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