linux-kernel - RE: [PATCH] perf probe: Fix module probing with shortname

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Date:	Thu, 24 Sep 2015 10:18:50 +0000
From:	平松雅巳 / HIRAMATU，MASAMI 
	<masami.hiramatsu.pt@...achi.com>
To:	"'Arnaldo Carvalho de Melo'" <acme@...nel.org>,
	"Wangnan (F)" <wangnan0@...wei.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lizefan@...wei.com" <lizefan@...wei.com>,
	"pi3orama@....com" <pi3orama@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>
Subject: RE: [PATCH] perf probe: Fix module probing with shortname

From: Arnaldo Carvalho de Melo [mailto:acme@...nel.org]
>Em Wed, Sep 23, 2015 at 01:03:19PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Tue, Sep 22, 2015 at 11:49:02PM -0300, Arnaldo Carvalho de Melo escreveu:
>> > Em Wed, Sep 23, 2015 at 09:14:44AM +0800, Wangnan (F) escreveu:
>> > > On 2015/9/22 21:35, Arnaldo Carvalho de Melo wrote:
>> > > >Em Tue, Sep 22, 2015 at 03:34:32AM +0000, Wang Nan escreveu:
>> > > >>This is caused by a misunderstood of dso->kernel in kernel_get_module_dso()
>> > > >>that, for kernel module, dso->kernel is DSO_TYPE_USER. dso->kernel is DSO_TYPE_KERNEL
>> > > >>iff dso is vmlinux.
>> > > >Kernel modules having DSO_TYPE_USER seems to be the bug, no? I'll try to
>> > > >check that...
>
>> > > I also noticed this problem when I working on commit
>> > > 1f121b03d058dd07199d8924373d3c52a207f63b ("perf tools: Deal with
>> > > kernel module names in '[]' correctly") ;)
>
>> > Thanks for working on this, it is an area that needs cleaning up, too
>> > many ways to say what a dso is, will study your findings and try to come
>> > up with a patch proposal tomorrow.
>> > > So care must be taken.
>>
>> So, yes, there are multiple uses for this dso->kernel thing, we need to
>> look at each one and go on clarifying it so that this gets corrected and
>> sane, but I think we need some helpers to clarify all this, namely:
>>
>> 	Adding DSO_TYPE_KMODULE and DSO_TYPE_GUEST_KMODULE, setting
>> dso->kernel with it when loading host and guest kernel modules and
>> adding:
>>
>> 	bool dso__is_host_kernel(struct dso *dso)
>> 	bool dso__is_host_kmodule(struct dso *dso)
>>
>> 	bool dso__is_guest_kernel(struct dso *dso)
>
>So I tried this, ended up basically using __map__is_kernel(), in several
>places, which I think is right, and I've stashed in my tmp.perf/core
>branch so that you can take a look.
>
>But then I realized that we already have a better way to achieve what is
>needed in that function, see the patch below, fixed things for me:


Hmm, this is a bit hacky, but yes, it looks good to me.
However, I hope to have above solution, for future use.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>

Thanks!

>

>
>diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>index 2b78e8f19b45..7fb0533ab18c 100644
>--- a/tools/perf/util/probe-event.c
>+++ b/tools/perf/util/probe-event.c
>@@ -269,12 +269,13 @@ static int kernel_get_module_dso(const char *module, struct dso **pdso)
> 	int ret = 0;
>
> 	if (module) {
>-		list_for_each_entry(dso, &host_machine->dsos.head, node) {
>-			if (!dso->kernel)
>-				continue;
>-			if (strncmp(dso->short_name + 1, module,
>-				    dso->short_name_len - 2) == 0)
>-				goto found;
>+		char module_name[128];
>+
>+		snprintf(module_name, sizeof(module_name), "[%s]", module);
>+		map = map_groups__find_by_name(&host_machine->kmaps, MAP__FUNCTION, module_name);
>+		if (map) {
>+			dso = map->dso;
>+			goto found;
> 		}
> 		pr_debug("Failed to find module %s.\n", module);
> 		return -ENOENT;
--
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