through 'IS' or 'iS', can be passed to this format specifier.
174
175 The additional 'p', 'f', and 's' specifiers are used to specify port
176 (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
177 flowinfo a '/' and scope a '%', each followed by the actual value.
178
179 In case of an IPv6 address the compressed IPv6 address as described by
180 http://tools.ietf.org/html/rfc5952 is being used if the additional
181 specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
182 case of additional specifiers 'p', 'f' or 's' as suggested by
183 https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
184
185 In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
186 specifiers can be used as well and are ignored in case of an IPv6
187 address.
188
189 Further examples:
190
191 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
192 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
193 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
194
Andrew Murray04c55712011-06-15 12:57:09 -0700195UUID/GUID addresses:
196
197 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
198 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
199 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
200 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
201
202 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
203 'b' and 'B' specifiers are used to specify a little endian order in
204 lower ('l') or upper case ('L') hex characters - and big endian order
205 in lower ('b') or upper case ('B') hex characters.
206
207 Where no additional specifiers are used the default little endian
208 order with lower case hex characters will be printed.
209
Al Viro4b6ccca2013-09-03 12:00:44 -0400210dentry names:
211 %pd{,2,3,4}
212 %pD{,2,3,4}
213
214 For printing dentry name; if we race with d_move(), the name might be
215 a mix of old and new ones, but it won't oops. %pd dentry is a safer
216 equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
217 n last components. %pD does the same thing for struct file.
218
Andrew Murray04c55712011-06-15 12:57:09 -0700219struct va_format:
220
221 %pV
222
223 For printing struct va_format structures. These contain a format string
224 and va_list as follows:
225
226 struct va_format {
227 const char *fmt;
228 va_list *va;
229 };
230
231 Do not use this feature without some mechanism to verify the
232 correctness of the format string and va_list arguments.
Randy Dunlapb67ad182008-11-12 13:26:55 -0800233
Ilya Dryomov15a0b3f2014-04-07 13:43:52 +0400234u64 SHOULD be printed with %llu/%llx:
Randy Dunlapb67ad182008-11-12 13:26:55 -0800235
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700236 printk("%llu", u64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800237
Ilya Dryomov15a0b3f2014-04-07 13:43:52 +0400238s64 SHOULD be printed with %lld/%llx:
Randy Dunlapb67ad182008-11-12 13:26:55 -0800239
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700240 printk("%lld", s64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800241
242If <type> is dependent on a config option for its size (e.g., sector_t,
Stepan Moskovchenko7d799212013-02-21 16:43:09 -0800243blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
244format specifier of its largest possible type and explicitly cast to it.
245Example:
Randy Dunlapb67ad182008-11-12 13:26:55 -0800246
247 printk("test: sector number/total blocks: %llu/%llu\n",
248 (unsigned long long)sector, (unsigned long long)blockcount);
249
250Reminder: sizeof() result is of type size_t.
251
252Thank you for your cooperation and attention.
253
254
Randy Dunlap755727b2013-03-08 12:43:35 -0800255By Randy Dunlap <rdunlap@infradead.org> and
Andrew Murray04c55712011-06-15 12:57:09 -0700256Andrew Murray <amurray@mpc-data.co.uk>