diff options
Diffstat (limited to 'tools/perf/Documentation/perf-probe.txt')
| -rw-r--r-- | tools/perf/Documentation/perf-probe.txt | 58 |
1 files changed, 51 insertions, 7 deletions
diff --git a/tools/perf/Documentation/perf-probe.txt b/tools/perf/Documentation/perf-probe.txt index 165c2b1d4317..5c43a6edc0e5 100644 --- a/tools/perf/Documentation/perf-probe.txt +++ b/tools/perf/Documentation/perf-probe.txt @@ -57,7 +57,7 @@ OPTIONS -q:: --quiet:: - Be quiet (do not show any messages including errors). + Do not show any warnings or messages. Can not use with -v. -a:: @@ -130,6 +130,11 @@ OPTIONS --max-probes=NUM:: Set the maximum number of probe points for an event. Default is 128. +--target-ns=PID: + Obtain mount namespace information from the target pid. This is + used when creating a uprobe for a process that resides in a + different mount namespace from the perf(1) utility. + -x:: --exec=PATH:: Specify path to the executable or shared library file for user @@ -165,7 +170,7 @@ Probe points are defined by following syntax. or, sdt_PROVIDER:SDTEVENT -'EVENT' specifies the name of new event, if omitted, it will be set the name of the probed function. You can also specify a group name by 'GROUP', if omitted, set 'probe' is used for kprobe and 'probe_<bin>' is used for uprobe. +'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. Note 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 modules. '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. @@ -177,16 +182,25 @@ Note that before using the SDT event, the target binary (on which SDT events are For details of the SDT, see below. https://sourceware.org/gdb/onlinedocs/gdb/Static-Probe-Points.html +ESCAPED CHARACTER +----------------- + +In the probe syntax, '=', '@', '+', ':' and ';' are treated as a special character. You can use a backslash ('\') to escape the special characters. +This 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. +Note that usually single backslash is consumed by shell, so you might need to pass double backslash (\\) or wrapping with single quotes (\'AAA\@BBB'). +See EXAMPLES how it is used. + PROBE ARGUMENT -------------- Each probe argument follows below syntax. - [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE] + [NAME=]LOCALVAR|$retval|%REG|@SYMBOL[:TYPE][@user] '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. $retval, %ax, etc). Note that the name of this argument will be set as the last member name if you specify a local data structure member (e.g. field2 for 'var->field1.field2'.) '$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. '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) On x86 systems %REG is always the short form of the register: for example %AX. %RAX or %EAX is not valid. +"@user" is a special attribute which means the LOCALVAR will be treated as a user-space memory. This is only valid for kprobe event. TYPES ----- @@ -208,11 +222,11 @@ probe syntax, 'SRC' means the source file path, 'ALN' is start line number, and 'ALN2' is end line number in the file. It is also possible to specify how many lines to show by using 'NUM'. Moreover, 'FUNC@SRC' combination is good for searching a specific function when several functions share same name. -So, "source.c:100-120" shows lines between 100th to l20th in source.c file. And "func:10+20" shows 20 lines from 10th line of func function. +So, "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. LAZY MATCHING ------------- - The 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]). +The 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]). e.g. 'a=*' can matches 'a=b', 'a = b', 'a == b' and so on. @@ -221,8 +235,8 @@ This provides some sort of flexibility and robustness to probe point definitions FILTER PATTERN -------------- - The filter pattern is a glob matching pattern(s) to filter variables. - In 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 "(" ")". +The filter pattern is a glob matching pattern(s) to filter variables. +In 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 "(" ")". e.g. With --filter "foo* | bar*", perf probe -V shows variables which start with "foo" or "bar". @@ -264,6 +278,36 @@ Add probes at malloc() function on libc ./perf probe -x /lib/libc.so.6 malloc or ./perf probe /lib/libc.so.6 malloc +Add a uprobe to a target process running in a different mount namespace + + ./perf probe --target-ns <target pid> -x /lib64/libc.so.6 malloc + +Add a USDT probe to a target process running in a different mount namespace + + ./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 + +Add a probe on specific versioned symbol by backslash escape + + ./perf probe -x /lib64/libc-2.25.so 'malloc_get_state\@GLIBC_2.2.5' + +Add a probe in a source file using special characters by backslash escape + + ./perf probe -x /opt/test/a.out 'foo\+bar.c:4' + + +PERMISSIONS AND SYSCTL +---------------------- +Since perf probe depends on ftrace (tracefs) and kallsyms (/proc/kallsyms), you have to care about the permission and some sysctl knobs. + + - 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) + + - 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. + + - /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). + + - 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. + + SEE ALSO -------- linkperf:perf-trace[1], linkperf:perf-record[1], linkperf:perf-buildid-cache[1] |