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b67ad18b RD |
1 | If 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 | ||
04c55715 AM |
12 | Raw pointer value SHOULD be printed with %p. The kernel supports |
13 | the following extended format specifiers for pointer types: | |
14 | ||
15 | Symbols/Function Pointers: | |
16 | ||
17 | %pF versatile_init+0x0/0x110 | |
18 | %pf versatile_init | |
19 | %pS versatile_init+0x0/0x110 | |
b0d33c2b JP |
20 | %pSR versatile_init+0x9/0x110 |
21 | (with __builtin_extract_return_addr() translation) | |
04c55715 AM |
22 | %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 | ||
40 | Kernel 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 | ||
48 | Struct 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 | ||
aaf07621 | 58 | Physical addresses types phys_addr_t: |
7d799210 | 59 | |
aaf07621 | 60 | %pa[p] 0x01234567 or 0x0123456789abcdef |
7d799210 SM |
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 | ||
aaf07621 JP |
66 | DMA 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 | ||
31550a16 AS |
73 | Raw 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 | ||
04c55715 AM |
83 | MAC/FDDI addresses: |
84 | ||
85 | %pM 00:01:02:03:04:05 | |
76597ff9 | 86 | %pMR 05:04:03:02:01:00 |
04c55715 AM |
87 | %pMF 00-01-02-03-04-05 |
88 | %pm 000102030405 | |
7c59154e | 89 | %pmR 050403020100 |
04c55715 AM |
90 | |
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 | ||
76597ff9 AE |
99 | 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 | ||
04c55715 AM |
103 | IPv4 addresses: |
104 | ||
105 | %pI4 1.2.3.4 | |
106 | %pi4 001.002.003.004 | |
8ecada16 | 107 | %p[Ii]4[hnbl] |
04c55715 AM |
108 | |
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 | ||
117 | IPv6 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 | ||
10679643 DB |
131 | IPv4/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 | ||
04c55715 AM |
163 | UUID/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 | ||
4b6ccca7 AV |
178 | dentry 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 | ||
04c55715 AM |
187 | struct 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. | |
b67ad18b RD |
201 | |
202 | u64 SHOULD be printed with %llu/%llx, (unsigned long long): | |
203 | ||
2a7930bd | 204 | printk("%llu", u64_var); |
b67ad18b RD |
205 | |
206 | s64 SHOULD be printed with %lld/%llx, (long long): | |
207 | ||
2a7930bd | 208 | printk("%lld", s64_var); |
b67ad18b RD |
209 | |
210 | If <type> is dependent on a config option for its size (e.g., sector_t, | |
7d799210 SM |
211 | blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a |
212 | format specifier of its largest possible type and explicitly cast to it. | |
213 | Example: | |
b67ad18b RD |
214 | |
215 | printk("test: sector number/total blocks: %llu/%llu\n", | |
216 | (unsigned long long)sector, (unsigned long long)blockcount); | |
217 | ||
218 | Reminder: sizeof() result is of type size_t. | |
219 | ||
220 | Thank you for your cooperation and attention. | |
221 | ||
222 | ||
755727b7 | 223 | By Randy Dunlap <rdunlap@infradead.org> and |
04c55715 | 224 | Andrew Murray <amurray@mpc-data.co.uk> |