linux-kernel - Re: [RFC][PATCH 1/2] tracing/ftrace: syscall tracing infrastructure

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Date:	Mon, 9 Mar 2009 21:42:56 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Jiaying Zhang <jiayingz@...gle.com>,
	Martin Bligh <mbligh@...gle.com>
Subject: Re: [RFC][PATCH 1/2] tracing/ftrace: syscall tracing infrastructure

On Mon, Mar 09, 2009 at 09:44:35AM -0400, Steven Rostedt wrote:
> 
> On Sat, 7 Mar 2009, Frederic Weisbecker wrote:
> >  
> >  libftrace-y := ftrace.o
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index cc94f86..5152be3 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -242,6 +242,12 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
> >  unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
> >  	TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO;
> >  
> > +
> > +struct trace_array *__get_global_trace(void)
> > +{
> > +	return &global_trace;
> > +}
> > +
> 
> 
> Don't do that. It's opening up a can of worms ;-)



That's right. I just wanted to have the insertion done in the dedicated file.

 
> >  
> > @@ -568,6 +587,7 @@ extern int trace_selftest_startup_branch(struct tracer *trace,
> >  #endif /* CONFIG_FTRACE_STARTUP_TEST */
> >  
> >  extern void *head_page(struct trace_array_cpu *data);
> > +extern struct trace_array *__get_global_trace(void);
> 
> Remove that too.
> 
> > +void ftrace_syscall_enter(struct pt_regs *regs)
> > +{
> > +	struct trace_array *tr = __get_global_trace();
> 
> Don't do that.
> 
> > +	struct syscall_trace_enter *entry;
> > +	const struct syscall_trace_entry *sys_data;
> > +	struct ring_buffer_event *event;
> > +	struct trace_array_cpu *data;
> > +	int size;
> > +	int syscall_nr;
> > +	int nr_offset;
> > +	int cpu;
> > +
> > +	syscall_nr = syscall_get_nr(current, regs);
> > +	nr_offset = arch_syscall_trace_nr[syscall_nr];
> > +	if (!nr_offset || nr_offset >= __SYSCALL_TRACE_END)
> > +		return;
> > +
> > +	cpu = raw_smp_processor_id();
> > +	data = tr->data[cpu];
> > +
> > +	if (unlikely(atomic_read(&data->disabled)))
> > +		return;
> > +
> > +	sys_data = &syscall_trace_entries[nr_offset];
> > +	size = sizeof(*entry) + sizeof(unsigned long) * sys_data->nb_args;
> > +
> > +	event = trace_buffer_lock_reserve(tr, TRACE_SYSCALL_ENTER, size, 0, 0);
> 
> Here you want:
> 
> 	trace_current_buffer_lock_reserve(TRACE_SYSCALL_ENTER, size, 0, 0);
> 
> 
> -- Steve


Heh! I didn't know this one! :-)
Thanks!


> 
> > +	if (!event)
> > +		return;
> > +
> > +	entry = ring_buffer_event_data(event);
> > +	entry->nr = nr_offset;
> > +	syscall_get_arguments(current, regs, 0, sys_data->nb_args, entry->args);
> > +
> > +	ring_buffer_unlock_commit(tr->buffer, event);
> > +	trace_wake_up();
> > +}
> > +
> > +void ftrace_syscall_exit(struct pt_regs *regs)
> > +{
> > +	struct trace_array *tr = __get_global_trace();
> > +	struct syscall_trace_exit *entry;
> > +	const struct syscall_trace_entry *sys_data;
> > +	struct ring_buffer_event *event;
> > +	struct trace_array_cpu *data;
> > +	int syscall_nr;
> > +	int nr_offset;
> > +	int cpu;
> > +
> > +	syscall_nr = syscall_get_nr(current, regs);
> > +	nr_offset = arch_syscall_trace_nr[syscall_nr];
> > +	if (!nr_offset || nr_offset >= __SYSCALL_TRACE_END)
> > +		return;
> > +
> > +	cpu = raw_smp_processor_id();
> > +	data = tr->data[cpu];
> > +
> > +	if (unlikely(atomic_read(&data->disabled)))
> > +		return;
> > +
> > +	sys_data = &syscall_trace_entries[nr_offset];
> > +
> > +	event = trace_buffer_lock_reserve(tr, TRACE_SYSCALL_EXIT,
> > +				sizeof(*entry), 0, 0);
> 
> Same here.
> 
> > +	if (!event)
> > +		return;
> > +
> > +	entry = ring_buffer_event_data(event);
> > +	entry->nr = nr_offset;
> > +	entry->ret = syscall_get_return_value(current, regs);
> > +
> > +	ring_buffer_unlock_commit(tr->buffer, event);
> > +	trace_wake_up();
> > +}
> > +
> 
> -- Steve
> 

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