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1=========================================
2How to get printk format specifiers right
3=========================================
4
5:Author: Randy Dunlap <rdunlap@infradead.org>
6:Author: Andrew Murray <amurray@mpc-data.co.uk>
7
8
9Integer types
10=============
11
12::
13
14 If variable is of Type, use printk format specifier:
15 ------------------------------------------------------------
16 char %d or %x
17 unsigned char %u or %x
18 short int %d or %x
19 unsigned short int %u or %x
20 int %d or %x
21 unsigned int %u or %x
22 long %ld or %lx
23 unsigned long %lu or %lx
24 long long %lld or %llx
25 unsigned long long %llu or %llx
26 size_t %zu or %zx
27 ssize_t %zd or %zx
28 s8 %d or %x
29 u8 %u or %x
30 s16 %d or %x
31 u16 %u or %x
32 s32 %d or %x
33 u32 %u or %x
34 s64 %lld or %llx
35 u64 %llu or %llx
36
37
38If <type> is dependent on a config option for its size (e.g., sector_t,
39blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
40format specifier of its largest possible type and explicitly cast to it.
41
42Example::
43
44 printk("test: sector number/total blocks: %llu/%llu\n",
45 (unsigned long long)sector, (unsigned long long)blockcount);
46
47Reminder: sizeof() returns type size_t.
48
49The kernel's printf does not support %n. Floating point formats (%e, %f,
50%g, %a) are also not recognized, for obvious reasons. Use of any
51unsupported specifier or length qualifier results in a WARN and early
52return from vsnprintf().
53
54Pointer types
55=============
56
57A raw pointer value may be printed with %p which will hash the address
58before printing. The kernel also supports extended specifiers for printing
59pointers of different types.
60
61Some of the extended specifiers print the data on the given address instead
62of printing the address itself. In this case, the following error messages
63might be printed instead of the unreachable information::
64
65 (null) data on plain NULL address
66 (efault) data on invalid address
67 (einval) invalid data on a valid address
68
69Plain Pointers
70--------------
71
72::
73
74 %p abcdef12 or 00000000abcdef12
75
76Pointers printed without a specifier extension (i.e unadorned %p) are
77hashed to prevent leaking information about the kernel memory layout. This
78has the added benefit of providing a unique identifier. On 64-bit machines
79the first 32 bits are zeroed. The kernel will print ``(ptrval)`` until it
80gathers enough entropy. If you *really* want the address see %px below.
81
82Symbols/Function Pointers
83-------------------------
84
85::
86
87 %pS versatile_init+0x0/0x110
88 %ps versatile_init
89 %pF versatile_init+0x0/0x110
90 %pf versatile_init
91 %pSR versatile_init+0x9/0x110
92 (with __builtin_extract_return_addr() translation)
93 %pB prev_fn_of_versatile_init+0x88/0x88
94
95
96The ``S`` and ``s`` specifiers are used for printing a pointer in symbolic
97format. They result in the symbol name with (S) or without (s)
98offsets. If KALLSYMS are disabled then the symbol address is printed instead.
99
100Note, that the ``F`` and ``f`` specifiers are identical to ``S`` (``s``)
101and thus deprecated. We have ``F`` and ``f`` because on ia64, ppc64 and
102parisc64 function pointers are indirect and, in fact, are function
103descriptors, which require additional dereferencing before we can lookup
104the symbol. As of now, ``S`` and ``s`` perform dereferencing on those
105platforms (when needed), so ``F`` and ``f`` exist for compatibility
106reasons only.
107
108The ``B`` specifier results in the symbol name with offsets and should be
109used when printing stack backtraces. The specifier takes into
110consideration the effect of compiler optimisations which may occur
111when tail-calls are used and marked with the noreturn GCC attribute.
112
113Kernel Pointers
114---------------
115
116::
117
118 %pK 01234567 or 0123456789abcdef
119
120For printing kernel pointers which should be hidden from unprivileged
121users. The behaviour of %pK depends on the kptr_restrict sysctl - see
122Documentation/admin-guide/sysctl/kernel.rst for more details.
123
124Unmodified Addresses
125--------------------
126
127::
128
129 %px 01234567 or 0123456789abcdef
130
131For printing pointers when you *really* want to print the address. Please
132consider whether or not you are leaking sensitive information about the
133kernel memory layout before printing pointers with %px. %px is functionally
134equivalent to %lx (or %lu). %px is preferred because it is more uniquely
135grep'able. If in the future we need to modify the way the kernel handles
136printing pointers we will be better equipped to find the call sites.
137
138Struct Resources
139----------------
140
141::
142
143 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
144 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
145 %pR [mem 0x60000000-0x6fffffff pref] or
146 [mem 0x0000000060000000-0x000000006fffffff pref]
147
148For printing struct resources. The ``R`` and ``r`` specifiers result in a
149printed resource with (R) or without (r) a decoded flags member.
150
151Passed by reference.
152
153Physical address types phys_addr_t
154----------------------------------
155
156::
157
158 %pa[p] 0x01234567 or 0x0123456789abcdef
159
160For printing a phys_addr_t type (and its derivatives, such as
161resource_size_t) which can vary based on build options, regardless of the
162width of the CPU data path.
163
164Passed by reference.
165
166DMA address types dma_addr_t
167----------------------------
168
169::
170
171 %pad 0x01234567 or 0x0123456789abcdef
172
173For printing a dma_addr_t type which can vary based on build options,
174regardless of the width of the CPU data path.
175
176Passed by reference.
177
178Raw buffer as an escaped string
179-------------------------------
180
181::
182
183 %*pE[achnops]
184
185For printing raw buffer as an escaped string. For the following buffer::
186
187 1b 62 20 5c 43 07 22 90 0d 5d
188
189A few examples show how the conversion would be done (excluding surrounding
190quotes)::
191
192 %*pE "\eb \C\a"\220\r]"
193 %*pEhp "\x1bb \C\x07"\x90\x0d]"
194 %*pEa "\e\142\040\\\103\a\042\220\r\135"
195
196The conversion rules are applied according to an optional combination
197of flags (see :c:func:`string_escape_mem` kernel documentation for the
198details):
199
200 - a - ESCAPE_ANY
201 - c - ESCAPE_SPECIAL
202 - h - ESCAPE_HEX
203 - n - ESCAPE_NULL
204 - o - ESCAPE_OCTAL
205 - p - ESCAPE_NP
206 - s - ESCAPE_SPACE
207
208By default ESCAPE_ANY_NP is used.
209
210ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
211printing SSIDs.
212
213If field width is omitted then 1 byte only will be escaped.
214
215Raw buffer as a hex string
216--------------------------
217
218::
219
220 %*ph 00 01 02 ... 3f
221 %*phC 00:01:02: ... :3f
222 %*phD 00-01-02- ... -3f
223 %*phN 000102 ... 3f
224
225For printing small buffers (up to 64 bytes long) as a hex string with a
226certain separator. For larger buffers consider using
227:c:func:`print_hex_dump`.
228
229MAC/FDDI addresses
230------------------
231
232::
233
234 %pM 00:01:02:03:04:05
235 %pMR 05:04:03:02:01:00
236 %pMF 00-01-02-03-04-05
237 %pm 000102030405
238 %pmR 050403020100
239
240For printing 6-byte MAC/FDDI addresses in hex notation. The ``M`` and ``m``
241specifiers result in a printed address with (M) or without (m) byte
242separators. The default byte separator is the colon (:).
243
244Where FDDI addresses are concerned the ``F`` specifier can be used after
245the ``M`` specifier to use dash (-) separators instead of the default
246separator.
247
248For Bluetooth addresses the ``R`` specifier shall be used after the ``M``
249specifier to use reversed byte order suitable for visual interpretation
250of Bluetooth addresses which are in the little endian order.
251
252Passed by reference.
253
254IPv4 addresses
255--------------
256
257::
258
259 %pI4 1.2.3.4
260 %pi4 001.002.003.004
261 %p[Ii]4[hnbl]
262
263For printing IPv4 dot-separated decimal addresses. The ``I4`` and ``i4``
264specifiers result in a printed address with (i4) or without (I4) leading
265zeros.
266
267The additional ``h``, ``n``, ``b``, and ``l`` specifiers are used to specify
268host, network, big or little endian order addresses respectively. Where
269no specifier is provided the default network/big endian order is used.
270
271Passed by reference.
272
273IPv6 addresses
274--------------
275
276::
277
278 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
279 %pi6 00010002000300040005000600070008
280 %pI6c 1:2:3:4:5:6:7:8
281
282For printing IPv6 network-order 16-bit hex addresses. The ``I6`` and ``i6``
283specifiers result in a printed address with (I6) or without (i6)
284colon-separators. Leading zeros are always used.
285
286The additional ``c`` specifier can be used with the ``I`` specifier to
287print a compressed IPv6 address as described by
288http://tools.ietf.org/html/rfc5952
289
290Passed by reference.
291
292IPv4/IPv6 addresses (generic, with port, flowinfo, scope)
293---------------------------------------------------------
294
295::
296
297 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
298 %piS 001.002.003.004 or 00010002000300040005000600070008
299 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
300 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
301 %p[Ii]S[pfschnbl]
302
303For printing an IP address without the need to distinguish whether it's of
304type AF_INET or AF_INET6. A pointer to a valid struct sockaddr,
305specified through ``IS`` or ``iS``, can be passed to this format specifier.
306
307The additional ``p``, ``f``, and ``s`` specifiers are used to specify port
308(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ``:`` prefix,
309flowinfo a ``/`` and scope a ``%``, each followed by the actual value.
310
311In case of an IPv6 address the compressed IPv6 address as described by
312http://tools.ietf.org/html/rfc5952 is being used if the additional
313specifier ``c`` is given. The IPv6 address is surrounded by ``[``, ``]`` in
314case of additional specifiers ``p``, ``f`` or ``s`` as suggested by
315https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
316
317In case of IPv4 addresses, the additional ``h``, ``n``, ``b``, and ``l``
318specifiers can be used as well and are ignored in case of an IPv6
319address.
320
321Passed by reference.
322
323Further examples::
324
325 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
326 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
327 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
328
329UUID/GUID addresses
330-------------------
331
332::
333
334 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
335 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
336 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
337 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
338
339For printing 16-byte UUID/GUIDs addresses. The additional ``l``, ``L``,
340``b`` and ``B`` specifiers are used to specify a little endian order in
341lower (l) or upper case (L) hex notation - and big endian order in lower (b)
342or upper case (B) hex notation.
343
344Where no additional specifiers are used the default big endian
345order with lower case hex notation will be printed.
346
347Passed by reference.
348
349dentry names
350------------
351
352::
353
354 %pd{,2,3,4}
355 %pD{,2,3,4}
356
357For printing dentry name; if we race with :c:func:`d_move`, the name might
358be a mix of old and new ones, but it won't oops. %pd dentry is a safer
359equivalent of %s dentry->d_name.name we used to use, %pd<n> prints ``n``
360last components. %pD does the same thing for struct file.
361
362Passed by reference.
363
364block_device names
365------------------
366
367::
368
369 %pg sda, sda1 or loop0p1
370
371For printing name of block_device pointers.
372
373struct va_format
374----------------
375
376::
377
378 %pV
379
380For printing struct va_format structures. These contain a format string
381and va_list as follows::
382
383 struct va_format {
384 const char *fmt;
385 va_list *va;
386 };
387
388Implements a "recursive vsnprintf".
389
390Do not use this feature without some mechanism to verify the
391correctness of the format string and va_list arguments.
392
393Passed by reference.
394
395Device tree nodes
396-----------------
397
398::
399
400 %pOF[fnpPcCF]
401
402
403For printing device tree node structures. Default behaviour is
404equivalent to %pOFf.
405
406 - f - device node full_name
407 - n - device node name
408 - p - device node phandle
409 - P - device node path spec (name + @unit)
410 - F - device node flags
411 - c - major compatible string
412 - C - full compatible string
413
414The separator when using multiple arguments is ':'
415
416Examples::
417
418 %pOF /foo/bar@0 - Node full name
419 %pOFf /foo/bar@0 - Same as above
420 %pOFfp /foo/bar@0:10 - Node full name + phandle
421 %pOFfcF /foo/bar@0:foo,device:--P- - Node full name +
422 major compatible string +
423 node flags
424 D - dynamic
425 d - detached
426 P - Populated
427 B - Populated bus
428
429Passed by reference.
430
431Time and date (struct rtc_time)
432-------------------------------
433
434::
435
436 %ptR YYYY-mm-ddTHH:MM:SS
437 %ptRd YYYY-mm-dd
438 %ptRt HH:MM:SS
439 %ptR[dt][r]
440
441For printing date and time as represented by struct rtc_time structure in
442human readable format.
443
444By default year will be incremented by 1900 and month by 1. Use %ptRr (raw)
445to suppress this behaviour.
446
447Passed by reference.
448
449struct clk
450----------
451
452::
453
454 %pC pll1
455 %pCn pll1
456
457For printing struct clk structures. %pC and %pCn print the name of the clock
458(Common Clock Framework) or a unique 32-bit ID (legacy clock framework).
459
460Passed by reference.
461
462bitmap and its derivatives such as cpumask and nodemask
463-------------------------------------------------------
464
465::
466
467 %*pb 0779
468 %*pbl 0,3-6,8-10
469
470For printing bitmap and its derivatives such as cpumask and nodemask,
471%*pb outputs the bitmap with field width as the number of bits and %*pbl
472output the bitmap as range list with field width as the number of bits.
473
474Passed by reference.
475
476Flags bitfields such as page flags, gfp_flags
477---------------------------------------------
478
479::
480
481 %pGp referenced|uptodate|lru|active|private
482 %pGg GFP_USER|GFP_DMA32|GFP_NOWARN
483 %pGv read|exec|mayread|maywrite|mayexec|denywrite
484
485For printing flags bitfields as a collection of symbolic constants that
486would construct the value. The type of flags is given by the third
487character. Currently supported are [p]age flags, [v]ma_flags (both
488expect ``unsigned long *``) and [g]fp_flags (expects ``gfp_t *``). The flag
489names and print order depends on the particular type.
490
491Note that this format should not be used directly in the
492:c:func:`TP_printk()` part of a tracepoint. Instead, use the show_*_flags()
493functions from <trace/events/mmflags.h>.
494
495Passed by reference.
496
497Network device features
498-----------------------
499
500::
501
502 %pNF 0x000000000000c000
503
504For printing netdev_features_t.
505
506Passed by reference.
507
508Thanks
509======
510
511If you add other %p extensions, please extend <lib/test_printf.c> with
512one or more test cases, if at all feasible.
513
514Thank you for your cooperation and attention.
1=========================================
2How to get printk format specifiers right
3=========================================
4
5:Author: Randy Dunlap <rdunlap@infradead.org>
6:Author: Andrew Murray <amurray@mpc-data.co.uk>
7
8
9Integer types
10=============
11
12::
13
14 If variable is of Type, use printk format specifier:
15 ------------------------------------------------------------
16 int %d or %x
17 unsigned int %u or %x
18 long %ld or %lx
19 unsigned long %lu or %lx
20 long long %lld or %llx
21 unsigned long long %llu or %llx
22 size_t %zu or %zx
23 ssize_t %zd or %zx
24 s32 %d or %x
25 u32 %u or %x
26 s64 %lld or %llx
27 u64 %llu or %llx
28
29
30If <type> is dependent on a config option for its size (e.g., sector_t,
31blkcnt_t) or is architecture-dependent for its size (e.g., tcflag_t), use a
32format specifier of its largest possible type and explicitly cast to it.
33
34Example::
35
36 printk("test: sector number/total blocks: %llu/%llu\n",
37 (unsigned long long)sector, (unsigned long long)blockcount);
38
39Reminder: sizeof() returns type size_t.
40
41The kernel's printf does not support %n. Floating point formats (%e, %f,
42%g, %a) are also not recognized, for obvious reasons. Use of any
43unsupported specifier or length qualifier results in a WARN and early
44return from vsnprintf().
45
46Pointer types
47=============
48
49A raw pointer value may be printed with %p which will hash the address
50before printing. The kernel also supports extended specifiers for printing
51pointers of different types.
52
53Plain Pointers
54--------------
55
56::
57
58 %p abcdef12 or 00000000abcdef12
59
60Pointers printed without a specifier extension (i.e unadorned %p) are
61hashed to prevent leaking information about the kernel memory layout. This
62has the added benefit of providing a unique identifier. On 64-bit machines
63the first 32 bits are zeroed. The kernel will print ``(ptrval)`` until it
64gathers enough entropy. If you *really* want the address see %px below.
65
66Symbols/Function Pointers
67-------------------------
68
69::
70
71 %pS versatile_init+0x0/0x110
72 %ps versatile_init
73 %pF versatile_init+0x0/0x110
74 %pf versatile_init
75 %pSR versatile_init+0x9/0x110
76 (with __builtin_extract_return_addr() translation)
77 %pB prev_fn_of_versatile_init+0x88/0x88
78
79
80The ``S`` and ``s`` specifiers are used for printing a pointer in symbolic
81format. They result in the symbol name with (S) or without (s)
82offsets. If KALLSYMS are disabled then the symbol address is printed instead.
83
84Note, that the ``F`` and ``f`` specifiers are identical to ``S`` (``s``)
85and thus deprecated. We have ``F`` and ``f`` because on ia64, ppc64 and
86parisc64 function pointers are indirect and, in fact, are function
87descriptors, which require additional dereferencing before we can lookup
88the symbol. As of now, ``S`` and ``s`` perform dereferencing on those
89platforms (when needed), so ``F`` and ``f`` exist for compatibility
90reasons only.
91
92The ``B`` specifier results in the symbol name with offsets and should be
93used when printing stack backtraces. The specifier takes into
94consideration the effect of compiler optimisations which may occur
95when tail-calls are used and marked with the noreturn GCC attribute.
96
97Kernel Pointers
98---------------
99
100::
101
102 %pK 01234567 or 0123456789abcdef
103
104For printing kernel pointers which should be hidden from unprivileged
105users. The behaviour of %pK depends on the kptr_restrict sysctl - see
106Documentation/sysctl/kernel.txt for more details.
107
108Unmodified Addresses
109--------------------
110
111::
112
113 %px 01234567 or 0123456789abcdef
114
115For printing pointers when you *really* want to print the address. Please
116consider whether or not you are leaking sensitive information about the
117kernel memory layout before printing pointers with %px. %px is functionally
118equivalent to %lx (or %lu). %px is preferred because it is more uniquely
119grep'able. If in the future we need to modify the way the kernel handles
120printing pointers we will be better equipped to find the call sites.
121
122Struct Resources
123----------------
124
125::
126
127 %pr [mem 0x60000000-0x6fffffff flags 0x2200] or
128 [mem 0x0000000060000000-0x000000006fffffff flags 0x2200]
129 %pR [mem 0x60000000-0x6fffffff pref] or
130 [mem 0x0000000060000000-0x000000006fffffff pref]
131
132For printing struct resources. The ``R`` and ``r`` specifiers result in a
133printed resource with (R) or without (r) a decoded flags member.
134
135Passed by reference.
136
137Physical address types phys_addr_t
138----------------------------------
139
140::
141
142 %pa[p] 0x01234567 or 0x0123456789abcdef
143
144For printing a phys_addr_t type (and its derivatives, such as
145resource_size_t) which can vary based on build options, regardless of the
146width of the CPU data path.
147
148Passed by reference.
149
150DMA address types dma_addr_t
151----------------------------
152
153::
154
155 %pad 0x01234567 or 0x0123456789abcdef
156
157For printing a dma_addr_t type which can vary based on build options,
158regardless of the width of the CPU data path.
159
160Passed by reference.
161
162Raw buffer as an escaped string
163-------------------------------
164
165::
166
167 %*pE[achnops]
168
169For printing raw buffer as an escaped string. For the following buffer::
170
171 1b 62 20 5c 43 07 22 90 0d 5d
172
173A few examples show how the conversion would be done (excluding surrounding
174quotes)::
175
176 %*pE "\eb \C\a"\220\r]"
177 %*pEhp "\x1bb \C\x07"\x90\x0d]"
178 %*pEa "\e\142\040\\\103\a\042\220\r\135"
179
180The conversion rules are applied according to an optional combination
181of flags (see :c:func:`string_escape_mem` kernel documentation for the
182details):
183
184 - a - ESCAPE_ANY
185 - c - ESCAPE_SPECIAL
186 - h - ESCAPE_HEX
187 - n - ESCAPE_NULL
188 - o - ESCAPE_OCTAL
189 - p - ESCAPE_NP
190 - s - ESCAPE_SPACE
191
192By default ESCAPE_ANY_NP is used.
193
194ESCAPE_ANY_NP is the sane choice for many cases, in particularly for
195printing SSIDs.
196
197If field width is omitted then 1 byte only will be escaped.
198
199Raw buffer as a hex string
200--------------------------
201
202::
203
204 %*ph 00 01 02 ... 3f
205 %*phC 00:01:02: ... :3f
206 %*phD 00-01-02- ... -3f
207 %*phN 000102 ... 3f
208
209For printing small buffers (up to 64 bytes long) as a hex string with a
210certain separator. For larger buffers consider using
211:c:func:`print_hex_dump`.
212
213MAC/FDDI addresses
214------------------
215
216::
217
218 %pM 00:01:02:03:04:05
219 %pMR 05:04:03:02:01:00
220 %pMF 00-01-02-03-04-05
221 %pm 000102030405
222 %pmR 050403020100
223
224For printing 6-byte MAC/FDDI addresses in hex notation. The ``M`` and ``m``
225specifiers result in a printed address with (M) or without (m) byte
226separators. The default byte separator is the colon (:).
227
228Where FDDI addresses are concerned the ``F`` specifier can be used after
229the ``M`` specifier to use dash (-) separators instead of the default
230separator.
231
232For Bluetooth addresses the ``R`` specifier shall be used after the ``M``
233specifier to use reversed byte order suitable for visual interpretation
234of Bluetooth addresses which are in the little endian order.
235
236Passed by reference.
237
238IPv4 addresses
239--------------
240
241::
242
243 %pI4 1.2.3.4
244 %pi4 001.002.003.004
245 %p[Ii]4[hnbl]
246
247For printing IPv4 dot-separated decimal addresses. The ``I4`` and ``i4``
248specifiers result in a printed address with (i4) or without (I4) leading
249zeros.
250
251The additional ``h``, ``n``, ``b``, and ``l`` specifiers are used to specify
252host, network, big or little endian order addresses respectively. Where
253no specifier is provided the default network/big endian order is used.
254
255Passed by reference.
256
257IPv6 addresses
258--------------
259
260::
261
262 %pI6 0001:0002:0003:0004:0005:0006:0007:0008
263 %pi6 00010002000300040005000600070008
264 %pI6c 1:2:3:4:5:6:7:8
265
266For printing IPv6 network-order 16-bit hex addresses. The ``I6`` and ``i6``
267specifiers result in a printed address with (I6) or without (i6)
268colon-separators. Leading zeros are always used.
269
270The additional ``c`` specifier can be used with the ``I`` specifier to
271print a compressed IPv6 address as described by
272http://tools.ietf.org/html/rfc5952
273
274Passed by reference.
275
276IPv4/IPv6 addresses (generic, with port, flowinfo, scope)
277---------------------------------------------------------
278
279::
280
281 %pIS 1.2.3.4 or 0001:0002:0003:0004:0005:0006:0007:0008
282 %piS 001.002.003.004 or 00010002000300040005000600070008
283 %pISc 1.2.3.4 or 1:2:3:4:5:6:7:8
284 %pISpc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345
285 %p[Ii]S[pfschnbl]
286
287For printing an IP address without the need to distinguish whether it's of
288type AF_INET or AF_INET6. A pointer to a valid struct sockaddr,
289specified through ``IS`` or ``iS``, can be passed to this format specifier.
290
291The additional ``p``, ``f``, and ``s`` specifiers are used to specify port
292(IPv4, IPv6), flowinfo (IPv6) and scope (IPv6). Ports have a ``:`` prefix,
293flowinfo a ``/`` and scope a ``%``, each followed by the actual value.
294
295In case of an IPv6 address the compressed IPv6 address as described by
296http://tools.ietf.org/html/rfc5952 is being used if the additional
297specifier ``c`` is given. The IPv6 address is surrounded by ``[``, ``]`` in
298case of additional specifiers ``p``, ``f`` or ``s`` as suggested by
299https://tools.ietf.org/html/draft-ietf-6man-text-addr-representation-07
300
301In case of IPv4 addresses, the additional ``h``, ``n``, ``b``, and ``l``
302specifiers can be used as well and are ignored in case of an IPv6
303address.
304
305Passed by reference.
306
307Further examples::
308
309 %pISfc 1.2.3.4 or [1:2:3:4:5:6:7:8]/123456789
310 %pISsc 1.2.3.4 or [1:2:3:4:5:6:7:8]%1234567890
311 %pISpfc 1.2.3.4:12345 or [1:2:3:4:5:6:7:8]:12345/123456789
312
313UUID/GUID addresses
314-------------------
315
316::
317
318 %pUb 00010203-0405-0607-0809-0a0b0c0d0e0f
319 %pUB 00010203-0405-0607-0809-0A0B0C0D0E0F
320 %pUl 03020100-0504-0706-0809-0a0b0c0e0e0f
321 %pUL 03020100-0504-0706-0809-0A0B0C0E0E0F
322
323For printing 16-byte UUID/GUIDs addresses. The additional ``l``, ``L``,
324``b`` and ``B`` specifiers are used to specify a little endian order in
325lower (l) or upper case (L) hex notation - and big endian order in lower (b)
326or upper case (B) hex notation.
327
328Where no additional specifiers are used the default big endian
329order with lower case hex notation will be printed.
330
331Passed by reference.
332
333dentry names
334------------
335
336::
337
338 %pd{,2,3,4}
339 %pD{,2,3,4}
340
341For printing dentry name; if we race with :c:func:`d_move`, the name might
342be a mix of old and new ones, but it won't oops. %pd dentry is a safer
343equivalent of %s dentry->d_name.name we used to use, %pd<n> prints ``n``
344last components. %pD does the same thing for struct file.
345
346Passed by reference.
347
348block_device names
349------------------
350
351::
352
353 %pg sda, sda1 or loop0p1
354
355For printing name of block_device pointers.
356
357struct va_format
358----------------
359
360::
361
362 %pV
363
364For printing struct va_format structures. These contain a format string
365and va_list as follows::
366
367 struct va_format {
368 const char *fmt;
369 va_list *va;
370 };
371
372Implements a "recursive vsnprintf".
373
374Do not use this feature without some mechanism to verify the
375correctness of the format string and va_list arguments.
376
377Passed by reference.
378
379kobjects
380--------
381
382::
383
384 %pOF[fnpPcCF]
385
386
387For printing kobject based structs (device nodes). Default behaviour is
388equivalent to %pOFf.
389
390 - f - device node full_name
391 - n - device node name
392 - p - device node phandle
393 - P - device node path spec (name + @unit)
394 - F - device node flags
395 - c - major compatible string
396 - C - full compatible string
397
398The separator when using multiple arguments is ':'
399
400Examples::
401
402 %pOF /foo/bar@0 - Node full name
403 %pOFf /foo/bar@0 - Same as above
404 %pOFfp /foo/bar@0:10 - Node full name + phandle
405 %pOFfcF /foo/bar@0:foo,device:--P- - Node full name +
406 major compatible string +
407 node flags
408 D - dynamic
409 d - detached
410 P - Populated
411 B - Populated bus
412
413Passed by reference.
414
415struct clk
416----------
417
418::
419
420 %pC pll1
421 %pCn pll1
422 %pCr 1560000000
423
424For printing struct clk structures. %pC and %pCn print the name
425(Common Clock Framework) or address (legacy clock framework) of the
426structure; %pCr prints the current clock rate.
427
428Passed by reference.
429
430bitmap and its derivatives such as cpumask and nodemask
431-------------------------------------------------------
432
433::
434
435 %*pb 0779
436 %*pbl 0,3-6,8-10
437
438For printing bitmap and its derivatives such as cpumask and nodemask,
439%*pb outputs the bitmap with field width as the number of bits and %*pbl
440output the bitmap as range list with field width as the number of bits.
441
442Passed by reference.
443
444Flags bitfields such as page flags, gfp_flags
445---------------------------------------------
446
447::
448
449 %pGp referenced|uptodate|lru|active|private
450 %pGg GFP_USER|GFP_DMA32|GFP_NOWARN
451 %pGv read|exec|mayread|maywrite|mayexec|denywrite
452
453For printing flags bitfields as a collection of symbolic constants that
454would construct the value. The type of flags is given by the third
455character. Currently supported are [p]age flags, [v]ma_flags (both
456expect ``unsigned long *``) and [g]fp_flags (expects ``gfp_t *``). The flag
457names and print order depends on the particular type.
458
459Note that this format should not be used directly in the
460:c:func:`TP_printk()` part of a tracepoint. Instead, use the show_*_flags()
461functions from <trace/events/mmflags.h>.
462
463Passed by reference.
464
465Network device features
466-----------------------
467
468::
469
470 %pNF 0x000000000000c000
471
472For printing netdev_features_t.
473
474Passed by reference.
475
476Thanks
477======
478
479If you add other %p extensions, please extend <lib/test_printf.c> with
480one or more test cases, if at all feasible.
481
482Thank you for your cooperation and attention.