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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 Shevchenko31550a12012-07-30 14:40:27 -070073Raw buffer as a hex string:
74 %*ph 00 01 02 ... 3f
75 %*phC 00:01:02: ... :3f
76 %*phD 00-01-02- ... -3f
77 %*phN 000102 ... 3f
78
79 For printing a small buffers (up to 64 bytes long) as a hex string with
80 certain separator. For the larger buffers consider to use
81 print_hex_dump().
82
Andrew Murray04c55712011-06-15 12:57:09 -070083MAC/FDDI addresses:
84
85 %pM 00:01:02:03:04:05
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070086 %pMR 05:04:03:02:01:00
Andrew Murray04c55712011-06-15 12:57:09 -070087 %pMF 00-01-02-03-04-05
88 %pm 000102030405
Andy Shevchenko7c591542012-10-04 17:12:33 -070089 %pmR 050403020100
Andrew Murray04c55712011-06-15 12:57:09 -070090
91 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
92 specifiers result in a printed address with ('M') or without ('m') byte
93 separators. The default byte separator is the colon (':').
94
95 Where FDDI addresses are concerned the 'F' specifier can be used after
96 the 'M' specifier to use dash ('-') separators instead of the default
97 separator.
98
Andrei Emeltchenko76597ff92012-07-30 14:40:23 -070099 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
100 specifier to use reversed byte order suitable for visual interpretation
101 of Bluetooth addresses which are in the little endian order.
102
Andrew Murray04c55712011-06-15 12:57:09 -0700103IPv4 addresses:
104
105 %pI4 1.2.3.4
106 %pi4 001.002.003.004
Daniel Borkmann8ecada12013-06-28 15:49:39 +0200107 %p[Ii]4[hnbl]
Andrew Murray04c55712011-06-15 12:57:09 -0700108
109 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
110 specifiers result in a printed address with ('i4') or without ('I4')
111 leading zeros.
112
113 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
114 host, network, big or little endian order addresses respectively. Where
115 no specifier is provided the default network/big endian order is used.
116
117IPv6 addresses:
118
119 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
120 %pi6 00010002000300040005000600070008
121 %pI6c 1:2:3:4:5:6:7:8
122
123 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
124 specifiers result in a printed address with ('I6') or without ('i6')
125 colon-separators. Leading zeros are always used.
126
127 The additional 'c' specifier can be used with the 'I' specifier to
128 print a compressed IPv6 address as described by
129 http://tools.ietf.org/html/rfc5952
130
Daniel Borkmann10679642013-06-28 19:49:39 +0200131IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
132
133 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
134 %piS 001.002.003.004 or 00010002000300040005000600070008
135 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
136 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
137 %p[Ii]S[pfschnbl]
138
139 For printing an IP address without the need to distinguish whether it's
140 of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
141 specified through 'IS' or 'iS', can be passed to this format specifier.
142
143 The additional 'p', 'f', and 's' specifiers are used to specify port
144 (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
145 flowinfo a '/' and scope a '%', each followed by the actual value.
146
147 In case of an IPv6 address the compressed IPv6 address as described by
148 http://tools.ietf.org/html/rfc5952 is being used if the additional
149 specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
150 case of additional specifiers 'p', 'f' or 's' as suggested by
151 https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
152
153 In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
154 specifiers can be used as well and are ignored in case of an IPv6
155 address.
156
157 Further examples:
158
159 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
160 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
161 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
162
Andrew Murray04c55712011-06-15 12:57:09 -0700163UUID/GUID addresses:
164
165 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
166 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
167 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
168 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
169
170 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
171 'b' and 'B' specifiers are used to specify a little endian order in
172 lower ('l') or upper case ('L') hex characters - and big endian order
173 in lower ('b') or upper case ('B') hex characters.
174
175 Where no additional specifiers are used the default little endian
176 order with lower case hex characters will be printed.
177
Al Viro4b6ccca2013-09-03 12:00:44 -0400178dentry names:
179 %pd{,2,3,4}
180 %pD{,2,3,4}
181
182 For printing dentry name; if we race with d_move(), the name might be
183 a mix of old and new ones, but it won't oops. %pd dentry is a safer
184 equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
185 n last components. %pD does the same thing for struct file.
186
Andrew Murray04c55712011-06-15 12:57:09 -0700187struct va_format:
188
189 %pV
190
191 For printing struct va_format structures. These contain a format string
192 and va_list as follows:
193
194 struct va_format {
195 const char *fmt;
196 va_list *va;
197 };
198
199 Do not use this feature without some mechanism to verify the
200 correctness of the format string and va_list arguments.
Randy Dunlapb67ad182008-11-12 13:26:55 -0800201
202u64 SHOULD be printed with %llu/%llx, (unsigned long long):
203
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700204 printk("%llu", u64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800205
206s64 SHOULD be printed with %lld/%llx, (long long):
207
Geert Uytterhoeven2a7930b2013-08-20 14:07:23 -0700208 printk("%lld", s64_var);
Randy Dunlapb67ad182008-11-12 13:26:55 -0800209
210If <type> is dependent on a config option for its size (e.g., sector_t,
Stepan Moskovchenko7d799212013-02-21 16:43:09 -0800211blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
212format specifier of its largest possible type and explicitly cast to it.
213Example:
Randy Dunlapb67ad182008-11-12 13:26:55 -0800214
215 printk("test: sector number/total blocks: %llu/%llu\n",
216 (unsigned long long)sector, (unsigned long long)blockcount);
217
218Reminder: sizeof() result is of type size_t.
219
220Thank you for your cooperation and attention.
221
222
Randy Dunlap755727b2013-03-08 12:43:35 -0800223By Randy Dunlap <rdunlap@infradead.org> and
Andrew Murray04c55712011-06-15 12:57:09 -0700224Andrew Murray <amurray@mpc-data.co.uk>