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SubjectRe: [PATCH] perf machine: Fix load kernel symbol with '-k' option
Hi Mathieu,

On Wed, Mar 07, 2018 at 02:09:24PM -0700, Mathieu Poirier wrote:
> Hi Leo,
>
> On 27 February 2018 at 00:17, Leo Yan <leo.yan@linaro.org> wrote:
> > On Hikey arm64 octa A53 platform, when use command './perf report -v
> > -k vmlinux --stdio' it outputs below error info, and it skips to load
> > kernel symbol and doesn't print symbol for event:
> > Failed to open [kernel.kallsyms]_text, continuing without symbols.
> >
> > The regression is introduced by commit ("8c7f1bb37b29 perf machine: Move
> > kernel mmap name into struct machine"), which changes the logic for
> > machine mmap_name by removing function machine__mmap_name() and always
> > use 'machine->mmap_name'. Comparing difference between
> > machine__mmap_name() and 'machine->mmap_name', the later one includes
> > the string for specified kernel vmlinux string with option '-k' in
> > command, but the old function machine__mmap_name() ignores vmlinux
> > path string. As result, event's mmap file name doesn't match with
> > machine mmap file name anymore and it skips to load kernel symbol from
> > vmlinux file.
> >
> > To resolve this issue, this patch adds extra checking for
> > 'machine->mmap_name', when its start char is not '[' then we can know
> > it includes vmlinux path string specified for option '-k'. For this
> > case it sets 'is_kernel_mmap = true' and run into flow to load kernel
> > symbol from vmlinux.
> >
> > This patch has been verified with two commands: './perf report -v
> > -k vmlinux --stdio' and './perf script -v -F cpu,event,ip,sym,symoff
> > -k vmlinux'.
> >
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > ---
> > tools/perf/util/machine.c | 15 ++++++++++++---
> > 1 file changed, 12 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> > index 12b7427..ffd709d 100644
> > --- a/tools/perf/util/machine.c
> > +++ b/tools/perf/util/machine.c
> > @@ -1299,9 +1299,18 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
> > else
> > kernel_type = DSO_TYPE_GUEST_KERNEL;
> >
> > - is_kernel_mmap = memcmp(event->mmap.filename,
> > - machine->mmap_name,
> > - strlen(machine->mmap_name) - 1) == 0;
> > + /*
> > + * If machine mmap_name doesn't start with char '[', it includes
> > + * the specified kernel vmlinux name with option '-k'. So set
> > + * is_kernel_mmap as true to create machine symbol map.
> > + */
> > + if (machine->mmap_name[0] != '[')
>
> I have tested your patch and it indeed solves the problem but I
> suggest to replace the above with:
>
> if (symbol_conf.vmlinux_name)
>
> That is consistent with the test in function machine__set_mmap_name()
> and doesn't rely on a user specified input to operate properly.

Thanks a lot for suggestion and testing.

Your suggestion does make sense after I go back to read a bit for the
code. Will spin new patch and send out soon for reviewing.

Thanks,
Leo Yan

> > + is_kernel_mmap = true;
> > + else
> > + is_kernel_mmap = memcmp(event->mmap.filename,
> > + machine->mmap_name,
> > + strlen(machine->mmap_name) - 1) == 0;
> > +
> > if (event->mmap.filename[0] == '/' ||
> > (!is_kernel_mmap && event->mmap.filename[0] == '[')) {
> > map = machine__findnew_module_map(machine, event->mmap.start,
> > --
> > 2.7.4
> >

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