Perf gets dso details from two different sources. 1st, from builid
headers in perf.data and 2nd from MMAP2 samples. Dso from buildid
header does not have dso_id detail. And dso from MMAP2 samples does
not have buildid information. If detail of the same dso is present
at both the places, filename is common.

Previously, __dsos__findnew_link_by_longname_id() used to compare only
long or short names, but Commit 0e3149f8 ("perf dso: Move dso_id
from 'struct map' to 'struct dso'") also added a dso_id comparison.
Because of that, now perf is creating two different dso objects of the
same file, one from buildid header (with dso_id but without buildid)
and second from MMAP2 sample (with buildid but without dso_id).

This is causing issues with archive, buildid-list etc subcommands. Fix
this by comparing dso_id only when it's present. And incase dso is
present in 'dsos' list without dso_id, inject dso_id detail as well.

Before:

  $ sudo ./perf buildid-list -H
  0000000000000000000000000000000000000000 /usr/bin/ls
  0000000000000000000000000000000000000000 /usr/lib64/ld-2.30.so
  0000000000000000000000000000000000000000 /usr/lib64/libc-2.30.so

  $ ./perf archive
  perf archive: no build-ids found

After:

  $ ./perf buildid-list -H
  b6b1291d0cead046ed0fa5734037fa87a579adee /usr/bin/ls
  641f0c90cfa15779352f12c0ec3c7a2b2b6f41e8 /usr/lib64/ld-2.30.so
  675ace3ca07a0b863df01f461a7b0984c65c8b37 /usr/lib64/libc-2.30.so

  $ ./perf archive
  Now please run:

  $ tar xvf perf.data.tar.bz2 -C ~/.debug

  wherever you need to run 'perf report' on.

Committer notes:

Renamed is_empty_dso_id() to dso_id__empty() and inject_dso_id() to
dso__inject_id() to keep namespacing consistent.

Fixes: 0e3149f8 ("perf dso: Move dso_id from 'struct map' to 'struct dso'")
Reported-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20200324042424.68366-1-ravi.bangoria@linux.ibm.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>