[PATCH v5 00/17] Reference count checker and related fixes

Ian Rogers
2023-03-20T21:23:19Z

The perf tool has a class of memory problems where reference counts
are used incorrectly. Memory/address sanitizers and valgrind don't
provide useful ways to debug these problems, you see a memory leak
where the only pertinent information is the original allocation
site. What would be more useful is knowing where a get fails to have a
corresponding put, where there are double puts, etc.

This work was motivated by the roll-back of:
https://lore.kernel.org/linux-perf-users/20211118193714.2293728-1-irogers@google.com/
where fixing a missed put resulted in a use-after-free in a different
context. There was a sense in fixing the issue that a game of
wac-a-mole had been embarked upon in adding missed gets and puts.

The basic approach of the change is to add a level of indirection at
the get and put calls. Get allocates a level of indirection that, if
no corresponding put is called, becomes a memory leak (and associated
stack trace) that leak sanitizer can report. Similarly if two puts are
called for the same get, then a double free can be detected by address
sanitizer. This can also detect the use after put, which should also
yield a segv without a sanitizer.

Adding reference count checking to cpu map was done as a proof of
concept, it yielded little other than a location where the use of get
could be cleaner by using its result. Reference count checking on
nsinfo identified a double free of the indirection layer and the
related threads, thereby identifying a data race as discussed here:
https://lore.kernel.org/linux-perf-users/CAP-5=fWZH20L4kv-BwVtGLwR=Em3AOOT+Q4QGivvQuYn5AsPRg@mail.gmail.com/
Accordingly the dso->lock was extended and use to cover the race.

The v3 version addresses problems in v2, in particular using macros to
avoid #ifdefs. The v3 version applies the reference count checking
approach to two more data structures, maps and map. While maps was
straightforward, struct map showed a problem where reference counted
thing can be on lists and rb-trees that are oblivious to the
reference count. To sanitize this, struct map is changed so that it is
referenced by either a list or rb-tree node and not part of it. This
simplifies the reference count and the patches have caught and fixed a
number of missed or mismatched reference counts relating to struct
map.

The patches are arranged so that API refactors and bug fixes appear
first, then the reference count checker itself appears. This allows
for the refactor and fixes to be applied upstream first, as has
already happened with cpumap.

A wider discussion of the approach is on the mailing list:
https://lore.kernel.org/linux-perf-users/YffqnynWcc5oFkI5@kernel.org/T/#mf25ccd7a2e03de92cec29d36e2999a8ab5ec7f88
Comparing it to a past approach:
https://lore.kernel.org/all/20151209021047.10245.8918.stgit@localhost.localdomain/
and to ref_tracker:
https://lwn.net/Articles/877603/

v5. rebase removing 5 merged changes. Add map_list_node__new to the
1st patch (perf map: Move map list node into symbol) as suggested
by Arnaldo. Remove unnecessary map__puts from patch 12 (perf map:
Changes to reference counting) as suggested by Adrian. A summary
of the sizes of the remaining patches is:
74fd7ffafdd0 perf map: Add reference count checking
12 files changed, 136 insertions(+), 114 deletions(-)
4719196db8d3 perf maps: Add reference count checking.
8 files changed, 64 insertions(+), 56 deletions(-)
03943e7594cf perf namespaces: Add reference count checking
7 files changed, 83 insertions(+), 62 deletions(-)
0bb382cc52d7 perf cpumap: Add reference count checking
6 files changed, 81 insertions(+), 71 deletions(-)
ef39f550c40d libperf: Add reference count checking macros.
1 file changed, 94 insertions(+)
d9ac37c750e0 perf map: Changes to reference counting
11 files changed, 112 insertions(+), 44 deletions(-)
476014bc9b55 perf maps: Modify maps_by_name to hold a reference to a map
2 files changed, 33 insertions(+), 18 deletions(-)
91384676fddd perf test: Add extra diagnostics to maps test
1 file changed, 36 insertions(+), 15 deletions(-)
fdc30434f826 perf map: Add accessors for pgoff and reloc
9 files changed, 33 insertions(+), 23 deletions(-)
368fe015adb2 perf map: Add accessors for prot, priv and flags
6 files changed, 28 insertions(+), 12 deletions(-)
2c6a8169826a perf map: Add helper for map_ip and unmap_ip
23 files changed, 80 insertions(+), 65 deletions(-)
929e59d49f4b perf map: Rename map_ip and unmap_ip
6 files changed, 13 insertions(+), 13 deletions(-)
4a38194aaaf5 perf map: Add accessor for start and end
24 files changed, 114 insertions(+), 103 deletions(-)
02b63e5c415e perf map: Add accessor for dso
48 files changed, 404 insertions(+), 293 deletions(-)
9324af6ccf42 perf maps: Add functions to access maps
20 files changed, 175 insertions(+), 111 deletions(-)
5c590d36a308 perf maps: Remove rb_node from struct map
16 files changed, 291 insertions(+), 184 deletions(-)
af1d142eb777 perf map: Move map list node into symbol
2 files changed, 63 insertions(+), 35 deletions(-)

v4. rebases on to acme's perf-tools-next, fixes more issues with
map/maps and breaks apart the accessor functions to reduce
individual patch sizes. The accessor functions are mechanical
changes where the single biggest one is refactoring use of
map->dso to be map__dso(map).

The v3 change is available here:
https://lore.kernel.org/lkml/20220211103415.2737789-1-irogers@google.com/

Ian Rogers (17):
perf map: Move map list node into symbol
perf maps: Remove rb_node from struct map
perf maps: Add functions to access maps
perf map: Add accessor for dso
perf map: Add accessor for start and end
perf map: Rename map_ip and unmap_ip
perf map: Add helper for map_ip and unmap_ip
perf map: Add accessors for prot, priv and flags
perf map: Add accessors for pgoff and reloc
perf test: Add extra diagnostics to maps test
perf maps: Modify maps_by_name to hold a reference to a map
perf map: Changes to reference counting
libperf: Add reference count checking macros.
perf cpumap: Add reference count checking
perf namespaces: Add reference count checking
perf maps: Add reference count checking.
perf map: Add reference count checking

tools/lib/perf/Makefile | 2 +-
tools/lib/perf/cpumap.c | 94 ++---
tools/lib/perf/include/internal/cpumap.h | 4 +-
tools/lib/perf/include/internal/rc_check.h | 94 +++++
tools/perf/arch/s390/annotate/instructions.c | 4 +-
tools/perf/arch/x86/tests/dwarf-unwind.c | 2 +-
tools/perf/arch/x86/util/event.c | 13 +-
tools/perf/builtin-annotate.c | 11 +-
tools/perf/builtin-buildid-list.c | 4 +-
tools/perf/builtin-inject.c | 12 +-
tools/perf/builtin-kallsyms.c | 6 +-
tools/perf/builtin-kmem.c | 4 +-
tools/perf/builtin-lock.c | 4 +-
tools/perf/builtin-mem.c | 10 +-
tools/perf/builtin-report.c | 26 +-
tools/perf/builtin-script.c | 27 +-
tools/perf/builtin-top.c | 17 +-
tools/perf/builtin-trace.c | 2 +-
.../scripts/python/Perf-Trace-Util/Context.c | 13 +-
tools/perf/tests/code-reading.c | 37 +-
tools/perf/tests/cpumap.c | 4 +-
tools/perf/tests/hists_common.c | 8 +-
tools/perf/tests/hists_cumulate.c | 14 +-
tools/perf/tests/hists_filter.c | 14 +-
tools/perf/tests/hists_link.c | 18 +-
tools/perf/tests/hists_output.c | 12 +-
tools/perf/tests/maps.c | 69 ++--
tools/perf/tests/mmap-thread-lookup.c | 3 +-
tools/perf/tests/symbols.c | 6 +-
tools/perf/tests/thread-maps-share.c | 29 +-
tools/perf/tests/vmlinux-kallsyms.c | 54 +--
tools/perf/ui/browsers/annotate.c | 9 +-
tools/perf/ui/browsers/hists.c | 19 +-
tools/perf/ui/browsers/map.c | 4 +-
tools/perf/util/annotate.c | 40 ++-
tools/perf/util/auxtrace.c | 2 +-
tools/perf/util/block-info.c | 4 +-
tools/perf/util/bpf-event.c | 10 +-
tools/perf/util/bpf_lock_contention.c | 6 +-
tools/perf/util/build-id.c | 2 +-
tools/perf/util/callchain.c | 24 +-
tools/perf/util/cpumap.c | 40 ++-
tools/perf/util/data-convert-json.c | 10 +-
tools/perf/util/db-export.c | 16 +-
tools/perf/util/dlfilter.c | 28 +-
tools/perf/util/dso.c | 8 +-
tools/perf/util/dsos.c | 2 +-
tools/perf/util/event.c | 27 +-
tools/perf/util/evsel_fprintf.c | 4 +-
tools/perf/util/hist.c | 22 +-
tools/perf/util/intel-pt.c | 63 ++--
tools/perf/util/machine.c | 252 ++++++++------
tools/perf/util/map.c | 217 ++++++------
tools/perf/util/map.h | 74 +++-
tools/perf/util/maps.c | 318 ++++++++++-------
tools/perf/util/maps.h | 67 +++-
tools/perf/util/namespaces.c | 132 +++++---
tools/perf/util/namespaces.h | 3 +-
tools/perf/util/pmu.c | 8 +-
tools/perf/util/probe-event.c | 62 ++--
.../util/scripting-engines/trace-event-perl.c | 10 +-
.../scripting-engines/trace-event-python.c | 26 +-
tools/perf/util/sort.c | 67 ++--
tools/perf/util/symbol-elf.c | 41 ++-
tools/perf/util/symbol.c | 320 +++++++++++-------
tools/perf/util/symbol_fprintf.c | 2 +-
tools/perf/util/synthetic-events.c | 34 +-
tools/perf/util/thread-stack.c | 4 +-
tools/perf/util/thread.c | 39 +--
tools/perf/util/unwind-libdw.c | 20 +-
tools/perf/util/unwind-libunwind-local.c | 16 +-
tools/perf/util/unwind-libunwind.c | 33 +-
tools/perf/util/vdso.c | 7 +-
73 files changed, 1665 insertions(+), 1044 deletions(-)
create mode 100644 tools/lib/perf/include/internal/rc_check.h

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2.40.0.rc1.284.g88254d51c5-goog