1If 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 12Raw 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 20 %pSR versatile_init+0x9/0x110 21 (with __builtin_extract_return_addr() translation) 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 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 58Physical addresses types phys_addr_t: 59 60 %pa[p] 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 66DMA 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 73Raw 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 105Raw 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 115MAC/FDDI addresses: 116 117 %pM 00:01:02:03:04:05 118 %pMR 05:04:03:02:01:00 119 %pMF 00-01-02-03-04-05 120 %pm 000102030405 121 %pmR 050403020100 122 123 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. 130 131 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 135IPv4 addresses: 136 137 %pI4 1.2.3.4 138 %pi4 001.002.003.004 139 %p[Ii]4[hnbl] 140 141 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 163IPv4/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 195UUID/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 210dentry 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 219struct 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. 233 234u64 SHOULD be printed with %llu/%llx: 235 236 printk("%llu", u64_var); 237 238s64 SHOULD be printed with %lld/%llx: 239 240 printk("%lld", s64_var); 241 242If <type> is dependent on a config option for its size (e.g., sector_t, 243blkcnt_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: 246 247 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 255By Randy Dunlap <rdunlap@infradead.org> and 256Andrew Murray <amurray@mpc-data.co.uk> 257