Messages in this thread Patch in this message | | | Subject | Re: [PATCH] perf probe: Fix failure to probe events on arm | From | hekuang <> | Date | Tue, 16 Jun 2015 23:26:27 +0800 |
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hi, Arnaldo
On 06/15/2015 10:49 PM, 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? > > - Arnaldo
I think _etext is more accurate than kernel map->end, because __map_groups__fixup_end() is called at the end of dso__load_sym(), which fixes map->end to next_map->start.
Comparative result as this: etext_addr=ffffffff819a1b85, map->end=ffffffff81ff1000.
So if possible, we should use _etext.
Thanks. > >> 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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