| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Tue, 10 Mar 2009 09:45:56 -0400 (EDT)
From: Steven Rostedt <rostedt@...dmis.org>
To: Ingo Molnar <mingo@...e.hu>
cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Theodore Tso <tytso@....edu>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Mathieu Desnoyers <compudj@...stal.dyndns.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
"Martin J. Bligh" <mbligh@...igh.org>,
"Frank Ch. Eigler" <fche@...hat.com>,
Larry Woodman <lwoodman@...hat.com>,
Jason Baron <jbaron@...hat.com>,
Tom Zanussi <tzanussi@...il.com>,
Masami Hiramatsu <mhiramat@...hat.com>,
Christoph Hellwig <hch@...radead.org>,
Jiaying Zhang <jiayingz@...gle.com>,
Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 4/7] tracing: new format for specialized trace points
On Tue, 10 Mar 2009, Ingo Molnar wrote:
>
> * KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> wrote:
>
> > Hi Steven,
> >
> > > TRACE_EVENT(sched_switch,
> > >
> > > TP_PROTO(struct rq *rq, struct task_struct *prev,
> > > struct task_struct *next),
> > >
> > > TP_ARGS(rq, prev, next),
> > >
> > > TP_STRUCT__entry(
> > > __array( char, prev_comm, TASK_COMM_LEN )
> > > __field( pid_t, prev_pid )
> > > __field( int, prev_prio )
> > > __array( char, next_comm, TASK_COMM_LEN )
> > > __field( pid_t, next_pid )
> > > __field( int, next_prio )
> > > ),
> > >
> > > TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
> > > __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
> > > __entry->next_comm, __entry->next_pid, __entry->next_prio),
> > >
> > > TP_fast_assign(
> > > memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
> > > __entry->prev_pid = prev->pid;
> > > __entry->prev_prio = prev->prio;
> > > memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
> > > __entry->next_pid = next->pid;
> > > __entry->next_prio = next->prio;
> > > )
> > > );
> >
> > Could you please write the documentation how to make new
> > tracepont and use various TP_ macro? Some developer (include
> > me) plan to add new tracepoint. but these macro usage is a bit
> > difficult.
>
> Sure, here's a commented/annotated variant:
>
> /*
> * We define a tracepoint, its arguments, its printk format
> * and its 'fast binay record' layout.
> *
> * Firstly, name your tracepoint via TRACE_EVENT(name : the
> * 'subsystem_event' notation is fine.
> *
> * Think about this whole construct as the
> * 'trace_sched_switch() function' from now on.
> */
>
> TRACE_EVENT(sched_switch,
>
> /*
> * A function has a regular function arguments
> * prototype, declare it via TP_PROTO():
> */
> TP_PROTO(struct rq *rq, struct task_struct *prev,
> struct task_struct *next),
>
> /*
> * Define the call signature of the 'function'.
> * (Design sidenote: we use this instead of a
> * TP_PROTO1/TP_PROTO2/TP_PROTO3 ugliness.)
> */
> TP_ARGS(rq, prev, next),
>
> /*
> * Fast binary tracing: define the trace record via
> * TP_STRUCT__entry(). You can think about it like a
> * regular C structure local variable definition.
> *
> * This is how the trace record is structured and will
> * be saved into the ring buffer. These are the fields
> * that will be exposed to user-space in
> * /debug/tracing/events/*/format.
> *
> * The declared 'local variable' is called '__entry'
> */
> TP_STRUCT__entry(
> __array( char, prev_comm, TASK_COMM_LEN )
> __field( pid_t, prev_pid )
> __field( int, prev_prio )
> __array( char, next_comm, TASK_COMM_LEN )
> __field( pid_t, next_pid )
> __field( int, next_prio )
> ),
>
> /*
> * Assign the entry into the trace record, by embedding
> * a full C statement block into TP_fast_assign(). You
> * can refer to the trace record as '__entry' -
> * otherwise you can put arbitrary C code in here.
> *
> * Note: this C code will execute every time a trace event
> * happens, on an active tracepoint.
> */
> TP_fast_assign(
> memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
> __entry->prev_pid = prev->pid;
> __entry->prev_prio = prev->prio;
> memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
> __entry->next_pid = next->pid;
> __entry->next_prio = next->prio;
> )
>
> /*
> * Formatted output of a trace record via TP_printk().
> * This is how the tracepoint will appear under ftrace
> * plugins that make use of this tracepoint.
> *
> * (raw-binary tracing wont actually perform this step.)
> */
> TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
> __entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
> __entry->next_comm, __entry->next_pid, __entry->next_prio),
>
> );
>
> This macro construct is thus used for the regular printk format
> tracing setup, it is used to construct a function pointer based
> tracepoint callback (this is used by programmatic plugins and
> can also by used by generic instrumentation like SystemTap), and
> it is also used to expose a structured trace record in
> /debug/tracing/events/.
Thanks, I'll add the above to include/linux/tracepoint.h as a documented
example.
>
> Steve: i flipped around TP_fast_assign() and TP_printk() in the
> example above because it makes more sense that way. (we first
> assign the record, then we print it out) I suspect we should
> flip it around in the code too.
OK, I'll make that change too.
-- Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists