linux-kernel - Re: [RFC] perf probe: Fix module probe issue if no dwarf support

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Message-Id: <20160426062925.9dbfda280af62f077a27e297@kernel.org>
Date:	Tue, 26 Apr 2016 06:29:25 +0900
From:	Masami Hiramatsu <mhiramat@...nel.org>
To:	Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, acme@...nel.org,
	peterz@...radead.org, mingo@...hat.com,
	alexander.shishkin@...ux.intel.com,
	masami.hiramatsu.pt@...achi.com, wangnan0@...wei.com,
	namhyung@...nel.org, srikar@...ux.vnet.ibm.com,
	naveen.n.rao@...ux.vnet.ibm.com
Subject: Re: [RFC] perf probe: Fix module probe issue if no dwarf support

On Mon, 25 Apr 2016 16:08:28 +0530
Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com> wrote:

> Perf is not able to register probe in kernel module when dwarf supprt
> is not there(and so it goes for symtab). Perf passes full path of
> module where only module name is required which is causing the problem.
> This patch fixes this issue.
> 
> Before applying patch:
> 
>   $ dpkg -s libdw-dev
>     dpkg-query: package 'libdw-dev' is not installed ...
> 
>   $ ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
>     Added new event:
>       probe:foo_show (on foo_show in /linux/samples/kobject/kobject-example.ko)
> 
>     You can now use it in all perf tools, such as:
> 
>   perf record -e probe:foo_show -aR sleep 1
> 
>   $ cat /sys/kernel/debug/tracing/kprobe_events
>     p:probe/foo_show /linux/samples/kobject/kobject-example.ko:foo_show
> 
> After applying patch:
> 
>   $ ./perf probe -m /linux/samples/kobject/kobject-example.ko foo_show
>     Added new event:
>       probe:foo_show (on foo_show in kobject_example)
> 
>     You can now use it in all perf tools, such as:
> 
>   perf record -e probe:foo_show -aR sleep 1
> 
>   $ cat /sys/kernel/debug/tracing/kprobe_events
>     p:probe/foo_show kobject_example:foo_show
> 

Looks good to me :)
However, it seems that this patch depends on your previous patch
("perf probe: Fix offline module name missmatch issue")
In that case, could you make these a series of patches?

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thanks,

> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
> ---
>  tools/perf/util/probe-event.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
> index 05d0905..54e6a5a 100644
> --- a/tools/perf/util/probe-event.c
> +++ b/tools/perf/util/probe-event.c
> @@ -2566,6 +2566,7 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  	struct probe_trace_point *tp;
>  	int num_matched_functions;
>  	int ret, i, j, skipped = 0;
> +	char *mod_name;
>  
>  	map = get_target_map(pev->target, pev->uprobes);
>  	if (!map) {
> @@ -2650,9 +2651,19 @@ static int find_probe_trace_events_from_map(struct perf_probe_event *pev,
>  		tp->realname = strdup_or_goto(sym->name, nomem_out);
>  
>  		tp->retprobe = pp->retprobe;
> -		if (pev->target)
> -			tev->point.module = strdup_or_goto(pev->target,
> -							   nomem_out);
> +		if (pev->target) {
> +			if (pev->uprobes) {
> +				tev->point.module = strdup_or_goto(pev->target,
> +								   nomem_out);
> +			} else {
> +				mod_name = find_module_name(pev->target);
> +				tev->point.module =
> +					strdup(mod_name ? mod_name : pev->target);
> +				free(mod_name);
> +				if (!tev->point.module)
> +					goto nomem_out;
> +			}
> +		}
>  		tev->uprobes = pev->uprobes;
>  		tev->nargs = pev->nargs;
>  		if (tev->nargs) {
> -- 
> 2.1.4
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>