1 If variable is of Type, use printk format specifier:
2 ---------------------------------------------------------
6 unsigned long %lu or %lx
8 unsigned long long %llu or %llx
12 Raw pointer value SHOULD be printed with %p. The kernel supports
13 the following extended format specifiers for pointer types:
15 Symbols/Function Pointers:
17 %pF versatile_init+0x0/0x110
19 %pS versatile_init+0x0/0x110
20 %pSR versatile_init+0x9/0x110
21 (with __builtin_extract_return_addr() translation)
23 %pB prev_fn_of_versatile_init+0x88/0x88
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
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.
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.
42 %pK 0x01234567 or 0x0123456789abcdef
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.
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]
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.
59 Physical addresses types phys_addr_t:
61 %pa[p] 0x01234567 or 0x0123456789abcdef
63 For printing a phys_addr_t type (and its derivatives, such as
64 resource_size_t) which can vary based on build options, regardless of
65 the width of the CPU data path. Passed by reference.
67 DMA addresses types dma_addr_t:
69 %pad 0x01234567 or 0x0123456789abcdef
71 For printing a dma_addr_t type which can vary based on build options,
72 regardless of the width of the CPU data path. Passed by reference.
74 Raw buffer as an escaped string:
78 For printing raw buffer as an escaped string. For the following buffer
80 1b 62 20 5c 43 07 22 90 0d 5d
82 few examples show how the conversion would be done (the result string
83 without surrounding quotes):
85 %*pE "\eb \C\a"\220\r]"
86 %*pEhp "\x1bb \C\x07"\x90\x0d]"
87 %*pEa "\e\142\040\\\103\a\042\220\r\135"
89 The conversion rules are applied according to an optional combination
90 of flags (see string_escape_mem() kernel documentation for the
99 By default ESCAPE_ANY_NP is used.
101 ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
104 If field width is omitted the 1 byte only will be escaped.
106 Raw buffer as a hex string:
108 %*phC 00:01:02: ... :3f
109 %*phD 00-01-02- ... -3f
112 For printing a small buffers (up to 64 bytes long) as a hex string with
113 certain separator. For the larger buffers consider to use
118 %pM 00:01:02:03:04:05
119 %pMR 05:04:03:02:01:00
120 %pMF 00-01-02-03-04-05
124 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
125 specifiers result in a printed address with ('M') or without ('m') byte
126 separators. The default byte separator is the colon (':').
128 Where FDDI addresses are concerned the 'F' specifier can be used after
129 the 'M' specifier to use dash ('-') separators instead of the default
132 For Bluetooth addresses the 'R' specifier shall be used after the 'M'
133 specifier to use reversed byte order suitable for visual interpretation
134 of Bluetooth addresses which are in the little endian order.
144 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
145 specifiers result in a printed address with ('i4') or without ('I4')
148 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
149 host, network, big or little endian order addresses respectively. Where
150 no specifier is provided the default network/big endian order is used.
156 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
157 %pi6 00010002000300040005000600070008
158 %pI6c 1:2:3:4:5:6:7:8
160 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
161 specifiers result in a printed address with ('I6') or without ('i6')
162 colon-separators. Leading zeros are always used.
164 The additional 'c' specifier can be used with the 'I' specifier to
165 print a compressed IPv6 address as described by
166 http://tools.ietf.org/html/rfc5952
170 IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
172 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
173 %piS 001.002.003.004 or 00010002000300040005000600070008
174 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
175 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
178 For printing an IP address without the need to distinguish whether it's
179 of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
180 specified through 'IS' or 'iS', can be passed to this format specifier.
182 The additional 'p', 'f', and 's' specifiers are used to specify port
183 (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
184 flowinfo a '/' and scope a '%', each followed by the actual value.
186 In case of an IPv6 address the compressed IPv6 address as described by
187 http://tools.ietf.org/html/rfc5952 is being used if the additional
188 specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
189 case of additional specifiers 'p', 'f' or 's' as suggested by
190 https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
192 In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
193 specifiers can be used as well and are ignored in case of an IPv6
200 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
201 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
202 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
206 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
207 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
208 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
209 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
211 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
212 'b' and 'B' specifiers are used to specify a little endian order in
213 lower ('l') or upper case ('L') hex characters - and big endian order
214 in lower ('b') or upper case ('B') hex characters.
216 Where no additional specifiers are used the default little endian
217 order with lower case hex characters will be printed.
225 For printing dentry name; if we race with d_move(), the name might be
226 a mix of old and new ones, but it won't oops. %pd dentry is a safer
227 equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
228 n last components. %pD does the same thing for struct file.
236 For printing struct va_format structures. These contain a format string
237 and va_list as follows:
244 Do not use this feature without some mechanism to verify the
245 correctness of the format string and va_list arguments.
249 u64 SHOULD be printed with %llu/%llx:
251 printk("%llu", u64_var);
253 s64 SHOULD be printed with %lld/%llx:
255 printk("%lld", s64_var);
257 If <type> is dependent on a config option for its size (e.g., sector_t,
258 blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
259 format specifier of its largest possible type and explicitly cast to it.
262 printk("test: sector number/total blocks: %llu/%llu\n",
263 (unsigned long long)sector, (unsigned long long)blockcount);
265 Reminder: sizeof() result is of type size_t.
267 Thank you for your cooperation and attention.
270 By Randy Dunlap <rdunlap@infradead.org> and
271 Andrew Murray <amurray@mpc-data.co.uk>