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

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Date:	Mon, 9 Mar 2009 09:44:35 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
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 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 ;-)

>  
> @@ -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


> +	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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