1 Dynamic debug 1 Dynamic debug
2 +++++++++++++ 2 +++++++++++++
3 3
4 4
5 Introduction 5 Introduction
6 ============ 6 ============
7 7
8 Dynamic debug allows you to dynamically enable 8 Dynamic debug allows you to dynamically enable/disable kernel
9 debug-print code to obtain additional kernel i 9 debug-print code to obtain additional kernel information.
10 10
11 If ``/proc/dynamic_debug/control`` exists, you 11 If ``/proc/dynamic_debug/control`` exists, your kernel has dynamic
12 debug. You'll need root access (sudo su) to u 12 debug. You'll need root access (sudo su) to use this.
13 13
14 Dynamic debug provides: 14 Dynamic debug provides:
15 15
16 * a Catalog of all *prdbgs* in your kernel. 16 * a Catalog of all *prdbgs* in your kernel.
17 ``cat /proc/dynamic_debug/control`` to see 17 ``cat /proc/dynamic_debug/control`` to see them.
18 18
19 * a Simple query/command language to alter *p 19 * a Simple query/command language to alter *prdbgs* by selecting on
20 any combination of 0 or 1 of: 20 any combination of 0 or 1 of:
21 21
22 - source filename 22 - source filename
23 - function name 23 - function name
24 - line number (including ranges of line num 24 - line number (including ranges of line numbers)
25 - module name 25 - module name
26 - format string 26 - format string
27 - class name (as known/declared by each mod 27 - class name (as known/declared by each module)
28 28
29 NOTE: To actually get the debug-print output o 29 NOTE: To actually get the debug-print output on the console, you may
30 need to adjust the kernel ``loglevel=``, or us 30 need to adjust the kernel ``loglevel=``, or use ``ignore_loglevel``.
31 Read about these kernel parameters in 31 Read about these kernel parameters in
32 Documentation/admin-guide/kernel-parameters.rs 32 Documentation/admin-guide/kernel-parameters.rst.
33 33
34 Viewing Dynamic Debug Behaviour 34 Viewing Dynamic Debug Behaviour
35 =============================== 35 ===============================
36 36
37 You can view the currently configured behaviou 37 You can view the currently configured behaviour in the *prdbg* catalog::
38 38
39 :#> head -n7 /proc/dynamic_debug/control 39 :#> head -n7 /proc/dynamic_debug/control
40 # filename:lineno [module]function flags for 40 # filename:lineno [module]function flags format
41 init/main.c:1179 [main]initcall_blacklist =_ 41 init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\012
42 init/main.c:1218 [main]initcall_blacklisted 42 init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\012"
43 init/main.c:1424 [main]run_init_process =_ " 43 init/main.c:1424 [main]run_init_process =_ " with arguments:\012"
44 init/main.c:1426 [main]run_init_process =_ " 44 init/main.c:1426 [main]run_init_process =_ " %s\012"
45 init/main.c:1427 [main]run_init_process =_ " 45 init/main.c:1427 [main]run_init_process =_ " with environment:\012"
46 init/main.c:1429 [main]run_init_process =_ " 46 init/main.c:1429 [main]run_init_process =_ " %s\012"
47 47
48 The 3rd space-delimited column shows the curre 48 The 3rd space-delimited column shows the current flags, preceded by
49 a ``=`` for easy use with grep/cut. ``=p`` sho 49 a ``=`` for easy use with grep/cut. ``=p`` shows enabled callsites.
50 50
51 Controlling dynamic debug Behaviour 51 Controlling dynamic debug Behaviour
52 =================================== 52 ===================================
53 53
54 The behaviour of *prdbg* sites are controlled 54 The behaviour of *prdbg* sites are controlled by writing
55 query/commands to the control file. Example:: 55 query/commands to the control file. Example::
56 56
57 # grease the interface 57 # grease the interface
58 :#> alias ddcmd='echo $* > /proc/dynamic_deb 58 :#> alias ddcmd='echo $* > /proc/dynamic_debug/control'
59 59
60 :#> ddcmd '-p; module main func run* +p' 60 :#> ddcmd '-p; module main func run* +p'
61 :#> grep =p /proc/dynamic_debug/control 61 :#> grep =p /proc/dynamic_debug/control
62 init/main.c:1424 [main]run_init_process =p " 62 init/main.c:1424 [main]run_init_process =p " with arguments:\012"
63 init/main.c:1426 [main]run_init_process =p " 63 init/main.c:1426 [main]run_init_process =p " %s\012"
64 init/main.c:1427 [main]run_init_process =p " 64 init/main.c:1427 [main]run_init_process =p " with environment:\012"
65 init/main.c:1429 [main]run_init_process =p " 65 init/main.c:1429 [main]run_init_process =p " %s\012"
66 66
67 Error messages go to console/syslog:: 67 Error messages go to console/syslog::
68 68
69 :#> ddcmd mode foo +p 69 :#> ddcmd mode foo +p
70 dyndbg: unknown keyword "mode" 70 dyndbg: unknown keyword "mode"
71 dyndbg: query parse failed 71 dyndbg: query parse failed
72 bash: echo: write error: Invalid argument 72 bash: echo: write error: Invalid argument
73 73
74 If debugfs is also enabled and mounted, ``dyna 74 If debugfs is also enabled and mounted, ``dynamic_debug/control`` is
75 also under the mount-dir, typically ``/sys/ker 75 also under the mount-dir, typically ``/sys/kernel/debug/``.
76 76
77 Command Language Reference 77 Command Language Reference
78 ========================== 78 ==========================
79 79
80 At the basic lexical level, a command is a seq 80 At the basic lexical level, a command is a sequence of words separated
81 by spaces or tabs. So these are all equivalen 81 by spaces or tabs. So these are all equivalent::
82 82
83 :#> ddcmd file svcsock.c line 1603 +p 83 :#> ddcmd file svcsock.c line 1603 +p
84 :#> ddcmd "file svcsock.c line 1603 +p" 84 :#> ddcmd "file svcsock.c line 1603 +p"
85 :#> ddcmd ' file svcsock.c line 1603 85 :#> ddcmd ' file svcsock.c line 1603 +p '
86 86
87 Command submissions are bounded by a write() s 87 Command submissions are bounded by a write() system call.
88 Multiple commands can be written together, sep 88 Multiple commands can be written together, separated by ``;`` or ``\n``::
89 89
90 :#> ddcmd "func pnpacpi_get_resources +p; fu 90 :#> ddcmd "func pnpacpi_get_resources +p; func pnp_assign_mem +p"
91 :#> ddcmd <<"EOC" 91 :#> ddcmd <<"EOC"
92 func pnpacpi_get_resources +p 92 func pnpacpi_get_resources +p
93 func pnp_assign_mem +p 93 func pnp_assign_mem +p
94 EOC 94 EOC
95 :#> cat query-batch-file > /proc/dynamic_deb 95 :#> cat query-batch-file > /proc/dynamic_debug/control
96 96
97 You can also use wildcards in each query term. 97 You can also use wildcards in each query term. The match rule supports
98 ``*`` (matches zero or more characters) and `` 98 ``*`` (matches zero or more characters) and ``?`` (matches exactly one
99 character). For example, you can match all usb 99 character). For example, you can match all usb drivers::
100 100
101 :#> ddcmd file "drivers/usb/*" +p # "" t 101 :#> ddcmd file "drivers/usb/*" +p # "" to suppress shell expansion
102 102
103 Syntactically, a command is pairs of keyword v 103 Syntactically, a command is pairs of keyword values, followed by a
104 flags change or setting:: 104 flags change or setting::
105 105
106 command ::= match-spec* flags-spec 106 command ::= match-spec* flags-spec
107 107
108 The match-spec's select *prdbgs* from the cata 108 The match-spec's select *prdbgs* from the catalog, upon which to apply
109 the flags-spec, all constraints are ANDed toge 109 the flags-spec, all constraints are ANDed together. An absent keyword
110 is the same as keyword "*". 110 is the same as keyword "*".
111 111
112 112
113 A match specification is a keyword, which sele 113 A match specification is a keyword, which selects the attribute of
114 the callsite to be compared, and a value to co 114 the callsite to be compared, and a value to compare against. Possible
115 keywords are::: 115 keywords are:::
116 116
117 match-spec ::= 'func' string | 117 match-spec ::= 'func' string |
118 'file' string | 118 'file' string |
119 'module' string | 119 'module' string |
120 'format' string | 120 'format' string |
121 'class' string | 121 'class' string |
122 'line' line-range 122 'line' line-range
123 123
124 line-range ::= lineno | 124 line-range ::= lineno |
125 '-'lineno | 125 '-'lineno |
126 lineno'-' | 126 lineno'-' |
127 lineno'-'lineno 127 lineno'-'lineno
128 128
129 lineno ::= unsigned-int 129 lineno ::= unsigned-int
130 130
131 .. note:: 131 .. note::
132 132
133 ``line-range`` cannot contain space, e.g. 133 ``line-range`` cannot contain space, e.g.
134 "1-30" is valid range but "1 - 30" is not. 134 "1-30" is valid range but "1 - 30" is not.
135 135
136 136
137 The meanings of each keyword are: 137 The meanings of each keyword are:
138 138
139 func 139 func
140 The given string is compared against the f 140 The given string is compared against the function name
141 of each callsite. Example:: 141 of each callsite. Example::
142 142
143 func svc_tcp_accept 143 func svc_tcp_accept
144 func *recv* # in rfcomm, b 144 func *recv* # in rfcomm, bluetooth, ping, tcp
145 145
146 file 146 file
147 The given string is compared against eithe 147 The given string is compared against either the src-root relative
148 pathname, or the basename of the source fi 148 pathname, or the basename of the source file of each callsite.
149 Examples:: 149 Examples::
150 150
151 file svcsock.c 151 file svcsock.c
152 file kernel/freezer.c # ie column 1 152 file kernel/freezer.c # ie column 1 of control file
153 file drivers/usb/* # all callsite 153 file drivers/usb/* # all callsites under it
154 file inode.c:start_* # parse :tail 154 file inode.c:start_* # parse :tail as a func (above)
155 file inode.c:1-100 # parse :tail 155 file inode.c:1-100 # parse :tail as a line-range (above)
156 156
157 module 157 module
158 The given string is compared against the m 158 The given string is compared against the module name
159 of each callsite. The module name is the 159 of each callsite. The module name is the string as
160 seen in ``lsmod``, i.e. without the direct 160 seen in ``lsmod``, i.e. without the directory or the ``.ko``
161 suffix and with ``-`` changed to ``_``. E 161 suffix and with ``-`` changed to ``_``. Examples::
162 162
163 module sunrpc 163 module sunrpc
164 module nfsd 164 module nfsd
165 module drm* # both drm, drm_kms_he 165 module drm* # both drm, drm_kms_helper
166 166
167 format 167 format
168 The given string is searched for in the dy 168 The given string is searched for in the dynamic debug format
169 string. Note that the string does not nee 169 string. Note that the string does not need to match the
170 entire format, only some part. Whitespace 170 entire format, only some part. Whitespace and other
171 special characters can be escaped using C 171 special characters can be escaped using C octal character
172 escape ``\ooo`` notation, e.g. the space c 172 escape ``\ooo`` notation, e.g. the space character is ``\040``.
173 Alternatively, the string can be enclosed 173 Alternatively, the string can be enclosed in double quote
174 characters (``"``) or single quote charact 174 characters (``"``) or single quote characters (``'``).
175 Examples:: 175 Examples::
176 176
177 format svcrdma: // many of the 177 format svcrdma: // many of the NFS/RDMA server pr_debugs
178 format readahead // some pr_deb 178 format readahead // some pr_debugs in the readahead cache
179 format nfsd:\040SETATTR // one way to 179 format nfsd:\040SETATTR // one way to match a format with whitespace
180 format "nfsd: SETATTR" // a neater wa 180 format "nfsd: SETATTR" // a neater way to match a format with whitespace
181 format 'nfsd: SETATTR' // yet another 181 format 'nfsd: SETATTR' // yet another way to match a format with whitespace
182 182
183 class 183 class
184 The given class_name is validated against 184 The given class_name is validated against each module, which may
185 have declared a list of known class_names. 185 have declared a list of known class_names. If the class_name is
186 found for a module, callsite & class match 186 found for a module, callsite & class matching and adjustment
187 proceeds. Examples:: 187 proceeds. Examples::
188 188
189 class DRM_UT_KMS # a DRM.debug 189 class DRM_UT_KMS # a DRM.debug category
190 class JUNK # silent non-m 190 class JUNK # silent non-match
191 // class TLD_* # NOTICE: no w 191 // class TLD_* # NOTICE: no wildcard in class names
192 192
193 line 193 line
194 The given line number or range of line num 194 The given line number or range of line numbers is compared
195 against the line number of each ``pr_debug 195 against the line number of each ``pr_debug()`` callsite. A single
196 line number matches the callsite line numb 196 line number matches the callsite line number exactly. A
197 range of line numbers matches any callsite 197 range of line numbers matches any callsite between the first
198 and last line number inclusive. An empty 198 and last line number inclusive. An empty first number means
199 the first line in the file, an empty last 199 the first line in the file, an empty last line number means the
200 last line number in the file. Examples:: 200 last line number in the file. Examples::
201 201
202 line 1603 // exactly line 16 202 line 1603 // exactly line 1603
203 line 1600-1605 // the six lines f 203 line 1600-1605 // the six lines from line 1600 to line 1605
204 line -1605 // the 1605 lines 204 line -1605 // the 1605 lines from line 1 to line 1605
205 line 1600- // all lines from 205 line 1600- // all lines from line 1600 to the end of the file
206 206
207 The flags specification comprises a change ope 207 The flags specification comprises a change operation followed
208 by one or more flag characters. The change op 208 by one or more flag characters. The change operation is one
209 of the characters:: 209 of the characters::
210 210
211 - remove the given flags 211 - remove the given flags
212 + add the given flags 212 + add the given flags
213 = set the flags to the given flags 213 = set the flags to the given flags
214 214
215 The flags are:: 215 The flags are::
216 216
217 p enables the pr_debug() callsite. 217 p enables the pr_debug() callsite.
218 _ enables no flags. 218 _ enables no flags.
219 219
220 Decorator flags add to the message-prefix, i 220 Decorator flags add to the message-prefix, in order:
221 t Include thread ID, or <intr> 221 t Include thread ID, or <intr>
222 m Include module name 222 m Include module name
223 f Include the function name 223 f Include the function name
224 s Include the source file name 224 s Include the source file name
225 l Include line number 225 l Include line number
226 226
227 For ``print_hex_dump_debug()`` and ``print_hex 227 For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
228 the ``p`` flag has meaning, other flags are ig 228 the ``p`` flag has meaning, other flags are ignored.
229 229
230 Note the regexp ``^[-+=][fslmpt_]+$`` matches 230 Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification.
231 To clear all flags at once, use ``=_`` or ``-f 231 To clear all flags at once, use ``=_`` or ``-fslmpt``.
232 232
233 233
234 Debug messages during Boot Process 234 Debug messages during Boot Process
235 ================================== 235 ==================================
236 236
237 To activate debug messages for core code and b 237 To activate debug messages for core code and built-in modules during
238 the boot process, even before userspace and de 238 the boot process, even before userspace and debugfs exists, use
239 ``dyndbg="QUERY"`` or ``module.dyndbg="QUERY"` 239 ``dyndbg="QUERY"`` or ``module.dyndbg="QUERY"``. QUERY follows
240 the syntax described above, but must not excee 240 the syntax described above, but must not exceed 1023 characters. Your
241 bootloader may impose lower limits. 241 bootloader may impose lower limits.
242 242
243 These ``dyndbg`` params are processed just aft 243 These ``dyndbg`` params are processed just after the ddebug tables are
244 processed, as part of the early_initcall. Thu 244 processed, as part of the early_initcall. Thus you can enable debug
245 messages in all code run after this early_init 245 messages in all code run after this early_initcall via this boot
246 parameter. 246 parameter.
247 247
248 On an x86 system for example ACPI enablement i 248 On an x86 system for example ACPI enablement is a subsys_initcall and::
249 249
250 dyndbg="file ec.c +p" 250 dyndbg="file ec.c +p"
251 251
252 will show early Embedded Controller transactio 252 will show early Embedded Controller transactions during ACPI setup if
253 your machine (typically a laptop) has an Embed 253 your machine (typically a laptop) has an Embedded Controller.
254 PCI (or other devices) initialization also is 254 PCI (or other devices) initialization also is a hot candidate for using
255 this boot parameter for debugging purposes. 255 this boot parameter for debugging purposes.
256 256
257 If ``foo`` module is not built-in, ``foo.dyndb 257 If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at
258 boot time, without effect, but will be reproce 258 boot time, without effect, but will be reprocessed when module is
259 loaded later. Bare ``dyndbg=`` is only process 259 loaded later. Bare ``dyndbg=`` is only processed at boot.
260 260
261 261
262 Debug Messages at Module Initialization Time 262 Debug Messages at Module Initialization Time
263 ============================================ 263 ============================================
264 264
265 When ``modprobe foo`` is called, modprobe scan 265 When ``modprobe foo`` is called, modprobe scans ``/proc/cmdline`` for
266 ``foo.params``, strips ``foo.``, and passes th 266 ``foo.params``, strips ``foo.``, and passes them to the kernel along with
267 params given in modprobe args or ``/etc/modpro 267 params given in modprobe args or ``/etc/modprobe.d/*.conf`` files,
268 in the following order: 268 in the following order:
269 269
270 1. parameters given via ``/etc/modprobe.d/*.co 270 1. parameters given via ``/etc/modprobe.d/*.conf``::
271 271
272 options foo dyndbg=+pt 272 options foo dyndbg=+pt
273 options foo dyndbg # defaults to +p 273 options foo dyndbg # defaults to +p
274 274
275 2. ``foo.dyndbg`` as given in boot args, ``foo 275 2. ``foo.dyndbg`` as given in boot args, ``foo.`` is stripped and passed::
276 276
277 foo.dyndbg=" func bar +p; func buz +mp 277 foo.dyndbg=" func bar +p; func buz +mp"
278 278
279 3. args to modprobe:: 279 3. args to modprobe::
280 280
281 modprobe foo dyndbg==pmf # override pr 281 modprobe foo dyndbg==pmf # override previous settings
282 282
283 These ``dyndbg`` queries are applied in order, 283 These ``dyndbg`` queries are applied in order, with last having final say.
284 This allows boot args to override or modify th 284 This allows boot args to override or modify those from ``/etc/modprobe.d``
285 (sensible, since 1 is system wide, 2 is kernel 285 (sensible, since 1 is system wide, 2 is kernel or boot specific), and
286 modprobe args to override both. 286 modprobe args to override both.
287 287
288 In the ``foo.dyndbg="QUERY"`` form, the query 288 In the ``foo.dyndbg="QUERY"`` form, the query must exclude ``module foo``.
289 ``foo`` is extracted from the param-name, and 289 ``foo`` is extracted from the param-name, and applied to each query in
290 ``QUERY``, and only 1 match-spec of each type 290 ``QUERY``, and only 1 match-spec of each type is allowed.
291 291
292 The ``dyndbg`` option is a "fake" module param 292 The ``dyndbg`` option is a "fake" module parameter, which means:
293 293
294 - modules do not need to define it explicitly 294 - modules do not need to define it explicitly
295 - every module gets it tacitly, whether they u 295 - every module gets it tacitly, whether they use pr_debug or not
296 - it doesn't appear in ``/sys/module/$module/p 296 - it doesn't appear in ``/sys/module/$module/parameters/``
297 To see it, grep the control file, or inspect 297 To see it, grep the control file, or inspect ``/proc/cmdline.``
298 298
299 For ``CONFIG_DYNAMIC_DEBUG`` kernels, any sett 299 For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or
300 enabled by ``-DDEBUG`` flag during compilation 300 enabled by ``-DDEBUG`` flag during compilation) can be disabled later via
301 the debugfs interface if the debug messages ar 301 the debugfs interface if the debug messages are no longer needed::
302 302
303 echo "module module_name -p" > /proc/dynami 303 echo "module module_name -p" > /proc/dynamic_debug/control
304 304
305 Examples 305 Examples
306 ======== 306 ========
307 307
308 :: 308 ::
309 309
310 // enable the message at line 1603 of file s 310 // enable the message at line 1603 of file svcsock.c
311 :#> ddcmd 'file svcsock.c line 1603 +p' 311 :#> ddcmd 'file svcsock.c line 1603 +p'
312 312
313 // enable all the messages in file svcsock.c 313 // enable all the messages in file svcsock.c
314 :#> ddcmd 'file svcsock.c +p' 314 :#> ddcmd 'file svcsock.c +p'
315 315
316 // enable all the messages in the NFS server 316 // enable all the messages in the NFS server module
317 :#> ddcmd 'module nfsd +p' 317 :#> ddcmd 'module nfsd +p'
318 318
319 // enable all 12 messages in the function sv 319 // enable all 12 messages in the function svc_process()
320 :#> ddcmd 'func svc_process +p' 320 :#> ddcmd 'func svc_process +p'
321 321
322 // disable all 12 messages in the function s 322 // disable all 12 messages in the function svc_process()
323 :#> ddcmd 'func svc_process -p' 323 :#> ddcmd 'func svc_process -p'
324 324
325 // enable messages for NFS calls READ, READL 325 // enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
326 :#> ddcmd 'format "nfsd: READ" +p' 326 :#> ddcmd 'format "nfsd: READ" +p'
327 327
328 // enable messages in files of which the pat 328 // enable messages in files of which the paths include string "usb"
329 :#> ddcmd 'file *usb* +p' 329 :#> ddcmd 'file *usb* +p'
330 330
331 // enable all messages 331 // enable all messages
332 :#> ddcmd '+p' 332 :#> ddcmd '+p'
333 333
334 // add module, function to all enabled messa 334 // add module, function to all enabled messages
335 :#> ddcmd '+mf' 335 :#> ddcmd '+mf'
336 336
337 // boot-args example, with newlines and comm 337 // boot-args example, with newlines and comments for readability
338 Kernel command line: ... 338 Kernel command line: ...
339 // see what's going on in dyndbg=value pro 339 // see what's going on in dyndbg=value processing
340 dynamic_debug.verbose=3 340 dynamic_debug.verbose=3
341 // enable pr_debugs in the btrfs module (c 341 // enable pr_debugs in the btrfs module (can be builtin or loadable)
342 btrfs.dyndbg="+p" 342 btrfs.dyndbg="+p"
343 // enable pr_debugs in all files under ini 343 // enable pr_debugs in all files under init/
344 // and the function parse_one, #cmt is str 344 // and the function parse_one, #cmt is stripped
345 dyndbg="file init/* +p #cmt ; func parse_o 345 dyndbg="file init/* +p #cmt ; func parse_one +p"
346 // enable pr_debugs in 2 functions in a mo 346 // enable pr_debugs in 2 functions in a module loaded later
347 pc87360.dyndbg="func pc87360_init_device + 347 pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"
348 348
349 Kernel Configuration 349 Kernel Configuration
350 ==================== 350 ====================
351 351
352 Dynamic Debug is enabled via kernel config ite 352 Dynamic Debug is enabled via kernel config items::
353 353
354 CONFIG_DYNAMIC_DEBUG=y # build catalo 354 CONFIG_DYNAMIC_DEBUG=y # build catalog, enables CORE
355 CONFIG_DYNAMIC_DEBUG_CORE=y # enable mecha 355 CONFIG_DYNAMIC_DEBUG_CORE=y # enable mechanics only, skip catalog
356 356
357 If you do not want to enable dynamic debug glo 357 If you do not want to enable dynamic debug globally (i.e. in some embedded
358 system), you may set ``CONFIG_DYNAMIC_DEBUG_CO 358 system), you may set ``CONFIG_DYNAMIC_DEBUG_CORE`` as basic support of dynamic
359 debug and add ``ccflags := -DDYNAMIC_DEBUG_MOD 359 debug and add ``ccflags := -DDYNAMIC_DEBUG_MODULE`` into the Makefile of any
360 modules which you'd like to dynamically debug 360 modules which you'd like to dynamically debug later.
361 361
362 362
363 Kernel *prdbg* API 363 Kernel *prdbg* API
364 ================== 364 ==================
365 365
366 The following functions are cataloged and cont 366 The following functions are cataloged and controllable when dynamic
367 debug is enabled:: 367 debug is enabled::
368 368
369 pr_debug() 369 pr_debug()
370 dev_dbg() 370 dev_dbg()
371 print_hex_dump_debug() 371 print_hex_dump_debug()
372 print_hex_dump_bytes() 372 print_hex_dump_bytes()
373 373
374 Otherwise, they are off by default; ``ccflags 374 Otherwise, they are off by default; ``ccflags += -DDEBUG`` or
375 ``#define DEBUG`` in a source file will enable 375 ``#define DEBUG`` in a source file will enable them appropriately.
376 376
377 If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``prin 377 If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is
378 just a shortcut for ``print_hex_dump(KERN_DEBU 378 just a shortcut for ``print_hex_dump(KERN_DEBUG)``.
379 379
380 For ``print_hex_dump_debug()``/``print_hex_dum 380 For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
381 its ``prefix_str`` argument, if it is constant 381 its ``prefix_str`` argument, if it is constant string; or ``hexdump``
382 in case ``prefix_str`` is built dynamically. 382 in case ``prefix_str`` is built dynamically.
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