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

平松雅巳 / HIRAMATU，MASAMI
2015-09-25T01:57:10Z

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From: Arnaldo Carvalho de Melo [mailto:acme@kernel.org]
>> >Sent: Thursday, September 24, 2015 10:50 AM
>> >To: Wangnan (F)
>> >Cc: linux-kernel@vger.kernel.org; lizefan@huawei.com; pi3orama@163.com; Namhyung Kim; Jiri Olsa; å¹³æ¾é›…å·³ / HIRAMATUï¼ŒMASAMI
>> >Subject: Re: [PATCH] perf probe: Fix module probing with shortname
>> >
>> >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.
>
>You mean the [] dso->short_name part? But that was already being taken
>into account by the previous, dso list search.

Ah, OK. I didn't know that...

>But yeah, probably we should remove those brackets, anything requiring
>full disambiguation should use the dso->long_name anyway, but I'll
>leave this for later :)

OK, thanks,

>
>> However, I hope to have above solution, for future use.
>
>Right, my work now is to reduce the use of dso->kernel, using
>__map__is_kernel(map), we'll see what is left.
>
>> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>
>Thanks!

Thanks!
>
>> 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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