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- If variable is of Type, use printk format specifier:
- ---------------------------------------------------------
- int %d or %x
- unsigned int %u or %x
- long %ld or %lx
- unsigned long %lu or %lx
- long long %lld or %llx
- unsigned long long %llu or %llx
- size_t %zu or %zx
- ssize_t %zd or %zx
- 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.
- Physical addresses:
- %pa 0x01234567 or 0x0123456789abcdef
- For printing a phys_addr_t type (and its derivatives, such as
- resource_size_t) which can vary based on build options, regardless of
- the width of the CPU data path. Passed by reference.
- MAC/FDDI addresses:
- %pM 00:01:02:03:04:05
- %pMR 05:04:03:02:01:00
- %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.
- For Bluetooth addresses the 'R' specifier shall be used after the 'M'
- specifier to use reversed byte order suitable for visual interpretation
- of Bluetooth addresses which are in the little endian order.
- 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):
- printk("%llu", (unsigned long long)u64_var);
- s64 SHOULD be printed with %lld/%llx, (long long):
- printk("%lld", (long long)s64_var);
- If <type> is dependent on a config option for its size (e.g., sector_t,
- blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
- format specifier of its largest possible type and explicitly cast to it.
- Example:
- printk("test: sector number/total blocks: %llu/%llu\n",
- (unsigned long long)sector, (unsigned long long)blockcount);
- Reminder: sizeof() result is of type size_t.
- Thank you for your cooperation and attention.
- By Randy Dunlap <rdunlap@xenotime.net> and
- Andrew Murray <amurray@mpc-data.co.uk>
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