Em Tue, Jun 16, 2015 at 03:05:17PM +0900, Masami Hiramatsu escreveu:
> 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...@hitachi.com>
I can and will apply it, but the question remains, if this approach is
good then when should we bother looking at "_etext" at all, i.e. why not
just use map->end all the time?
I have not thought this thru, this is just based on this ``its ok to use
map->end if "_etext" is not found'' idea that He proposed and you acked.
- Arnaldo
>
> 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 <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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>
>
> --
> 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...@hitachi.com
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