From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>,
He Kuang <hekuang@huawei.com>
Cc: a.p.zijlstra@chello.nl, mingo@redhat.com, namhyung@kernel.org,
wangnan0@huawei.com, linux-kernel@vger.kernel.org
Subject: Re: Re: [PATCH] perf probe: Fix failure to probe events on arm
Date: Tue, 16 Jun 2015 15:05:17 +0900 [thread overview]
Message-ID: <557FBC9D.3070501@hitachi.com> (raw)
In-Reply-To: <20150615144911.GA5845@kernel.org>
On 2015/06/15 23:49, Arnaldo Carvalho de Melo wrote:
> Em Mon, Jun 15, 2015 at 08:06:53AM +0000, He Kuang escreveu:
>> Fix failure to probe events on arm, problem is introduced by commit
>> 5a51fcd1f30c ("perf probe: Skip kernel symbols which is out of
>> .text"). For some architectures, label '_etext' is not in the .text
>> section(in .notes section for arm/arm64). Label out of .text section is
>> not loaded as symbols and we got a zero value when look up its address,
>> which causes all events be wrongly skiped.
>>
>> This patch uses kernel map->end when failed to get the address of
>> '_etext' and fixes the problem.
>
> Masami, can't we always use map->end then? Can you please take a look at
> this patch and ack/nack it?
Yeah, it looks good to me, and we finally will replace "_etext" with it :)
----
void map__fixup_end(struct map *map)
{
struct rb_root *symbols = &map->dso->symbols[map->type];
struct rb_node *nd = rb_last(symbols);
if (nd != NULL) {
struct symbol *sym = rb_entry(nd, struct symbol, rb_node);
map->end = sym->end;
}
}
----
So, the map->end shows the end address of the symbols.
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Thanks!
>
> - Arnaldo
>
>
>> Problem can be reproduced on arm as following:
>>
>> # perf probe --add='generic_perform_write'
>> generic_perform_write+0 is out of .text, skip it.
>> Probe point 'generic_perform_write' not found.
>> Error: Failed to add events. Reason: No such file or directory (Code: -2)
>>
>> After this patch:
>>
>> # perf probe --add='generic_perform_write'
>> Added new event:
>> probe:generic_perform_write (on generic_perform_write)
>>
>> You can now use it in all perf tools, such as:
>>
>> perf record -e probe:generic_perform_write -aR sleep 1
>>
>> Signed-off-by: He Kuang <hekuang@huawei.com>
>> ---
>> tools/perf/util/probe-event.c | 16 +++++++++++++++-
>> 1 file changed, 15 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
>> index daa24a2..ee26961 100644
>> --- a/tools/perf/util/probe-event.c
>> +++ b/tools/perf/util/probe-event.c
>> @@ -575,8 +575,22 @@ static int post_process_probe_trace_events(struct probe_trace_event *tevs,
>> pr_warning("Relocated base symbol is not found!\n");
>> return -EINVAL;
>> }
>> - /* Get the address of _etext for checking non-probable text symbol */
>> + /* Get the address of _etext for checking non-probable text symbol,
>> + for some architectures (e.g. arm, arm64), _etext is out of .text
>> + section and not loaded as symbols, use kernel map->end instead.
>> + */
>> etext_addr = kernel_get_symbol_address_by_name("_etext", false);
>> + if (etext_addr == 0) {
>> + struct map *map;
>> +
>> + map = kernel_get_module_map(NULL);
>> + if (!map) {
>> + pr_err("Failed to get a map for kernel\n");
>> + return -EINVAL;
>> + }
>> +
>> + etext_addr = map->end;
>> + }
>>
>> for (i = 0; i < ntevs; i++) {
>> if (tevs[i].point.address && !tevs[i].point.retprobe) {
>> --
>> 1.8.5.2
> --
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--
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2015-06-16 6:05 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-15 8:06 [PATCH] perf probe: Fix failure to probe events on arm He Kuang
2015-06-15 14:49 ` Arnaldo Carvalho de Melo
2015-06-16 6:05 ` Masami Hiramatsu [this message]
2015-06-16 13:39 ` Arnaldo Carvalho de Melo
2015-06-16 15:26 ` hekuang
2015-06-17 8:52 ` Masami Hiramatsu
2015-06-17 9:43 ` He Kuang
2015-06-17 11:18 ` Masami Hiramatsu
2015-06-18 2:49 ` [PATCH v2] " He Kuang
2015-06-19 21:08 ` Arnaldo Carvalho de Melo
2015-06-23 3:07 ` Masami Hiramatsu
2015-06-23 3:07 ` Masami Hiramatsu
2015-06-25 7:57 ` [tip:perf/core] " tip-bot for He Kuang
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