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    SubjectRe: [PATCH perf/core 1/4] perf-probe: Fix to show correct locations for events on modules
    On Tue, 10 Jan 2017 10:18:35 -0300
    Arnaldo Carvalho de Melo <acme@kernel.org> wrote:

    > Em Sat, Jan 07, 2017 at 02:25:09PM +0900, Masami Hiramatsu escreveu:
    > > Fix to show correct locations for events on modules by
    > > relocating given address. Currently the relocation is
    > > done when we failed to find the address in debuginfo,
    > > but for modules it always makes a mistakes.
    >
    > Try to provide precise instructions on how to reproduce, for instance,
    > here I'm not being able to reproduce:
    >
    > [root@jouet ~]# perf probe -m i915 chv_prepare_pll
    > Added new event:
    > probe:chv_prepare_pll (on chv_prepare_pll in i915)
    >
    > You can now use it in all perf tools, such as:
    >
    > perf record -e probe:chv_prepare_pll -aR sleep 1
    >
    > [root@jouet ~]# perf probe -l
    > probe:chv_prepare_pll (on chv_prepare_pll in i915)
    > probe:e1000_xmit_frame (on e1000_get_link_up_info_80003es2lan:7@intel/e1000e/80003es2lan.c in e1000e)
    > [root@jouet ~]#
    >
    > So it doesn't seem to "always make mistakes", what are the precise
    > conditions to reproduce this problem?

    Hmm, OK, I also found same issue. I'll recheck that...

    Thank you,

    >
    > Running with 'perf probe -vv -m i915 chv_prepare_pll' to get more
    > debugging info:
    >
    > Failed to get build-id from i915.
    > Cache open error: -1
    > Open Debuginfo file: /lib/modules/4.9.0+/kernel/drivers/gpu/drm/i915/i915.ko
    > Try to find probe point from debuginfo.
    > Matched function: chv_prepare_pll [6ce853]
    > found inline addr: 0x883a0
    > Probe point found: chv_prepare_pll+0
    > Found 1 probe_trace_events.
    > Opening /sys/kernel/debug/tracing//kprobe_events write=1
    > Writing event: p:probe/chv_prepare_pll i915:chv_prepare_pll+0
    > Added new event:
    > probe:chv_prepare_pll (on chv_prepare_pll in i915)
    >
    > You can now use it in all perf tools, such as:
    >
    > perf record -e probe:chv_prepare_pll -aR sleep 1
    >
    > [root@jouet ~]#
    >
    > - Arnaldo
    >
    > > E.g. without this fix, events on module seems wrong,
    > > but other cases (kernel and user space) looks good.
    > >
    > > # perf probe -l
    > > probe:SyS_remap_file_pages (on SyS_remap_file_pages@mm/mmap.c)
    > > probe:chv_prepare_pll (on intel_plane_atomic_get_property+16@drm/i915/intel_atomic_plane.c in i915)
    > > probe_perf:alias_lookup (on alias_lookup@util/alias.c in /home/mhiramat/ksrc/linux/tools/perf/perf)
    > >
    > > With this fix, all cases are OK now.
    > >
    > > # perf probe -l
    > > probe:SyS_remap_file_pages (on SyS_remap_file_pages@mm/mmap.c)
    > > probe:chv_prepare_pll (on chv_prepare_pll@gpu/drm/i915/intel_display.c in i915)
    > > probe_perf:alias_lookup (on alias_lookup@util/alias.c in /home/mhiramat/ksrc/linux/tools/perf/perf)
    > >
    > > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
    > > ---
    > > tools/perf/util/probe-finder.c | 10 +++-------
    > > 1 file changed, 3 insertions(+), 7 deletions(-)
    > >
    > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
    > > index df4debe..0278fe1 100644
    > > --- a/tools/perf/util/probe-finder.c
    > > +++ b/tools/perf/util/probe-finder.c
    > > @@ -1543,16 +1543,12 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, unsigned long addr,
    > > Dwarf_Addr _addr = 0, baseaddr = 0;
    > > const char *fname = NULL, *func = NULL, *basefunc = NULL, *tmp;
    > > int baseline = 0, lineno = 0, ret = 0;
    > > - bool reloc = false;
    > >
    > > -retry:
    > > + /* We always need to relocate the address for aranges */
    > > + if (debuginfo__get_text_offset(dbg, &baseaddr) == 0)
    > > + addr += baseaddr;
    > > /* Find cu die */
    > > if (!dwarf_addrdie(dbg->dbg, (Dwarf_Addr)addr, &cudie)) {
    > > - if (!reloc && debuginfo__get_text_offset(dbg, &baseaddr) == 0) {
    > > - addr += baseaddr;
    > > - reloc = true;
    > > - goto retry;
    > > - }
    > > pr_warning("Failed to find debug information for address %lx\n",
    > > addr);
    > > ret = -EINVAL;


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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