FreeBSD/Linux Kernel Cross Reference
sys/Documentation/printk-formats.txt

     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.
    
    Raw buffer as a hex string:
            %*ph    00 01 02  ...  3f
            %*phC   00:01:02: ... :3f
            %*phD   00-01-02- ... -3f
            %*phN   000102 ... 3f
    
            For printing a small buffers (up to 64 bytes long) as a hex string with
            certain separator. For the larger buffers consider to use
            print_hex_dump().
    
    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
            %pmR    050403020100
    
            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, phys_addr_t, resource_size_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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