]> git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/commit - kernel/trace/trace.c
tracing: Add a probe that attaches to trace events
authorTzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Thu, 19 Aug 2021 15:26:06 +0000 (11:26 -0400)
committerSteven Rostedt (VMware) <rostedt@goodmis.org>
Fri, 20 Aug 2021 18:18:40 +0000 (14:18 -0400)
commit7491e2c442781a1860181adb5ab472a52075f393
tree23617684d3162cc63111a7c7128522ba743568fe
parent8e242060c6a4947e8ae7d29794af6a581db08841
tracing: Add a probe that attaches to trace events

A new dynamic event is introduced: event probe. The event is attached
to an existing tracepoint and uses its fields as arguments. The user
can specify custom format string of the new event, select what tracepoint
arguments will be printed and how to print them.
An event probe is created by writing configuration string in
'dynamic_events' ftrace file:
 e[:[SNAME/]ENAME] SYSTEM/EVENT [FETCHARGS] - Set an event probe
 -:SNAME/ENAME - Delete an event probe

Where:
 SNAME - System name, if omitted 'eprobes' is used.
 ENAME - Name of the new event in SNAME, if omitted the SYSTEM_EVENT is used.
 SYSTEM - Name of the system, where the tracepoint is defined, mandatory.
 EVENT - Name of the tracepoint event in SYSTEM, mandatory.
 FETCHARGS - Arguments:
  <name>=$<field>[:TYPE] - Fetch given filed of the tracepoint and print
   it as given TYPE with given name. Supported
   types are:
                    (u8/u16/u32/u64/s8/s16/s32/s64), basic type
                     (x8/x16/x32/x64), hexadecimal types
    "string", "ustring" and bitfield.

Example, attach an event probe on openat system call and print name of the
file that will be opened:
 echo "e:esys/eopen syscalls/sys_enter_openat file=\$filename:string" >> dynamic_events
A new dynamic event is created in events/esys/eopen/ directory. It
can be deleted with:
 echo "-:esys/eopen" >> dynamic_events

Filters, triggers and histograms can be attached to the new event, it can
be matched in synthetic events. There is one limitation - an event probe
can not be attached to kprobe, uprobe or another event probe.

Link: https://lkml.kernel.org/r/20210812145805.2292326-1-tz.stoyanov@gmail.com
Link: https://lkml.kernel.org/r/20210819152825.142428383@goodmis.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Co-developed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
include/linux/trace_events.h
kernel/trace/Makefile
kernel/trace/trace.c
kernel/trace/trace.h
kernel/trace/trace_eprobe.c [new file with mode: 0644]
kernel/trace/trace_events_trigger.c
kernel/trace/trace_kprobe.c
kernel/trace/trace_probe.c
kernel/trace/trace_probe.h