Hi Tzvetomir, On Fri, 6 Aug 2021 20:49:28 +0300 "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote: > From: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx> > > The /sys/kernel/debug/tracing/kprobe_events interface is extended with a > new type of user defined dynamic event, that is attached to an existing > tracepoint. The user can specify custom format string of the new event, > select what tracepoint arguments will be printed and how to print them. > > The format is similar to the existing kprobe_events interface: > e:GNAME/ENAME SYSTEM/EVENT [FETCHARGS] - Set an event probe > -e:GNAME/ENAME - Delete an event probe > > Where: > GNAME - Group name, mandatory > ENAME - Name of the new event in GNAME, mandatory > 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 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" >> kprobe_events > A new dynamic event is created in events/esys/eopen/ directory. It > can be deleted with: > echo "-e:esys/eopen" >> kprobe_events Hmm, sorry, I rather like to use synthetic event with trigger action, since this is not a kprobe. Can you change your idea to use trigger action with synthetic event? For example, if we have a "trace" action in the trigger action, echo "eopen char filename[]" >> synthetic_events echo "trace:eopen,filename.ustring" >> events/syscalls/sys_enter_openat/trigger A new action is, trace:SYNTH_EVENT,PARAM(s) [if FILTER] and .ustring/.string modifier for the PARAMS. I think this matches the current dynamic event model, and can extend programmability of the ftrace, and keeps dynamic events simple. Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
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