Messages in this thread | | | Date | Sun, 19 Mar 2023 20:37:48 -0700 | Subject | [PATCH v4 00/22] Reference count checker and related fixes | From | Ian Rogers <> |
| |
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/
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). A summary of the sizes of each patch is:
92e1b65b136b perf map: Add reference count checking 12 files changed, 136 insertions(+), 114 deletions(-) 7fef12ca75a1 perf maps: Add reference count checking. 8 files changed, 64 insertions(+), 56 deletions(-) 1a57842b86fd perf namespaces: Add reference count checking 7 files changed, 83 insertions(+), 62 deletions(-) 6e50b206b364 perf cpumap: Add reference count checking 6 files changed, 81 insertions(+), 71 deletions(-) d64ebe641edd libperf: Add reference count checking macros. 1 file changed, 94 insertions(+) e0c3f6d95483 perf map: Changes to reference counting 11 files changed, 114 insertions(+), 44 deletions(-) d34755aef532 perf maps: Modify maps_by_name to hold a reference to a map 2 files changed, 33 insertions(+), 18 deletions(-) 24c5eb40b0b4 perf test: Add extra diagnostics to maps test 1 file changed, 36 insertions(+), 15 deletions(-) 1f1540178acf perf map: Add accessors for pgoff and reloc 9 files changed, 33 insertions(+), 23 deletions(-) a9f0c85f6269 perf map: Add accessors for prot, priv and flags 6 files changed, 28 insertions(+), 12 deletions(-) ee07e4fbbf8f perf map: Add helper for map_ip and unmap_ip 23 files changed, 80 insertions(+), 65 deletions(-) a2ff37e2d9c1 perf map: Rename map_ip and unmap_ip 6 files changed, 13 insertions(+), 13 deletions(-) 285214010556 perf map: Add accessor for start and end 24 files changed, 114 insertions(+), 103 deletions(-) bcd608c93c81 perf map: Add accessor for dso 48 files changed, 404 insertions(+), 293 deletions(-) d921b7cb8254 perf maps: Add functions to access maps 20 files changed, 175 insertions(+), 111 deletions(-) 3909794aab1c perf maps: Remove rb_node from struct map 16 files changed, 291 insertions(+), 184 deletions(-) c202320ec659 perf map: Move map list node into symbol 2 files changed, 60 insertions(+), 35 deletions(-) 5f0c2abb3f6b perf symbol: Sort names under write lock 1 file changed, 7 insertions(+) 38c930af7ecb perf test: Fix memory leak in symbols 1 file changed, 1 insertion(+) 144f31b33eff perf tests: Add common error route for code-reading 1 file changed, 23 insertions(+), 16 deletions(-) d043380916fb perf bpf_counter: Use public cpumap accessors 1 file changed, 3 insertions(+), 3 deletions(-) 08d8e5dd2277 perf symbol: Avoid memory leak from abi::__cxa_demangle 1 file changed, 2 insertions(+), 3 deletions(-)
The v3 change is available here: https://lore.kernel.org/lkml/20220211103415.2737789-1-irogers@google.com/
Ian Rogers (22): perf symbol: Avoid memory leak from abi::__cxa_demangle perf bpf_counter: Use public cpumap accessors perf tests: Add common error route for code-reading perf test: Fix memory leak in symbols perf symbol: Sort names under write lock 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 | 76 +++-- 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 | 7 +- 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_counter.c | 6 +- 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/demangle-cxx.cpp | 5 +- tools/perf/util/dlfilter.c | 28 +- tools/perf/util/dso.c | 8 +- tools/perf/util/dsos.c | 2 +- tools/perf/util/event.c | 29 +- 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 | 316 +++++++++++------ 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 +- 75 files changed, 1696 insertions(+), 1062 deletions(-) create mode 100644 tools/lib/perf/include/internal/rc_check.h
-- 2.40.0.rc1.284.g88254d51c5-goog
| |