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 <heku...@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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