Re: [PATCH 6/7] uprobes/perf: Teach trace_uprobe/perf code to use UPROBE_HANDLER_REMOVE

[Srikar Dronamraju <srikar@linux.vnet.ibm.com>]

* Oleg Nesterov <oleg@redhat.com> [2013-02-04 20:03:01]:

> Change uprobe_trace_func() and uprobe_perf_func() to return "int". Change
> Change uprobe_dispatcher() to return "trace_ret | perf_ret" although this
> is not really needed, currently TP_FLAG_TRACE/TP_FLAG_PROFILE are mutually
> exclusive.
> 
> The only functional change is that uprobe_perf_func() checks the filtering
> too and returns UPROBE_HANDLER_REMOVE if nobody wants to trace current.
> 
> Testing:
> 
> 	# perf probe -x /lib/libc.so.6 syscall
> 
> 	# perf record -e probe_libc:syscall -i perl -e 'fork; syscall -1 for 1..10; wait'
> 
> 	# perf report --show-total-period
> 		100.00%            10     perl  libc-2.8.so    [.] syscall
> 
> Before this patch:
> 
> 	# cat /sys/kernel/debug/tracing/uprobe_profile
> 		/lib/libc.so.6 syscall				20
> 
> A child process doesn't have a counter, but still it hits this breakoint
> "copied" by dup_mmap().
> 
> After the patch:
> 
> 	# cat /sys/kernel/debug/tracing/uprobe_profile
> 		/lib/libc.so.6 syscall				11
> 
> The child process hits this int3 only once and does unapply_uprobe().
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> ---
>  kernel/trace/trace_uprobe.c |   21 ++++++++++++++-------
>  1 files changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 5d5a261..1114619 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -483,7 +483,7 @@ static const struct file_operations uprobe_profile_ops = {
>  };
> 
>  /* uprobe handler */
> -static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> +static int uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>  {
>  	struct uprobe_trace_entry_head *entry;
>  	struct ring_buffer_event *event;
> @@ -501,7 +501,7 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
>  	event = trace_current_buffer_lock_reserve(&buffer, call->event.type,
>  						  size, irq_flags, pc);
>  	if (!event)
> -		return;
> +		return 0;
> 
>  	entry = ring_buffer_event_data(event);
>  	entry->ip = instruction_pointer(task_pt_regs(current));
> @@ -511,6 +511,8 @@ static void uprobe_trace_func(struct trace_uprobe *tu, struct pt_regs *regs)
> 
>  	if (!filter_current_check_discard(buffer, call, entry, event))
>  		trace_buffer_unlock_commit(buffer, event, irq_flags, pc);
> +
> +	return 0;
>  }
> 
>  /* Event entry printers */
> @@ -718,7 +720,7 @@ static bool uprobe_perf_filter(struct uprobe_consumer *uc,
>  }
> 
>  /* uprobe profile handler */
> -static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
> +static int uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
>  {
>  	struct ftrace_event_call *call = &tu->call;
>  	struct uprobe_trace_entry_head *entry;
> @@ -727,11 +729,14 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
>  	int size, __size, i;
>  	int rctx;
> 
> +	if (!uprobe_perf_filter(&tu->consumer, 0, current->mm))
> +		return UPROBE_HANDLER_REMOVE;
> +
>  	__size = sizeof(*entry) + tu->size;
>  	size = ALIGN(__size + sizeof(u32), sizeof(u64));
>  	size -= sizeof(u32);
>  	if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE, "profile buffer not large enough"))
> -		return;
> +		return 0;
> 
>  	preempt_disable();
> 
> @@ -749,6 +754,7 @@ static void uprobe_perf_func(struct trace_uprobe *tu, struct pt_regs *regs)
> 
>   out:
>  	preempt_enable();
> +	return 0;
>  }
>  #endif	/* CONFIG_PERF_EVENTS */
> 
> @@ -789,18 +795,19 @@ int trace_uprobe_register(struct ftrace_event_call *event, enum trace_reg type,
>  static int uprobe_dispatcher(struct uprobe_consumer *con, struct pt_regs *regs)
>  {
>  	struct trace_uprobe *tu;
> +	int ret = 0;
> 
>  	tu = container_of(con, struct trace_uprobe, consumer);
>  	tu->nhit++;
> 
>  	if (tu->flags & TP_FLAG_TRACE)
> -		uprobe_trace_func(tu, regs);
> +		ret |= uprobe_trace_func(tu, regs);
> 
>  #ifdef CONFIG_PERF_EVENTS
>  	if (tu->flags & TP_FLAG_PROFILE)
> -		uprobe_perf_func(tu, regs);
> +		ret |= uprobe_perf_func(tu, regs);
>  #endif
> -	return 0;
> +	return ret;
>  }
> 
>  static struct trace_event_functions uprobe_funcs = {
> -- 
> 1.5.5.1
> 

-- 
Thanks and Regards
Srikar Dronamraju