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    SubjectRe: [PATCH] perf probe: Fix failure to probe events on arm
    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


    > 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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