The addr in PERF_RECORD_KSYMBOL events for non-jited bpf progs points to the bpf interpreter, ie. within kernel text section. When processing the unregister event, this causes unexpected removal of vmlinux_map, crashing perf later in cleanup:
# perf record -- timeout --signal=INT 2s /usr/share/bcc/tools/execsnoop PCOMM PID PPID RET ARGS [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.208 MB perf.data (5155 samples) ] perf: tools/include/linux/refcount.h:131: refcount_sub_and_test: Assertion `!(new > val)' failed. Aborted (core dumped) # perf script -D|grep KSYM 0 0xa40 [0x48]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b530 len 0 type 1 flags 0x0 name bpf_prog_f958f6eb72ef5af6 0 0xab0 [0x48]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b530 len 0 type 1 flags 0x0 name bpf_prog_8c42dee26e8cd4c2 0 0xb20 [0x48]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b530 len 0 type 1 flags 0x0 name bpf_prog_f958f6eb72ef5af6 108563691893 0x33d98 [0x58]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b3b0 len 0 type 1 flags 0x0 name bpf_prog_bc5697a410556fc2_syscall__execve 108568518458 0x34098 [0x58]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b3f0 len 0 type 1 flags 0x0 name bpf_prog_45e2203c2928704d_do_ret_sys_execve 109301967895 0x34830 [0x58]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b3b0 len 0 type 1 flags 0x1 name bpf_prog_bc5697a410556fc2_syscall__execve 109302007356 0x348b0 [0x58]: PERF_RECORD_KSYMBOL addr ffffffffa9b6b3f0 len 0 type 1 flags 0x1 name bpf_prog_45e2203c2928704d_do_ret_sys_execve perf: tools/include/linux/refcount.h:131: refcount_sub_and_test: Assertion `!(new > val)' failed. Here the addresses match the bpf interpreter: # grep -e ffffffffa9b6b530 -e ffffffffa9b6b3b0 -e ffffffffa9b6b3f0 /proc/kallsyms ffffffffa9b6b3b0 t __bpf_prog_run224 ffffffffa9b6b3f0 t __bpf_prog_run192 ffffffffa9b6b530 t __bpf_prog_run32 Fix by not allowing vmlinux_map to be removed by PERF_RECORD_KSYMBOL unregister event. Signed-off-by: Tommi Rantala <[email protected]> --- tools/perf/util/machine.c | 11 ++++++++++- tools/perf/util/symbol.c | 7 +++++++ tools/perf/util/symbol.h | 2 ++ 3 files changed, 19 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 85587de027a5..d93d35463c61 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -786,11 +786,20 @@ static int machine__process_ksymbol_unregister(struct machine *machine, union perf_event *event, struct perf_sample *sample __maybe_unused) { + struct symbol *sym; struct map *map; map = maps__find(&machine->kmaps, event->ksymbol.addr); - if (map) + if (!map) + return 0; + + if (map != machine->vmlinux_map) maps__remove(&machine->kmaps, map); + else { + sym = dso__find_symbol(map->dso, map->map_ip(map, map->start)); + if (sym) + dso__delete_symbol(map->dso, sym); + } return 0; } diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index 5151a8c0b791..6bf8e74ea1d1 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -515,6 +515,13 @@ void dso__insert_symbol(struct dso *dso, struct symbol *sym) } } +void dso__delete_symbol(struct dso *dso, struct symbol *sym) +{ + rb_erase_cached(&sym->rb_node, &dso->symbols); + symbol__delete(sym); + dso__reset_find_symbol_cache(dso); +} + struct symbol *dso__find_symbol(struct dso *dso, u64 addr) { if (dso->last_find_result.addr != addr || dso->last_find_result.symbol == NULL) { diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h index 03e264a27cd3..60345691db09 100644 --- a/tools/perf/util/symbol.h +++ b/tools/perf/util/symbol.h @@ -130,6 +130,8 @@ int dso__load_kallsyms(struct dso *dso, const char *filename, struct map *map); void dso__insert_symbol(struct dso *dso, struct symbol *sym); +void dso__delete_symbol(struct dso *dso, + struct symbol *sym); struct symbol *dso__find_symbol(struct dso *dso, u64 addr); struct symbol *dso__find_symbol_by_name(struct dso *dso, const char *name); -- 2.26.2
