About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / printk-formats.txt




Custom Search

Based on kernel version 4.1. Page generated on 2015-06-28 12:14 EST.

1	If variable is of Type,		use printk format specifier:
2	---------------------------------------------------------
3			int			%d or %x
4			unsigned int		%u or %x
5			long			%ld or %lx
6			unsigned long		%lu or %lx
7			long long		%lld or %llx
8			unsigned long long	%llu or %llx
9			size_t			%zu or %zx
10			ssize_t			%zd or %zx
11			s32			%d or %x
12			u32			%u or %x
13			s64			%lld or %llx
14			u64			%llu or %llx
15	
16	If <type> is dependent on a config option for its size (e.g., sector_t,
17	blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
18	format specifier of its largest possible type and explicitly cast to it.
19	Example:
20	
21		printk("test: sector number/total blocks: %llu/%llu\n",
22			(unsigned long long)sector, (unsigned long long)blockcount);
23	
24	Reminder: sizeof() result is of type size_t.
25	
26	
27	Raw pointer value SHOULD be printed with %p. The kernel supports
28	the following extended format specifiers for pointer types:
29	
30	Symbols/Function Pointers:
31	
32		%pF	versatile_init+0x0/0x110
33		%pf	versatile_init
34		%pS	versatile_init+0x0/0x110
35		%pSR	versatile_init+0x9/0x110
36			(with __builtin_extract_return_addr() translation)
37		%ps	versatile_init
38		%pB	prev_fn_of_versatile_init+0x88/0x88
39	
40		For printing symbols and function pointers. The 'S' and 's' specifiers
41		result in the symbol name with ('S') or without ('s') offsets. Where
42		this is used on a kernel without KALLSYMS - the symbol address is
43		printed instead.
44	
45		The 'B' specifier results in the symbol name with offsets and should be
46		used when printing stack backtraces. The specifier takes into
47		consideration the effect of compiler optimisations which may occur
48		when tail-call's are used and marked with the noreturn GCC attribute.
49	
50		On ia64, ppc64 and parisc64 architectures function pointers are
51		actually function descriptors which must first be resolved. The 'F' and
52		'f' specifiers perform this resolution and then provide the same
53		functionality as the 'S' and 's' specifiers.
54	
55	Kernel Pointers:
56	
57		%pK	0x01234567 or 0x0123456789abcdef
58	
59		For printing kernel pointers which should be hidden from unprivileged
60		users. The behaviour of %pK depends on the kptr_restrict sysctl - see
61		Documentation/sysctl/kernel.txt for more details.
62	
63	Struct Resources:
64	
65		%pr	[mem 0x60000000-0x6fffffff flags 0x2200] or
66			[mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
67		%pR	[mem 0x60000000-0x6fffffff pref] or
68			[mem 0x0000000060000000-0x000000006fffffff pref]
69	
70		For printing struct resources. The 'R' and 'r' specifiers result in a
71		printed resource with ('R') or without ('r') a decoded flags member.
72		Passed by reference.
73	
74	Physical addresses types phys_addr_t:
75	
76		%pa[p]	0x01234567 or 0x0123456789abcdef
77	
78		For printing a phys_addr_t type (and its derivatives, such as
79		resource_size_t) which can vary based on build options, regardless of
80		the width of the CPU data path. Passed by reference.
81	
82	DMA addresses types dma_addr_t:
83	
84		%pad	0x01234567 or 0x0123456789abcdef
85	
86		For printing a dma_addr_t type which can vary based on build options,
87		regardless of the width of the CPU data path. Passed by reference.
88	
89	Raw buffer as an escaped string:
90	
91		%*pE[achnops]
92	
93		For printing raw buffer as an escaped string. For the following buffer
94	
95			1b 62 20 5c 43 07 22 90 0d 5d
96	
97		few examples show how the conversion would be done (the result string
98		without surrounding quotes):
99	
100			%*pE		"\eb \C\a"\220\r]"
101			%*pEhp		"\x1bb \C\x07"\x90\x0d]"
102			%*pEa		"\e\142\040\\\103\a\042\220\r\135"
103	
104		The conversion rules are applied according to an optional combination
105		of flags (see string_escape_mem() kernel documentation for the
106		details):
107			a - ESCAPE_ANY
108			c - ESCAPE_SPECIAL
109			h - ESCAPE_HEX
110			n - ESCAPE_NULL
111			o - ESCAPE_OCTAL
112			p - ESCAPE_NP
113			s - ESCAPE_SPACE
114		By default ESCAPE_ANY_NP is used.
115	
116		ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
117		printing SSIDs.
118	
119		If field width is omitted the 1 byte only will be escaped.
120	
121	Raw buffer as a hex string:
122		%*ph	00 01 02  ...  3f
123		%*phC	00:01:02: ... :3f
124		%*phD	00-01-02- ... -3f
125		%*phN	000102 ... 3f
126	
127		For printing a small buffers (up to 64 bytes long) as a hex string with
128		certain separator. For the larger buffers consider to use
129		print_hex_dump().
130	
131	MAC/FDDI addresses:
132	
133		%pM	00:01:02:03:04:05
134		%pMR	05:04:03:02:01:00
135		%pMF	00-01-02-03-04-05
136		%pm	000102030405
137		%pmR	050403020100
138	
139		For printing 6-byte MAC/FDDI addresses in hex notation. The 'M' and 'm'
140		specifiers result in a printed address with ('M') or without ('m') byte
141		separators. The default byte separator is the colon (':').
142	
143		Where FDDI addresses are concerned the 'F' specifier can be used after
144		the 'M' specifier to use dash ('-') separators instead of the default
145		separator.
146	
147		For Bluetooth addresses the 'R' specifier shall be used after the 'M'
148		specifier to use reversed byte order suitable for visual interpretation
149		of Bluetooth addresses which are in the little endian order.
150	
151		Passed by reference.
152	
153	IPv4 addresses:
154	
155		%pI4	1.2.3.4
156		%pi4	001.002.003.004
157		%p[Ii]4[hnbl]
158	
159		For printing IPv4 dot-separated decimal addresses. The 'I4' and 'i4'
160		specifiers result in a printed address with ('i4') or without ('I4')
161		leading zeros.
162	
163		The additional 'h', 'n', 'b', and 'l' specifiers are used to specify
164		host, network, big or little endian order addresses respectively. Where
165		no specifier is provided the default network/big endian order is used.
166	
167		Passed by reference.
168	
169	IPv6 addresses:
170	
171		%pI6	0001:0002:0003:0004:0005:0006:0007:0008
172		%pi6	00010002000300040005000600070008
173		%pI6c	1:2:3:4:5:6:7:8
174	
175		For printing IPv6 network-order 16-bit hex addresses. The 'I6' and 'i6'
176		specifiers result in a printed address with ('I6') or without ('i6')
177		colon-separators. Leading zeros are always used.
178	
179		The additional 'c' specifier can be used with the 'I' specifier to
180		print a compressed IPv6 address as described by
181		http://tools.ietf.org/html/rfc5952
182	
183		Passed by reference.
184	
185	IPv4/IPv6 addresses (generic, with port, flowinfo, scope):
186	
187		%pIS	1.2.3.4		or 0001:0002:0003:0004:0005:0006:0007:0008
188		%piS	001.002.003.004	or 00010002000300040005000600070008
189		%pISc	1.2.3.4		or 1:2:3:4:5:6:7:8
190		%pISpc	1.2.3.4:12345	or [1:2:3:4:5:6:7:8]:12345
191		%p[Ii]S[pfschnbl]
192	
193		For printing an IP address without the need to distinguish whether it's
194		of type AF_INET or AF_INET6, a pointer to a valid 'struct sockaddr',
195		specified through 'IS' or 'iS', can be passed to this format specifier.
196	
197		The additional 'p', 'f', and 's' specifiers are used to specify port
198		(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ':' prefix,
199		flowinfo a '/' and scope a '%', each followed by the actual value.
200	
201		In case of an IPv6 address the compressed IPv6 address as described by
202		http://tools.ietf.org/html/rfc5952 is being used if the additional
203		specifier 'c' is given. The IPv6 address is surrounded by '[', ']' in
204		case of additional specifiers 'p', 'f' or 's' as suggested by
205		https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
206	
207		In case of IPv4 addresses, the additional 'h', 'n', 'b', and 'l'
208		specifiers can be used as well and are ignored in case of an IPv6
209		address.
210	
211		Passed by reference.
212	
213		Further examples:
214	
215		%pISfc		1.2.3.4		or [1:2:3:4:5:6:7:8]/123456789
216		%pISsc		1.2.3.4		or [1:2:3:4:5:6:7:8]%1234567890
217		%pISpfc		1.2.3.4:12345	or [1:2:3:4:5:6:7:8]:12345/123456789
218	
219	UUID/GUID addresses:
220	
221		%pUb	00010203-0405-0607-0809-0a0b0c0d0e0f
222		%pUB	00010203-0405-0607-0809-0A0B0C0D0E0F
223		%pUl	03020100-0504-0706-0809-0a0b0c0e0e0f
224		%pUL	03020100-0504-0706-0809-0A0B0C0E0E0F
225	
226		For printing 16-byte UUID/GUIDs addresses. The additional 'l', 'L',
227		'b' and 'B' specifiers are used to specify a little endian order in
228		lower ('l') or upper case ('L') hex characters - and big endian order
229		in lower ('b') or upper case ('B') hex characters.
230	
231		Where no additional specifiers are used the default big endian
232		order with lower case hex characters will be printed.
233	
234		Passed by reference.
235	
236	dentry names:
237		%pd{,2,3,4}
238		%pD{,2,3,4}
239	
240		For printing dentry name; if we race with d_move(), the name might be
241		a mix of old and new ones, but it won't oops.  %pd dentry is a safer
242		equivalent of %s dentry->d_name.name we used to use, %pd<n> prints
243		n last components.  %pD does the same thing for struct file.
244	
245		Passed by reference.
246	
247	struct va_format:
248	
249		%pV
250	
251		For printing struct va_format structures. These contain a format string
252		and va_list as follows:
253	
254		struct va_format {
255			const char *fmt;
256			va_list *va;
257		};
258	
259		Do not use this feature without some mechanism to verify the
260		correctness of the format string and va_list arguments.
261	
262		Passed by reference.
263	
264	struct clk:
265	
266		%pC	pll1
267		%pCn	pll1
268		%pCr	1560000000
269	
270		For printing struct clk structures. '%pC' and '%pCn' print the name
271		(Common Clock Framework) or address (legacy clock framework) of the
272		structure; '%pCr' prints the current clock rate.
273	
274		Passed by reference.
275	
276	bitmap and its derivatives such as cpumask and nodemask:
277	
278		%*pb	0779
279		%*pbl	0,3-6,8-10
280	
281		For printing bitmap and its derivatives such as cpumask and nodemask,
282		%*pb output the bitmap with field width as the number of bits and %*pbl
283		output the bitmap as range list with field width as the number of bits.
284	
285		Passed by reference.
286	
287	Thank you for your cooperation and attention.
288	
289	
290	By Randy Dunlap <rdunlap@infradead.org> and
291	Andrew Murray <amurray@mpc-data.co.uk>
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.