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From:   Steve MacLean <Steve.MacLean@microsoft.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>
CC:     Eric Saint-Etienne <eric.saint.etienne@oracle.com>,
        John Keeping <john@metanate.com>,
        Andi Kleen <ak@linux.intel.com>,
        Song Liu <songliubraving@fb.com>,
        Davidlohr Bueso <dave@stgolabs.net>,
        Leo Yan <leo.yan@linaro.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Brian Robbins <brianrob@microsoft.com>,
        Tom McDonald <Thomas.McDonald@microsoft.com>,
        John Salem <josalem@microsoft.com>,
        Stephane Eranian <eranian@google.com>
Subject: [PATCH 1/4] perf map: fix overlapped map handling
Thread-Topic: [PATCH 1/4] perf map: fix overlapped map handling
Thread-Index: AdV1nTZ8lfM9Cf56S6GO5+sKq8wUvw==
Date:   Sat, 28 Sep 2019 01:39:00 +0000
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Whenever an mmap/mmap2 event occurs, the map tree must be updated to add a =
new
entry. If a new map overlaps a previous map, the overlapped section of the
previous map is effectively unmapped, but the non-overlapping sections are
still valid.

maps__fixup_overlappings() is responsible for creating any new map entries =
from
the previously overlapped map. It optionally creates a before and an after =
map.

When creating the after map the existing code failed to adjust the map.pgof=
f.
This meant the new after map would incorrectly calculate the file offset
for the ip. This results in incorrect symbol name resolution for any ip in =
the
after region.

Make maps__fixup_overlappings() correctly populate map.pgoff.

Add an assert that new mapping matches old mapping at the beginning of
the after map.

Committer-testing:

Validated correct parsing of libcoreclr.so symbols from .NET Core 3.0 previ=
ew9
(which didn't strip symbols).

Preparation:

~/dotnet3.0-preview9/dotnet new webapi -o perfSymbol
cd perfSymbol
~/dotnet3.0-preview9/dotnet publish
perf record ~/dotnet3.0-preview9/dotnet \
    bin/Debug/netcoreapp3.0/publish/perfSymbol.dll
^C

Before:

perf script --show-mmap-events 2>&1 | grep -e MMAP -e unknown |\
   grep libcoreclr.so | head -n 4
      dotnet  1907 373352.698780: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615726000(0x768000) @ 0 08:02 5510620 765057155]: \
          r-xp .../3.0.0-preview9-19423-09/libcoreclr.so
      dotnet  1907 373352.701091: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615974000(0x1000) @ 0x24e000 08:02 5510620 765057155]: \
          rwxp .../3.0.0-preview9-19423-09/libcoreclr.so
      dotnet  1907 373352.701241: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615c42000(0x1000) @ 0x51c000 08:02 5510620 765057155]: \
          rwxp .../3.0.0-preview9-19423-09/libcoreclr.so
      dotnet  1907 373352.705249:     250000 cpu-clock: \
           7fe6159a1f99 [unknown] \
           (.../3.0.0-preview9-19423-09/libcoreclr.so)

After:

perf script --show-mmap-events 2>&1 | grep -e MMAP -e unknown |\
   grep libcoreclr.so | head -n 4
      dotnet  1907 373352.698780: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615726000(0x768000) @ 0 08:02 5510620 765057155]: \
          r-xp .../3.0.0-preview9-19423-09/libcoreclr.so
      dotnet  1907 373352.701091: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615974000(0x1000) @ 0x24e000 08:02 5510620 765057155]: \
          rwxp .../3.0.0-preview9-19423-09/libcoreclr.so
      dotnet  1907 373352.701241: PERF_RECORD_MMAP2 1907/1907: \
          [0x7fe615c42000(0x1000) @ 0x51c000 08:02 5510620 765057155]: \
          rwxp .../3.0.0-preview9-19423-09/libcoreclr.so

All the [unknown] symbols were resolved.

Tested-by: Brian Robbins <brianrob@microsoft.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Steve MacLean <Steve.MacLean@Microsoft.com>
---
 tools/perf/util/map.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 5b83ed1..eec9b28 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include "symbol.h"
+#include <assert.h>
 #include <errno.h>
 #include <inttypes.h>
 #include <limits.h>
@@ -850,6 +851,8 @@ static int maps__fixup_overlappings(struct maps *maps, =
struct map *map, FILE *fp
 			}
=20
 			after->start =3D map->end;
+			after->pgoff +=3D map->end - pos->start;
+			assert(pos->map_ip(pos, map->end) =3D=3D after->map_ip(after, map->end)=
);
 			__map_groups__insert(pos->groups, after);
 			if (verbose >=3D 2 && !use_browser)
 				map__fprintf(after, fp);
--=20
2.7.4