Em Mon, Oct 19, 2020 at 10:53:43PM +0200, Jiri Olsa escreveu:
> 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, applied.
- Arnaldo
> 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
> >
>
--
- Arnaldo
