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Documentation: update printk-formats.txt
This patch updates the incomplete documentation concerning the printk
extended format specifiers.
Signed-off-by: Andrew Murray <amurray@mpc-data.co.uk>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
authored by
Andrew Murray
and committed by
Linus Torvalds
04c55715
a1b6ae8e
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+117
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Documentation/printk-formats.txt
+117
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Documentation/printk-formats.txt
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size_t %zu or %zx
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ssize_t %zd or %zx
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Raw pointer value SHOULD be printed with %p.
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Raw pointer value SHOULD be printed with %p. The kernel supports
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the following extended format specifiers for pointer types:
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Symbols/Function Pointers:
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%pF versatile_init+0x0/0x110
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%pf versatile_init
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%pS versatile_init+0x0/0x110
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%ps versatile_init
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%pB prev_fn_of_versatile_init+0x88/0x88
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For printing symbols and function pointers. The 'S' and 's' specifiers
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result in the symbol name with ('S') or without ('s') offsets. Where
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this is used on a kernel without KALLSYMS - the symbol address is
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printed instead.
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The 'B' specifier results in the symbol name with offsets and should be
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used when printing stack backtraces. The specifier takes into
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consideration the effect of compiler optimisations which may occur
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when tail-call's are used and marked with the noreturn GCC attribute.
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On ia64, ppc64 and parisc64 architectures function pointers are
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actually function descriptors which must first be resolved. The 'F' and
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'f' specifiers perform this resolution and then provide the same
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functionality as the 'S' and 's' specifiers.
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Kernel Pointers:
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%pK 0x01234567 or 0x0123456789abcdef
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For printing kernel pointers which should be hidden from unprivileged
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users. The behaviour of %pK depends on the kptr_restrict sysctl - see
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Documentation/sysctl/kernel.txt for more details.
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Struct Resources:
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%pr [mem 0x60000000-0x6fffffff flags 0x2200] or
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[mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
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%pR [mem 0x60000000-0x6fffffff pref] or
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[mem 0x0000000060000000-0x000000006fffffff pref]
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For printing struct resources. The 'R' and 'r' specifiers result in a
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printed resource with ('R') or without ('r') a decoded flags member.
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MAC/FDDI addresses:
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%pM 00:01:02:03:04:05
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%pMF 00-01-02-03-04-05
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%pm 000102030405
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For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
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specifiers result in a printed address with ('M') or without ('m') byte
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separators. The default byte separator is the colon (':').
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Where FDDI addresses are concerned the 'F' specifier can be used after
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the 'M' specifier to use dash ('-') separators instead of the default
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separator.
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IPv4 addresses:
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%pI4 1.2.3.4
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%pi4 001.002.003.004
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%p[Ii][hnbl]
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For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
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specifiers result in a printed address with ('i4') or without ('I4')
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leading zeros.
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The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
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host, network, big or little endian order addresses respectively. Where
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no specifier is provided the default network/big endian order is used.
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IPv6 addresses:
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%pI6 0001:0002:0003:0004:0005:0006:0007:0008
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%pi6 00010002000300040005000600070008
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%pI6c 1:2:3:4:5:6:7:8
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For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
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specifiers result in a printed address with ('I6') or without ('i6')
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colon-separators. Leading zeros are always used.
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The additional 'c' specifier can be used with the 'I' specifier to
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print a compressed IPv6 address as described by
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http://tools.ietf.org/html/rfc5952
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UUID/GUID addresses:
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%pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
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%pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
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%pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
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%pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
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For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
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'b' and 'B' specifiers are used to specify a little endian order in
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lower ('l') or upper case ('L') hex characters - and big endian order
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in lower ('b') or upper case ('B') hex characters.
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Where no additional specifiers are used the default little endian
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order with lower case hex characters will be printed.
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struct va_format:
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%pV
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For printing struct va_format structures. These contain a format string
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and va_list as follows:
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struct va_format {
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const char *fmt;
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va_list *va;
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};
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Do not use this feature without some mechanism to verify the
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correctness of the format string and va_list arguments.
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u64 SHOULD be printed with %llu/%llx, (unsigned long long):
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···
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Thank you for your cooperation and attention.
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By Randy Dunlap <rdunlap@xenotime.net>
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By Randy Dunlap <rdunlap@xenotime.net> and
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Andrew Murray <amurray@mpc-data.co.uk>