On Fri, Oct 16, 2020 at 02:47:18PM +0300, Tommi Rantala wrote: > 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]>
nice, I almost forgot about non jit mode by now ;-) Acked/Tested-by: Jiri Olsa <[email protected]> thanks, jirka > --- > 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 >
