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 s32 %d or %x 12 u32 %u or %x 13 s64 %lld or %llx 14 u64 %llu or %llx 15 16If <type> is dependent on a config option for its size (e.g., sector_t, 17blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a 18format specifier of its largest possible type and explicitly cast to it. 19Example: 20 21 printk("test: sector number/total blocks: %llu/%llu\n", 22 (unsigned long long)sector, (unsigned long long)blockcount); 23 24Reminder: sizeof() result is of type size_t. 25 26The kernel's printf does not support %n. For obvious reasons, floating 27point formats (%e, %f, %g, %a) are also not recognized. Use of any 28unsupported specifier or length qualifier results in a WARN and early 29return from vsnprintf. 30 31Raw pointer value SHOULD be printed with %p. The kernel supports 32the following extended format specifiers for pointer types: 33 34Symbols/Function Pointers: 35 36 %pF versatile_init+0x0/0x110 37 %pf versatile_init 38 %pS versatile_init+0x0/0x110 39 %pSR versatile_init+0x9/0x110 40 (with __builtin_extract_return_addr() translation) 41 %ps versatile_init 42 %pB prev_fn_of_versatile_init+0x88/0x88 43 44 For printing symbols and function pointers. The 'S' and 's' specifiers 45 result in the symbol name with ('S') or without ('s') offsets. Where 46 this is used on a kernel without KALLSYMS - the symbol address is 47 printed instead. 48 49 The 'B' specifier results in the symbol name with offsets and should be 50 used when printing stack backtraces. The specifier takes into 51 consideration the effect of compiler optimisations which may occur 52 when tail-call's are used and marked with the noreturn GCC attribute. 53 54 On ia64, ppc64 and parisc64 architectures function pointers are 55 actually function descriptors which must first be resolved. The 'F' and 56 'f' specifiers perform this resolution and then provide the same 57 functionality as the 'S' and 's' specifiers. 58 59Kernel Pointers: 60 61 %pK 0x01234567 or 0x0123456789abcdef 62 63 For printing kernel pointers which should be hidden from unprivileged 64 users. The behaviour of %pK depends on the kptr_restrict sysctl - see 65 Documentation/sysctl/kernel.txt for more details. 66 67Struct Resources: 68 69 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or 70 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200] 71 %pR [mem 0x60000000-0x6fffffff pref] or 72 [mem 0x0000000060000000-0x000000006fffffff pref] 73 74 For printing struct resources. The 'R' and 'r' specifiers result in a 75 printed resource with ('R') or without ('r') a decoded flags member. 76 Passed by reference. 77 78Physical addresses types phys_addr_t: 79 80 %pa[p] 0x01234567 or 0x0123456789abcdef 81 82 For printing a phys_addr_t type (and its derivatives, such as 83 resource_size_t) which can vary based on build options, regardless of 84 the width of the CPU data path. Passed by reference. 85 86DMA addresses types dma_addr_t: 87 88 %pad 0x01234567 or 0x0123456789abcdef 89 90 For printing a dma_addr_t type which can vary based on build options, 91 regardless of the width of the CPU data path. Passed by reference. 92 93Raw buffer as an escaped string: 94 95 %*pE[achnops] 96 97 For printing raw buffer as an escaped string. For the following buffer 98 99 1b 62 20 5c 43 07 22 90 0d 5d 100 101 few examples show how the conversion would be done (the result string 102 without surrounding quotes): 103 104 %*pE "\eb \C\a"\220\r]" 105 %*pEhp "\x1bb \C\x07"\x90\x0d]" 106 %*pEa "\e\142\040\\\103\a\042\220\r\135" 107 108 The conversion rules are applied according to an optional combination 109 of flags (see string_escape_mem() kernel documentation for the 110 details): 111 a - ESCAPE_ANY 112 c - ESCAPE_SPECIAL 113 h - ESCAPE_HEX 114 n - ESCAPE_NULL 115 o - ESCAPE_OCTAL 116 p - ESCAPE_NP 117 s - ESCAPE_SPACE 118 By default ESCAPE_ANY_NP is used. 119 120 ESCAPE_ANY_NP is the sane choice for many cases, in particularly for 121 printing SSIDs. 122 123 If field width is omitted the 1 byte only will be escaped. 124 125Raw buffer as a hex string: 126 127 %*ph 00 01 02 ... 3f 128 %*phC 00:01:02: ... :3f 129 %*phD 00-01-02- ... -3f 130 %*phN 000102 ... 3f 131 132 For printing a small buffers (up to 64 bytes long) as a hex string with 133 certain separator. For the larger buffers consider to use 134 print_hex_dump(). 135 136MAC/FDDI addresses: 137 138 %pM 00:01:02:03:04:05 139 %pMR 05:04:03:02:01:00 140 %pMF 00-01-02-03-04-05 141 %pm 000102030405 142 %pmR 050403020100 143 144 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm' 145 specifiers result in a printed address with ('M') or without ('m') byte 146 separators. The default byte separator is the colon (':'). 147 148 Where FDDI addresses are concerned the 'F' specifier can be used after 149 the 'M' specifier to use dash ('-') separators instead of the default 150 separator. 151 152 For Bluetooth addresses the 'R' specifier shall be used after the 'M' 153 specifier to use reversed byte order suitable for visual interpretation 154 of Bluetooth addresses which are in the little endian order. 155 156 Passed by reference. 157 158IPv4 addresses: 159 160 %pI4 1.2.3.4 161 %pi4 001.002.003.004 162 %p[Ii]4[hnbl] 163 164 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4' 165 specifiers result in a printed address with ('i4') or without ('I4') 166 leading zeros. 167 168 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify 169 host, network, big or little endian order addresses respectively. Where 170 no specifier is provided the default network/big endian order is used. 171 172 Passed by reference. 173 174IPv6 addresses: 175 176 %pI6 0001:0002:0003:0004:0005:0006:0007:0008 177 %pi6 00010002000300040005000600070008 178 %pI6c 1:2:3:4:5:6:7:8 179 180 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6' 181 specifiers result in a printed address with ('I6') or without ('i6') 182 colon-separators. Leading zeros are always used. 183 184 The additional 'c' specifier can be used with the 'I' specifier to 185 print a compressed IPv6 address as described by 186 http://tools.ietf.org/html/rfc5952 187 188 Passed by reference. 189 190IPv4/IPv6 addresses (generic, with port, flowinfo, scope): 191 192 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008 193 %piS 001.002.003.004 or 00010002000300040005000600070008 194 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8 195 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345 196 %p[Ii]S[pfschnbl] 197 198 For printing an IP address without the need to distinguish whether it's 199 of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr', 200 specified through 'IS' or 'iS', can be passed to this format specifier. 201 202 The additional 'p', 'f', and 's' specifiers are used to specify port 203 (IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix, 204 flowinfo a '/' and scope a '%', each followed by the actual value. 205 206 In case of an IPv6 address the compressed IPv6 address as described by 207 http://tools.ietf.org/html/rfc5952 is being used if the additional 208 specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in 209 case of additional specifiers 'p', 'f' or 's' as suggested by 210 https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07 211 212 In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l' 213 specifiers can be used as well and are ignored in case of an IPv6 214 address. 215 216 Passed by reference. 217 218 Further examples: 219 220 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789 221 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890 222 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789 223 224UUID/GUID addresses: 225 226 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f 227 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F 228 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f 229 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F 230 231 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L', 232 'b' and 'B' specifiers are used to specify a little endian order in 233 lower ('l') or upper case ('L') hex characters - and big endian order 234 in lower ('b') or upper case ('B') hex characters. 235 236 Where no additional specifiers are used the default big endian 237 order with lower case hex characters will be printed. 238 239 Passed by reference. 240 241dentry names: 242 243 %pd{,2,3,4} 244 %pD{,2,3,4} 245 246 For printing dentry name; if we race with d_move(), the name might be 247 a mix of old and new ones, but it won't oops. %pd dentry is a safer 248 equivalent of %s dentry->d_name.name we used to use, %pd<n> prints 249 n last components. %pD does the same thing for struct file. 250 251 Passed by reference. 252 253block_device names: 254 255 %pg sda, sda1 or loop0p1 256 257 For printing name of block_device pointers. 258 259struct va_format: 260 261 %pV 262 263 For printing struct va_format structures. These contain a format string 264 and va_list as follows: 265 266 struct va_format { 267 const char *fmt; 268 va_list *va; 269 }; 270 271 Implements a "recursive vsnprintf". 272 273 Do not use this feature without some mechanism to verify the 274 correctness of the format string and va_list arguments. 275 276 Passed by reference. 277 278struct clk: 279 280 %pC pll1 281 %pCn pll1 282 %pCr 1560000000 283 284 For printing struct clk structures. '%pC' and '%pCn' print the name 285 (Common Clock Framework) or address (legacy clock framework) of the 286 structure; '%pCr' prints the current clock rate. 287 288 Passed by reference. 289 290bitmap and its derivatives such as cpumask and nodemask: 291 292 %*pb 0779 293 %*pbl 0,3-6,8-10 294 295 For printing bitmap and its derivatives such as cpumask and nodemask, 296 %*pb output the bitmap with field width as the number of bits and %*pbl 297 output the bitmap as range list with field width as the number of bits. 298 299 Passed by reference. 300 301Flags bitfields such as page flags, gfp_flags: 302 303 %pGp referenced|uptodate|lru|active|private 304 %pGg GFP_USER|GFP_DMA32|GFP_NOWARN 305 %pGv read|exec|mayread|maywrite|mayexec|denywrite 306 307 For printing flags bitfields as a collection of symbolic constants that 308 would construct the value. The type of flags is given by the third 309 character. Currently supported are [p]age flags, [v]ma_flags (both 310 expect unsigned long *) and [g]fp_flags (expects gfp_t *). The flag 311 names and print order depends on the particular type. 312 313 Note that this format should not be used directly in TP_printk() part 314 of a tracepoint. Instead, use the show_*_flags() functions from 315 <trace/events/mmflags.h>. 316 317 Passed by reference. 318 319Network device features: 320 321 %pNF 0x000000000000c000 322 323 For printing netdev_features_t. 324 325 Passed by reference. 326 327If you add other %p extensions, please extend lib/test_printf.c with 328one or more test cases, if at all feasible. 329 330 331Thank you for your cooperation and attention. 332 333 334By Randy Dunlap <rdunlap@infradead.org> and 335Andrew Murray <amurray@mpc-data.co.uk> 336