1perf-probe(1) 2============= 3 4NAME 5---- 6perf-probe - Define new dynamic tracepoints 7 8SYNOPSIS 9-------- 10[verse] 11'perf probe' [options] --add='PROBE' [...] 12or 13'perf probe' [options] PROBE 14or 15'perf probe' [options] --del='[GROUP:]EVENT' [...] 16or 17'perf probe' --list[=[GROUP:]EVENT] 18or 19'perf probe' [options] --line='LINE' 20or 21'perf probe' [options] --vars='PROBEPOINT' 22or 23'perf probe' [options] --funcs 24or 25'perf probe' [options] --definition='PROBE' [...] 26 27DESCRIPTION 28----------- 29This command defines dynamic tracepoint events, by symbol and registers 30without debuginfo, or by C expressions (C line numbers, C function names, 31and C local variables) with debuginfo. 32 33 34OPTIONS 35------- 36-k:: 37--vmlinux=PATH:: 38 Specify vmlinux path which has debuginfo (Dwarf binary). 39 Only when using this with --definition, you can give an offline 40 vmlinux file. 41 42-m:: 43--module=MODNAME|PATH:: 44 Specify module name in which perf-probe searches probe points 45 or lines. If a path of module file is passed, perf-probe 46 treat it as an offline module (this means you can add a probe on 47 a module which has not been loaded yet). 48 49-s:: 50--source=PATH:: 51 Specify path to kernel source. 52 53-v:: 54--verbose:: 55 Be more verbose (show parsed arguments, etc). 56 Can not use with -q. 57 58-q:: 59--quiet:: 60 Do not show any warnings or messages. 61 Can not use with -v. 62 63-a:: 64--add=:: 65 Define a probe event (see PROBE SYNTAX for detail). 66 67-d:: 68--del=:: 69 Delete probe events. This accepts glob wildcards('*', '?') and character 70 classes(e.g. [a-z], [!A-Z]). 71 72-l:: 73--list[=[GROUP:]EVENT]:: 74 List up current probe events. This can also accept filtering patterns of 75 event names. 76 When this is used with --cache, perf shows all cached probes instead of 77 the live probes. 78 79-L:: 80--line=:: 81 Show source code lines which can be probed. This needs an argument 82 which specifies a range of the source code. (see LINE SYNTAX for detail) 83 84-V:: 85--vars=:: 86 Show available local variables at given probe point. The argument 87 syntax is same as PROBE SYNTAX, but NO ARGs. 88 89--externs:: 90 (Only for --vars) Show external defined variables in addition to local 91 variables. 92 93--no-inlines:: 94 (Only for --add) Search only for non-inlined functions. The functions 95 which do not have instances are ignored. 96 97-F:: 98--funcs[=FILTER]:: 99 Show available functions in given module or kernel. With -x/--exec, 100 can also list functions in a user space executable / shared library. 101 This also can accept a FILTER rule argument. 102 103-D:: 104--definition=:: 105 Show trace-event definition converted from given probe-event instead 106 of write it into tracing/[k,u]probe_events. 107 108--filter=FILTER:: 109 (Only for --vars and --funcs) Set filter. FILTER is a combination of glob 110 pattern, see FILTER PATTERN for detail. 111 Default FILTER is "!__k???tab_* & !__crc_*" for --vars, and "!_*" 112 for --funcs. 113 If several filters are specified, only the last filter is used. 114 115-f:: 116--force:: 117 Forcibly add events with existing name. 118 119-n:: 120--dry-run:: 121 Dry run. With this option, --add and --del doesn't execute actual 122 adding and removal operations. 123 124--cache:: 125 (With --add) Cache the probes. Any events which successfully added 126 are also stored in the cache file. 127 (With --list) Show cached probes. 128 (With --del) Remove cached probes. 129 130--max-probes=NUM:: 131 Set the maximum number of probe points for an event. Default is 128. 132 133--target-ns=PID: 134 Obtain mount namespace information from the target pid. This is 135 used when creating a uprobe for a process that resides in a 136 different mount namespace from the perf(1) utility. 137 138-x:: 139--exec=PATH:: 140 Specify path to the executable or shared library file for user 141 space tracing. Can also be used with --funcs option. 142 143--demangle:: 144 Demangle application symbols. --no-demangle is also available 145 for disabling demangling. 146 147--demangle-kernel:: 148 Demangle kernel symbols. --no-demangle-kernel is also available 149 for disabling kernel demangling. 150 151In absence of -m/-x options, perf probe checks if the first argument after 152the options is an absolute path name. If its an absolute path, perf probe 153uses it as a target module/target user space binary to probe. 154 155PROBE SYNTAX 156------------ 157Probe points are defined by following syntax. 158 159 1) Define event based on function name 160 [[GROUP:]EVENT=]FUNC[@SRC][:RLN|+OFFS|%return|;PTN] [ARG ...] 161 162 2) Define event based on source file with line number 163 [[GROUP:]EVENT=]SRC:ALN [ARG ...] 164 165 3) Define event based on source file with lazy pattern 166 [[GROUP:]EVENT=]SRC;PTN [ARG ...] 167 168 4) Pre-defined SDT events or cached event with name 169 %[sdt_PROVIDER:]SDTEVENT 170 or, 171 sdt_PROVIDER:SDTEVENT 172 173'EVENT' specifies the name of new event, if omitted, it will be set the name of the probed function, and for return probes, a "\_\_return" suffix is automatically added to the function name. You can also specify a group name by 'GROUP', if omitted, set 'probe' is used for kprobe and 'probe_<bin>' is used for uprobe. 174Note that using existing group name can conflict with other events. Especially, using the group name reserved for kernel modules can hide embedded events in the 175modules. 176'FUNC' specifies a probed function name, and it may have one of the following options; '+OFFS' is the offset from function entry address in bytes, ':RLN' is the relative-line number from function entry line, and '%return' means that it probes function return. And ';PTN' means lazy matching pattern (see LAZY MATCHING). Note that ';PTN' must be the end of the probe point definition. In addition, '@SRC' specifies a source file which has that function. 177It is also possible to specify a probe point by the source line number or lazy matching by using 'SRC:ALN' or 'SRC;PTN' syntax, where 'SRC' is the source file path, ':ALN' is the line number and ';PTN' is the lazy matching pattern. 178'ARG' specifies the arguments of this probe point, (see PROBE ARGUMENT). 179'SDTEVENT' and 'PROVIDER' is the pre-defined event name which is defined by user SDT (Statically Defined Tracing) or the pre-cached probes with event name. 180Note that before using the SDT event, the target binary (on which SDT events are defined) must be scanned by linkperf:perf-buildid-cache[1] to make SDT events as cached events. 181 182For details of the SDT, see below. 183https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html 184 185ESCAPED CHARACTER 186----------------- 187 188In the probe syntax, '=', '@', '+', ':' and ';' are treated as a special character. You can use a backslash ('\') to escape the special characters. 189This is useful if you need to probe on a specific versioned symbols, like @GLIBC_... suffixes, or also you need to specify a source file which includes the special characters. 190Note that usually single backslash is consumed by shell, so you might need to pass double backslash (\\) or wrapping with single quotes (\'AAA\@BBB'). 191See EXAMPLES how it is used. 192 193PROBE ARGUMENT 194-------------- 195Each probe argument follows below syntax. 196 197 [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE][@user] 198 199'NAME' specifies the name of this argument (optional). You can use the name of local variable, local data structure member (e.g. var->field, var.field2), local array with fixed index (e.g. array[1], var->array[0], var->pointer[2]), or kprobe-tracer argument format (e.g. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.) 200'$vars' and '$params' special arguments are also available for NAME, '$vars' is expanded to the local variables (including function parameters) which can access at given probe point. '$params' is expanded to only the function parameters. 201'TYPE' casts the type of this argument (optional). If omitted, perf probe automatically set the type based on debuginfo (*). Currently, basic types (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal integers (x/x8/x16/x32/x64), signedness casting (u/s), "string" and bitfield are supported. (see TYPES for detail) 202On x86 systems %REG is always the short form of the register: for example %AX. %RAX or %EAX is not valid. 203"@user" is a special attribute which means the LOCALVAR will be treated as a user-space memory. This is only valid for kprobe event. 204 205TYPES 206----- 207Basic types (u8/u16/u32/u64/s8/s16/s32/s64) and hexadecimal integers (x8/x16/x32/x64) are integer types. Prefix 's' and 'u' means those types are signed and unsigned respectively, and 'x' means that is shown in hexadecimal format. Traced arguments are shown in decimal (sNN/uNN) or hex (xNN). You can also use 's' or 'u' to specify only signedness and leave its size auto-detected by perf probe. Moreover, you can use 'x' to explicitly specify to be shown in hexadecimal (the size is also auto-detected). 208String type is a special type, which fetches a "null-terminated" string from kernel space. This means it will fail and store NULL if the string container has been paged out. You can specify 'string' type only for the local variable or structure member which is an array of or a pointer to 'char' or 'unsigned char' type. 209Bitfield is another special type, which takes 3 parameters, bit-width, bit-offset, and container-size (usually 32). The syntax is; 210 211 b<bit-width>@<bit-offset>/<container-size> 212 213LINE SYNTAX 214----------- 215Line range is described by following syntax. 216 217 "FUNC[@SRC][:RLN[+NUM|-RLN2]]|SRC[:ALN[+NUM|-ALN2]]" 218 219FUNC specifies the function name of showing lines. 'RLN' is the start line 220number from function entry line, and 'RLN2' is the end line number. As same as 221probe syntax, 'SRC' means the source file path, 'ALN' is start line number, 222and 'ALN2' is end line number in the file. It is also possible to specify how 223many lines to show by using 'NUM'. Moreover, 'FUNC@SRC' combination is good 224for searching a specific function when several functions share same name. 225So, "source.c:100-120" shows lines between 100th to 120th in source.c file. And "func:10+20" shows 20 lines from 10th line of func function. 226 227LAZY MATCHING 228------------- 229The lazy line matching is similar to glob matching but ignoring spaces in both of pattern and target. So this accepts wildcards('*', '?') and character classes(e.g. [a-z], [!A-Z]). 230 231e.g. 232 'a=*' can matches 'a=b', 'a = b', 'a == b' and so on. 233 234This provides some sort of flexibility and robustness to probe point definitions against minor code changes. For example, actual 10th line of schedule() can be moved easily by modifying schedule(), but the same line matching 'rq=cpu_rq*' may still exist in the function.) 235 236FILTER PATTERN 237-------------- 238The filter pattern is a glob matching pattern(s) to filter variables. 239In addition, you can use "!" for specifying filter-out rule. You also can give several rules combined with "&" or "|", and fold those rules as one rule by using "(" ")". 240 241e.g. 242 With --filter "foo* | bar*", perf probe -V shows variables which start with "foo" or "bar". 243 With --filter "!foo* & *bar", perf probe -V shows variables which don't start with "foo" and end with "bar", like "fizzbar". But "foobar" is filtered out. 244 245EXAMPLES 246-------- 247Display which lines in schedule() can be probed: 248 249 ./perf probe --line schedule 250 251Add a probe on schedule() function 12th line with recording cpu local variable: 252 253 ./perf probe schedule:12 cpu 254 or 255 ./perf probe --add='schedule:12 cpu' 256 257Add one or more probes which has the name start with "schedule". 258 259 ./perf probe schedule* 260 or 261 ./perf probe --add='schedule*' 262 263Add probes on lines in schedule() function which calls update_rq_clock(). 264 265 ./perf probe 'schedule;update_rq_clock*' 266 or 267 ./perf probe --add='schedule;update_rq_clock*' 268 269Delete all probes on schedule(). 270 271 ./perf probe --del='schedule*' 272 273Add probes at zfree() function on /bin/zsh 274 275 ./perf probe -x /bin/zsh zfree or ./perf probe /bin/zsh zfree 276 277Add probes at malloc() function on libc 278 279 ./perf probe -x /lib/libc.so.6 malloc or ./perf probe /lib/libc.so.6 malloc 280 281Add a uprobe to a target process running in a different mount namespace 282 283 ./perf probe --target-ns <target pid> -x /lib64/libc.so.6 malloc 284 285Add a USDT probe to a target process running in a different mount namespace 286 287 ./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 288 289Add a probe on specific versioned symbol by backslash escape 290 291 ./perf probe -x /lib64/libc-2.25.so 'malloc_get_state\@GLIBC_2.2.5' 292 293Add a probe in a source file using special characters by backslash escape 294 295 ./perf probe -x /opt/test/a.out 'foo\+bar.c:4' 296 297 298PERMISSIONS AND SYSCTL 299---------------------- 300Since perf probe depends on ftrace (tracefs) and kallsyms (/proc/kallsyms), you have to care about the permission and some sysctl knobs. 301 302 - Since tracefs and kallsyms requires root or privileged user to access it, the following perf probe commands also require it; --add, --del, --list (except for --cache option) 303 304 - The system admin can remount the tracefs with 755 (`sudo mount -o remount,mode=755 /sys/kernel/tracing/`) to allow unprivileged user to run the perf probe --list command. 305 306 - /proc/sys/kernel/kptr_restrict = 2 (restrict all users) also prevents perf probe to retrieve the important information from kallsyms. You also need to set to 1 (restrict non CAP_SYSLOG users) for the above commands. Since the user-space probe doesn't need to access kallsyms, this is only for probing the kernel function (kprobes). 307 308 - Since the perf probe commands read the vmlinux (for kernel) and/or the debuginfo file (including user-space application), you need to ensure that you can read those files. 309 310 311SEE ALSO 312-------- 313linkperf:perf-trace[1], linkperf:perf-record[1], linkperf:perf-buildid-cache[1] 314