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authorAndrew Murray <amurray@mpc-data.co.uk>2011-06-15 15:57:09 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2011-06-16 00:52:50 -0400
commit04c55715cbd5de526046745bca3d3b6ffa6641c6 (patch)
treefe63e426a56f951b8bb864ca850ceca61165d793 /Documentation/printk-formats.txt
parenta1b6ae8ed01736dae19a33e74ea4e8dd88f891b5 (diff)
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>
Diffstat (limited to 'Documentation/printk-formats.txt')
-rw-r--r--Documentation/printk-formats.txt119
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:
9 size_t %zu or %zx 9 size_t %zu or %zx
10 ssize_t %zd or %zx 10 ssize_t %zd or %zx
11 11
12Raw pointer value SHOULD be printed with %p. 12Raw pointer value SHOULD be printed with %p. The kernel supports
13the following extended format specifiers for pointer types:
14
15Symbols/Function Pointers:
16
17 %pF versatile_init+0x0/0x110
18 %pf versatile_init
19 %pS versatile_init+0x0/0x110
20 %ps versatile_init
21 %pB prev_fn_of_versatile_init+0x88/0x88
22
23 For printing symbols and function pointers. The 'S' and 's' specifiers
24 result in the symbol name with ('S') or without ('s') offsets. Where
25 this is used on a kernel without KALLSYMS - the symbol address is
26 printed instead.
27
28 The 'B' specifier results in the symbol name with offsets and should be
29 used when printing stack backtraces. The specifier takes into
30 consideration the effect of compiler optimisations which may occur
31 when tail-call's are used and marked with the noreturn GCC attribute.
32
33 On ia64, ppc64 and parisc64 architectures function pointers are
34 actually function descriptors which must first be resolved. The 'F' and
35 'f' specifiers perform this resolution and then provide the same
36 functionality as the 'S' and 's' specifiers.
37
38Kernel Pointers:
39
40 %pK 0x01234567 or 0x0123456789abcdef
41
42 For printing kernel pointers which should be hidden from unprivileged
43 users. The behaviour of %pK depends on the kptr_restrict sysctl - see
44 Documentation/sysctl/kernel.txt for more details.
45
46Struct Resources:
47
48 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
49 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
50 %pR [mem 0x60000000-0x6fffffff pref] or
51 [mem 0x0000000060000000-0x000000006fffffff pref]
52
53 For printing struct resources. The 'R' and 'r' specifiers result in a
54 printed resource with ('R') or without ('r') a decoded flags member.
55
56MAC/FDDI addresses:
57
58 %pM 00:01:02:03:04:05
59 %pMF 00-01-02-03-04-05
60 %pm 000102030405
61
62 For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
63 specifiers result in a printed address with ('M') or without ('m') byte
64 separators. The default byte separator is the colon (':').
65
66 Where FDDI addresses are concerned the 'F' specifier can be used after
67 the 'M' specifier to use dash ('-') separators instead of the default
68 separator.
69
70IPv4 addresses:
71
72 %pI4 1.2.3.4
73 %pi4 001.002.003.004
74 %p[Ii][hnbl]
75
76 For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
77 specifiers result in a printed address with ('i4') or without ('I4')
78 leading zeros.
79
80 The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
81 host, network, big or little endian order addresses respectively. Where
82 no specifier is provided the default network/big endian order is used.
83
84IPv6 addresses:
85
86 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
87 %pi6 00010002000300040005000600070008
88 %pI6c 1:2:3:4:5:6:7:8
89
90 For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
91 specifiers result in a printed address with ('I6') or without ('i6')
92 colon-separators. Leading zeros are always used.
93
94 The additional 'c' specifier can be used with the 'I' specifier to
95 print a compressed IPv6 address as described by
96 http://tools.ietf.org/html/rfc5952
97
98UUID/GUID addresses:
99
100 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
101 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
102 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
103 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
104
105 For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
106 'b' and 'B' specifiers are used to specify a little endian order in
107 lower ('l') or upper case ('L') hex characters - and big endian order
108 in lower ('b') or upper case ('B') hex characters.
109
110 Where no additional specifiers are used the default little endian
111 order with lower case hex characters will be printed.
112
113struct va_format:
114
115 %pV
116
117 For printing struct va_format structures. These contain a format string
118 and va_list as follows:
119
120 struct va_format {
121 const char *fmt;
122 va_list *va;
123 };
124
125 Do not use this feature without some mechanism to verify the
126 correctness of the format string and va_list arguments.
13 127
14u64 SHOULD be printed with %llu/%llx, (unsigned long long): 128u64 SHOULD be printed with %llu/%llx, (unsigned long long):
15 129
@@ -32,4 +146,5 @@ Reminder: sizeof() result is of type size_t.
32Thank you for your cooperation and attention. 146Thank you for your cooperation and attention.
33 147
34 148
35By Randy Dunlap <rdunlap@xenotime.net> 149By Randy Dunlap <rdunlap@xenotime.net> and
150Andrew Murray <amurray@mpc-data.co.uk>