linux/tools/perf
Milian Wolff 2ddfd31afc perf report: Ensure the perf DSO mapping matches what libdw sees
[ Upstream commit 2538b9e245 ]

In some situations the libdw unwinder stopped working properly.  I.e.
with libunwind we see:

~~~~~
heaptrack_gui  2228 135073.400112:     641314 cycles:
	            e8ed _dl_fixup (/usr/lib/ld-2.25.so)
	           15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so)
	           ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0)
	           608f3 _GLOBAL__sub_I_kdynamicjobtracker.cpp (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0)
	            f199 call_init.part.0 (/usr/lib/ld-2.25.so)
	            f2a5 _dl_init (/usr/lib/ld-2.25.so)
	             db9 _dl_start_user (/usr/lib/ld-2.25.so)
~~~~~

But with libdw and without this patch this sample is not properly
unwound:

~~~~~
heaptrack_gui  2228 135073.400112:     641314 cycles:
	            e8ed _dl_fixup (/usr/lib/ld-2.25.so)
	           15f06 _dl_runtime_resolve_sse_vex (/usr/lib/ld-2.25.so)
	           ed94c KDynamicJobTracker::KDynamicJobTracker (/home/milian/projects/compiled/kf5/lib64/libKF5KIOWidgets.so.5.35.0)
~~~~~

Debug output showed me that libdw found a module for the last frame
address, but it thinks it belongs to /usr/lib/ld-2.25.so. This patch
double-checks what libdw sees and what perf knows. If the mappings
mismatch, we now report the elf known to perf. This fixes the situation
above, and the libdw unwinder produces the same stack as libunwind.

Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/20170602143753.16907-1-milian.wolff@kdab.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-04-13 19:50:18 +02:00
..
arch
bench perf bench numa: Fixup discontiguous/sparse numa nodes 2018-02-25 11:03:39 +01:00
config
Documentation
python
scripts
tests perf tests kmod-path: Don't fail if compressed modules aren't supported 2018-03-24 10:58:46 +01:00
trace/strace/groups
ui
util perf report: Ensure the perf DSO mapping matches what libdw sees 2018-04-13 19:50:18 +02:00
.gitignore
Build
builtin-annotate.c
builtin-bench.c
builtin-buildid-cache.c
builtin-buildid-list.c
builtin-data.c
builtin-diff.c
builtin-evlist.c
builtin-help.c
builtin-inject.c
builtin-kmem.c
builtin-kvm.c
builtin-list.c
builtin-lock.c
builtin-mem.c
builtin-probe.c perf probe: Return errno when not hitting any event 2018-03-22 09:23:20 +01:00
builtin-record.c
builtin-report.c
builtin-sched.c
builtin-script.c
builtin-stat.c
builtin-timechart.c
builtin-top.c perf top: Fix window dimensions change handling 2018-02-25 11:03:39 +01:00
builtin-trace.c perf trace: Add mmap alias for s390 2018-04-13 19:50:16 +02:00
builtin.h
command-list.txt
CREDITS
design.txt
Makefile
Makefile.perf
MANIFEST
perf-archive.sh
perf-completion.sh
perf-read-vdso.c
perf-sys.h
perf-with-kcore.sh
perf.c
perf.h