1PERF-PROBE(1)                     perf Manual                    PERF-PROBE(1)
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NAME

6       perf-probe - Define new dynamic tracepoints
7

SYNOPSIS

9       perf probe [options] --add=PROBE [...]
10       or
11       perf probe [options] PROBE
12       or
13       perf probe [options] --del=[GROUP:]EVENT [...]
14       or
15       perf probe --list[=[GROUP:]EVENT]
16       or
17       perf probe [options] --line=LINE
18       or
19       perf probe [options] --vars=PROBEPOINT
20       or
21       perf probe [options] --funcs
22       or
23       perf probe [options] --definition=PROBE [...]
24

DESCRIPTION

26       This command defines dynamic tracepoint events, by symbol and registers
27       without debuginfo, or by C expressions (C line numbers, C function
28       names, and C local variables) with debuginfo.
29

OPTIONS

31       -k, --vmlinux=PATH
32           Specify vmlinux path which has debuginfo (Dwarf binary). Only when
33           using this with --definition, you can give an offline vmlinux file.
34
35       -m, --module=MODNAME|PATH
36           Specify module name in which perf-probe searches probe points or
37           lines. If a path of module file is passed, perf-probe treat it as
38           an offline module (this means you can add a probe on a module which
39           has not been loaded yet).
40
41       -s, --source=PATH
42           Specify path to kernel source.
43
44       -v, --verbose
45           Be more verbose (show parsed arguments, etc). Can not use with -q.
46
47       -q, --quiet
48           Be quiet (do not show any messages including errors). Can not use
49           with -v.
50
51       -a, --add=
52           Define a probe event (see PROBE SYNTAX for detail).
53
54       -d, --del=
55           Delete probe events. This accepts glob wildcards(*, ?) and
56           character classes(e.g. [a-z], [!A-Z]).
57
58       -l, --list[=[GROUP:]EVENT]
59           List up current probe events. This can also accept filtering
60           patterns of event names. When this is used with --cache, perf shows
61           all cached probes instead of the live probes.
62
63       -L, --line=
64           Show source code lines which can be probed. This needs an argument
65           which specifies a range of the source code. (see LINE SYNTAX for
66           detail)
67
68       -V, --vars=
69           Show available local variables at given probe point. The argument
70           syntax is same as PROBE SYNTAX, but NO ARGs.
71
72       --externs
73           (Only for --vars) Show external defined variables in addition to
74           local variables.
75
76       --no-inlines
77           (Only for --add) Search only for non-inlined functions. The
78           functions which do not have instances are ignored.
79
80       -F, --funcs[=FILTER]
81           Show available functions in given module or kernel. With -x/--exec,
82           can also list functions in a user space executable / shared
83           library. This also can accept a FILTER rule argument.
84
85       -D, --definition=
86           Show trace-event definition converted from given probe-event
87           instead of write it into tracing/[k,u]probe_events.
88
89       --filter=FILTER
90           (Only for --vars and --funcs) Set filter. FILTER is a combination
91           of glob pattern, see FILTER PATTERN for detail. Default FILTER is
92           "!k???tab_* & !crc_*" for --vars, and "!_*" for --funcs. If several
93           filters are specified, only the last filter is used.
94
95       -f, --force
96           Forcibly add events with existing name.
97
98       -n, --dry-run
99           Dry run. With this option, --add and --del doesn’t execute actual
100           adding and removal operations.
101
102       --cache
103           (With --add) Cache the probes. Any events which successfully added
104           are also stored in the cache file. (With --list) Show cached
105           probes. (With --del) Remove cached probes.
106
107       --max-probes=NUM
108           Set the maximum number of probe points for an event. Default is
109           128.
110
111       --target-ns=PID: Obtain mount namespace information from the target
112       pid. This is used when creating a uprobe for a process that resides in
113       a different mount namespace from the perf(1) utility.
114
115       -x, --exec=PATH
116           Specify path to the executable or shared library file for user
117           space tracing. Can also be used with --funcs option.
118
119       --demangle
120           Demangle application symbols. --no-demangle is also available for
121           disabling demangling.
122
123       --demangle-kernel
124           Demangle kernel symbols. --no-demangle-kernel is also available for
125           disabling kernel demangling.
126
127       In absence of -m/-x options, perf probe checks if the first argument
128       after the options is an absolute path name. If its an absolute path,
129       perf probe uses it as a target module/target user space binary to
130       probe.
131

PROBE SYNTAX

133       Probe points are defined by following syntax.
134
135           1) Define event based on function name
136            [[GROUP:]EVENT=]FUNC[@SRC][:RLN|+OFFS|%return|;PTN] [ARG ...]
137
138           2) Define event based on source file with line number
139            [[GROUP:]EVENT=]SRC:ALN [ARG ...]
140
141           3) Define event based on source file with lazy pattern
142            [[GROUP:]EVENT=]SRC;PTN [ARG ...]
143
144           4) Pre-defined SDT events or cached event with name
145            %[sdt_PROVIDER:]SDTEVENT
146            or,
147            sdt_PROVIDER:SDTEVENT
148
149       EVENT specifies the name of new event, if omitted, it will be set the
150       name of the probed function, and for return probes, a "__return" suffix
151       is automatically added to the function name. You can also specify a
152       group name by GROUP, if omitted, set probe is used for kprobe and
153       probe_<bin> is used for uprobe. Note that using existing group name can
154       conflict with other events. Especially, using the group name reserved
155       for kernel modules can hide embedded events in the modules. FUNC
156       specifies a probed function name, and it may have one of the following
157       options; +OFFS is the offset from function entry address in bytes, :RLN
158       is the relative-line number from function entry line, and %return means
159       that it probes function return. And ;PTN means lazy matching pattern
160       (see LAZY MATCHING). Note that ;PTN must be the end of the probe point
161       definition. In addition, @SRC specifies a source file which has that
162       function. It is also possible to specify a probe point by the source
163       line number or lazy matching by using SRC:ALN or SRC;PTN syntax, where
164       SRC is the source file path, :ALN is the line number and ;PTN is the
165       lazy matching pattern. ARG specifies the arguments of this probe point,
166       (see PROBE ARGUMENT). SDTEVENT and PROVIDER is the pre-defined event
167       name which is defined by user SDT (Statically Defined Tracing) or the
168       pre-cached probes with event name. Note that before using the SDT
169       event, the target binary (on which SDT events are defined) must be
170       scanned by perf-buildid-cache(1) to make SDT events as cached events.
171
172       For details of the SDT, see below.
173       https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html
174

ESCAPED CHARACTER

176       In the probe syntax, =, @, +, : and ; are treated as a special
177       character. You can use a backslash (\) to escape the special
178       characters. This is useful if you need to probe on a specific versioned
179       symbols, like @GLIBC_... suffixes, or also you need to specify a source
180       file which includes the special characters. Note that usually single
181       backslash is consumed by shell, so you might need to pass double
182       backslash (\\) or wrapping with single quotes ('AAA\@BBB'). See
183       EXAMPLES how it is used.
184

PROBE ARGUMENT

186       Each probe argument follows below syntax.
187
188           [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE][@user]
189
190       NAME specifies the name of this argument (optional). You can use the
191       name of local variable, local data structure member (e.g. var→field,
192       var.field2), local array with fixed index (e.g. array[1], var→array[0],
193       var→pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax,
194       etc). Note that the name of this argument will be set as the last
195       member name if you specify a local data structure member (e.g. field2
196       for var→field1.field2.) $vars and $params special arguments are also
197       available for NAME, $vars is expanded to the local variables (including
198       function parameters) which can access at given probe point. $params is
199       expanded to only the function parameters. TYPE casts the type of this
200       argument (optional). If omitted, perf probe automatically set the type
201       based on debuginfo (*). Currently, basic types
202       (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal integers
203       (x/x8/x16/x32/x64), signedness casting (u/s), "string" and bitfield are
204       supported. (see TYPES for detail) On x86 systems %REG is always the
205       short form of the register: for example %AX. %RAX or %EAX is not valid.
206       "@user" is a special attribute which means the LOCALVAR will be treated
207       as a user-space memory. This is only valid for kprobe event.
208

TYPES

210       Basic types (u8/u16/u32/u64/s8/s16/s32/s64) and hexadecimal integers
211       (x8/x16/x32/x64) are integer types. Prefix s and u means those types
212       are signed and unsigned respectively, and x means that is shown in
213       hexadecimal format. Traced arguments are shown in decimal (sNN/uNN) or
214       hex (xNN). You can also use s or u to specify only signedness and leave
215       its size auto-detected by perf probe. Moreover, you can use x to
216       explicitly specify to be shown in hexadecimal (the size is also
217       auto-detected). String type is a special type, which fetches a
218       "null-terminated" string from kernel space. This means it will fail and
219       store NULL if the string container has been paged out. You can specify
220       string type only for the local variable or structure member which is an
221       array of or a pointer to char or unsigned char type. Bitfield is
222       another special type, which takes 3 parameters, bit-width, bit-offset,
223       and container-size (usually 32). The syntax is;
224
225           b<bit-width>@<bit-offset>/<container-size>
226

LINE SYNTAX

228       Line range is described by following syntax.
229
230           "FUNC[@SRC][:RLN[+NUM|-RLN2]]|SRC[:ALN[+NUM|-ALN2]]"
231
232       FUNC specifies the function name of showing lines. RLN is the start
233       line number from function entry line, and RLN2 is the end line number.
234       As same as probe syntax, SRC means the source file path, ALN is start
235       line number, and ALN2 is end line number in the file. It is also
236       possible to specify how many lines to show by using NUM. Moreover,
237       FUNC@SRC combination is good for searching a specific function when
238       several functions share same name. So, "source.c:100-120" shows lines
239       between 100th to l20th in source.c file. And "func:10+20" shows 20
240       lines from 10th line of func function.
241

LAZY MATCHING

243       The lazy line matching is similar to glob matching but ignoring spaces
244       in both of pattern and target. So this accepts wildcards(*, ?) and
245       character classes(e.g. [a-z], [!A-Z]).
246
247       e.g. a=* can matches a=b, a = b, a == b and so on.
248
249       This provides some sort of flexibility and robustness to probe point
250       definitions against minor code changes. For example, actual 10th line
251       of schedule() can be moved easily by modifying schedule(), but the same
252       line matching rq=cpu_rq* may still exist in the function.)
253

FILTER PATTERN

255       The filter pattern is a glob matching pattern(s) to filter variables.
256       In addition, you can use "!" for specifying filter-out rule. You also
257       can give several rules combined with "&" or "|", and fold those rules
258       as one rule by using "(" ")".
259
260       e.g. With --filter "foo* | bar*", perf probe -V shows variables which
261       start with "foo" or "bar". With --filter "!foo* & *bar", perf probe -V
262       shows variables which don’t start with "foo" and end with "bar", like
263       "fizzbar". But "foobar" is filtered out.
264

EXAMPLES

266       Display which lines in schedule() can be probed:
267
268           ./perf probe --line schedule
269
270       Add a probe on schedule() function 12th line with recording cpu local
271       variable:
272
273           ./perf probe schedule:12 cpu
274           or
275           ./perf probe --add='schedule:12 cpu'
276
277       Add one or more probes which has the name start with "schedule".
278
279           ./perf probe schedule*
280           or
281           ./perf probe --add='schedule*'
282
283       Add probes on lines in schedule() function which calls
284       update_rq_clock().
285
286           ./perf probe 'schedule;update_rq_clock*'
287           or
288           ./perf probe --add='schedule;update_rq_clock*'
289
290       Delete all probes on schedule().
291
292           ./perf probe --del='schedule*'
293
294       Add probes at zfree() function on /bin/zsh
295
296           ./perf probe -x /bin/zsh zfree or ./perf probe /bin/zsh zfree
297
298       Add probes at malloc() function on libc
299
300           ./perf probe -x /lib/libc.so.6 malloc or ./perf probe /lib/libc.so.6 malloc
301
302       Add a uprobe to a target process running in a different mount namespace
303
304           ./perf probe --target-ns <target pid> -x /lib64/libc.so.6 malloc
305
306       Add a USDT probe to a target process running in a different mount
307       namespace
308
309           ./perf probe --target-ns <target pid> -x /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.121-0.b13.el7_3.x86_64/jre/lib/amd64/server/libjvm.so %sdt_hotspot:thread__sleep__end
310
311       Add a probe on specific versioned symbol by backslash escape
312
313           ./perf probe -x /lib64/libc-2.25.so 'malloc_get_state\@GLIBC_2.2.5'
314
315       Add a probe in a source file using special characters by backslash
316       escape
317
318           ./perf probe -x /opt/test/a.out 'foo\+bar.c:4'
319

PERMISSIONS AND SYSCTL

321       Since perf probe depends on ftrace (tracefs) and kallsyms
322       (/proc/kallsyms), you have to care about the permission and some sysctl
323       knobs.
324
325       •   Since tracefs and kallsyms requires root or privileged user to
326           access it, the following perf probe commands also require it;
327           --add, --del, --list (except for --cache option)
328
329       •   The system admin can remount the tracefs with 755 (sudo mount -o
330           remount,mode=755 /sys/kernel/tracing/) to allow unprivileged user
331           to run the perf probe --list command.
332
333       •   /proc/sys/kernel/kptr_restrict = 2 (restrict all users) also
334           prevents perf probe to retrieve the important information from
335           kallsyms. You also need to set to 1 (restrict non CAP_SYSLOG users)
336           for the above commands. Since the user-space probe doesn’t need to
337           access kallsyms, this is only for probing the kernel function
338           (kprobes).
339
340       •   Since the perf probe commands read the vmlinux (for kernel) and/or
341           the debuginfo file (including user-space application), you need to
342           ensure that you can read those files.
343

SEE ALSO

345       perf-trace(1), perf-record(1), perf-buildid-cache(1)
346
347
348
349perf                              06/14/2022                     PERF-PROBE(1)
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