linux-kernel - [PATCH] perf dso: Fix dso comparison

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Date:   Tue, 24 Mar 2020 09:54:24 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     acme@...nel.org, jolsa@...hat.com
Cc:     linux-kernel@...r.kernel.org, namhyung@...nel.org,
        mark.rutland@....com, naveen.n.rao@...ux.vnet.ibm.com,
        ravi.bangoria@...ux.ibm.com
Subject: [PATCH] perf dso: Fix dso comparison

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 0e3149f86b99 ("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.

Reported-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Fixes: 0e3149f86b99 ("perf dso: Move dso_id from 'struct map' to 'struct dso'")
Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
---
 tools/perf/util/dsos.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/dsos.c b/tools/perf/util/dsos.c
index 591707c69c39..5c5bfa2538a9 100644
--- a/tools/perf/util/dsos.c
+++ b/tools/perf/util/dsos.c
@@ -26,13 +26,29 @@ static int __dso_id__cmp(struct dso_id *a, struct dso_id *b)
 	return 0;
 }
 
+static bool is_empty_dso_id(struct dso_id *id)
+{
+	if (!id)
+		return true;
+
+	return !id->maj && !id->min && !id->ino && !id->ino_generation;
+}
+
+static void inject_dso_id(struct dso *dso, struct dso_id *id)
+{
+	dso->id.maj = id->maj;
+	dso->id.min = id->min;
+	dso->id.ino = id->ino;
+	dso->id.ino_generation = id->ino_generation;
+}
+
 static int dso_id__cmp(struct dso_id *a, struct dso_id *b)
 {
 	/*
 	 * The second is always dso->id, so zeroes if not set, assume passing
 	 * NULL for a means a zeroed id
 	 */
-	if (a == NULL)
+	if (is_empty_dso_id(a) || is_empty_dso_id(b))
 		return 0;
 
 	return __dso_id__cmp(a, b);
@@ -249,6 +265,10 @@ struct dso *__dsos__addnew(struct dsos *dsos, const char *name)
 static struct dso *__dsos__findnew_id(struct dsos *dsos, const char *name, struct dso_id *id)
 {
 	struct dso *dso = __dsos__find_id(dsos, name, id, false);
+
+	if (dso && is_empty_dso_id(&dso->id) && !is_empty_dso_id(id))
+		inject_dso_id(dso, id);
+
 	return dso ? dso : __dsos__addnew_id(dsos, name, id);
 }
 
-- 
2.24.1