diff options
Diffstat (limited to 'Documentation/printk-formats.txt')
| -rw-r--r-- | Documentation/printk-formats.txt | 119 |
1 files changed, 117 insertions, 2 deletions
diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt index 1b5a5ddbc3e..5df176ed59b 100644 --- a/Documentation/printk-formats.txt +++ b/Documentation/printk-formats.txt @@ -9,7 +9,121 @@ If variable is of Type, use printk format specifier: size_t %zu or %zx ssize_t %zd or %zx -Raw pointer value SHOULD be printed with %p. +Raw pointer value SHOULD be printed with %p. The kernel supports +the following extended format specifiers for pointer types: + +Symbols/Function Pointers: + + %pF versatile_init+0x0/0x110 + %pf versatile_init + %pS versatile_init+0x0/0x110 + %ps versatile_init + %pB prev_fn_of_versatile_init+0x88/0x88 + + For printing symbols and function pointers. The 'S' and 's' specifiers + result in the symbol name with ('S') or without ('s') offsets. Where + this is used on a kernel without KALLSYMS - the symbol address is + printed instead. + + The 'B' specifier results in the symbol name with offsets and should be + used when printing stack backtraces. The specifier takes into + consideration the effect of compiler optimisations which may occur + when tail-call's are used and marked with the noreturn GCC attribute. + + On ia64, ppc64 and parisc64 architectures function pointers are + actually function descriptors which must first be resolved. The 'F' and + 'f' specifiers perform this resolution and then provide the same + functionality as the 'S' and 's' specifiers. + +Kernel Pointers: + + %pK 0x01234567 or 0x0123456789abcdef + + For printing kernel pointers which should be hidden from unprivileged + users. The behaviour of %pK depends on the kptr_restrict sysctl - see + Documentation/sysctl/kernel.txt for more details. + +Struct Resources: + + %pr [mem 0x60000000-0x6fffffff flags 0x2200] or + [mem 0x0000000060000000-0x000000006fffffff flags 0x2200] + %pR [mem 0x60000000-0x6fffffff pref] or + [mem 0x0000000060000000-0x000000006fffffff pref] + + For printing struct resources. The 'R' and 'r' specifiers result in a + printed resource with ('R') or without ('r') a decoded flags member. + +MAC/FDDI addresses: + + %pM 00:01:02:03:04:05 + %pMF 00-01-02-03-04-05 + %pm 000102030405 + + For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm' + specifiers result in a printed address with ('M') or without ('m') byte + separators. The default byte separator is the colon (':'). + + Where FDDI addresses are concerned the 'F' specifier can be used after + the 'M' specifier to use dash ('-') separators instead of the default + separator. + +IPv4 addresses: + + %pI4 1.2.3.4 + %pi4 001.002.003.004 + %p[Ii][hnbl] + + For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4' + specifiers result in a printed address with ('i4') or without ('I4') + leading zeros. + + The additional 'h', 'n', 'b', and 'l' specifiers are used to specify + host, network, big or little endian order addresses respectively. Where + no specifier is provided the default network/big endian order is used. + +IPv6 addresses: + + %pI6 0001:0002:0003:0004:0005:0006:0007:0008 + %pi6 00010002000300040005000600070008 + %pI6c 1:2:3:4:5:6:7:8 + + For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6' + specifiers result in a printed address with ('I6') or without ('i6') + colon-separators. Leading zeros are always used. + + The additional 'c' specifier can be used with the 'I' specifier to + print a compressed IPv6 address as described by + http://tools.ietf.org/html/rfc5952 + +UUID/GUID addresses: + + %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f + %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F + %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f + %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F + + For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L', + 'b' and 'B' specifiers are used to specify a little endian order in + lower ('l') or upper case ('L') hex characters - and big endian order + in lower ('b') or upper case ('B') hex characters. + + Where no additional specifiers are used the default little endian + order with lower case hex characters will be printed. + +struct va_format: + + %pV + + For printing struct va_format structures. These contain a format string + and va_list as follows: + + struct va_format { + const char *fmt; + va_list *va; + }; + + Do not use this feature without some mechanism to verify the + correctness of the format string and va_list arguments. u64 SHOULD be printed with %llu/%llx, (unsigned long long): @@ -32,4 +146,5 @@ Reminder: sizeof() result is of type size_t. Thank you for your cooperation and attention. -By Randy Dunlap <rdunlap@xenotime.net> +By Randy Dunlap <rdunlap@xenotime.net> and +Andrew Murray <amurray@mpc-data.co.uk> |