Messages in this thread | | | Date | Fri, 9 Mar 2018 12:17:34 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH] perf stat: Fix core dump when flag T is used |
| |
Em Thu, Mar 08, 2018 at 03:57:35PM +0100, Thomas Richter escreveu: > Executing command 'perf stat -T -- ls' dumps core on x86 and s390. > Here is the call back chain (done on x86): > # gdb ./perf > .... > (gdb) r stat -T -- ls > ... > Program received signal SIGSEGV, Segmentation fault. > 0x00007ffff56d1963 in vasprintf () from /lib64/libc.so.6 > (gdb) where > #0 0x00007ffff56d1963 in vasprintf () from /lib64/libc.so.6 > #1 0x00007ffff56ae484 in asprintf () from /lib64/libc.so.6 > #2 0x00000000004f1982 in __parse_events_add_pmu (parse_state=0x7fffffffd580, > list=0xbfb970, name=0xbf3ef0 "cpu", > head_config=0xbfb930, auto_merge_stats=false) at util/parse-events.c:1233 > #3 0x00000000004f1c8e in parse_events_add_pmu (parse_state=0x7fffffffd580, > list=0xbfb970, name=0xbf3ef0 "cpu", > head_config=0xbfb930) at util/parse-events.c:1288 > #4 0x0000000000537ce3 in parse_events_parse (_parse_state=0x7fffffffd580, > scanner=0xbf4210) at util/parse-events.y:234 > #5 0x00000000004f2c7a in parse_events__scanner (str=0x6b66c0 > "task-clock,{instructions,cycles,cpu/cycles-t/,cpu/tx-start/}", > parse_state=0x7fffffffd580, start_token=258) at util/parse-events.c:1673 > #6 0x00000000004f2e23 in parse_events (evlist=0xbe9990, str=0x6b66c0 > "task-clock,{instructions,cycles,cpu/cycles-t/,cpu/tx-start/}", err=0x0) > at util/parse-events.c:1713 > #7 0x000000000044e137 in add_default_attributes () at builtin-stat.c:2281 > #8 0x000000000044f7b5 in cmd_stat (argc=1, argv=0x7fffffffe3b0) at > builtin-stat.c:2828 > #9 0x00000000004c8b0f in run_builtin (p=0xab01a0 <commands+288>, argc=4, > argv=0x7fffffffe3b0) at perf.c:297 > #10 0x00000000004c8d7c in handle_internal_command (argc=4, > argv=0x7fffffffe3b0) at perf.c:349 > #11 0x00000000004c8ece in run_argv (argcp=0x7fffffffe20c, > argv=0x7fffffffe200) at perf.c:393 > #12 0x00000000004c929c in main (argc=4, argv=0x7fffffffe3b0) at perf.c:537 > (gdb) > > It turns out that a NULL pointer is referenced. Here are the > function calls: > > ... > cmd_stat() > +---> add_default_attributes() > +---> parse_events(evsel_list, transaction_attrs, NULL); > 3rd parameter set to NULL > > Function parse_events(xx, xx, struct parse_events_error *err) dives > into a bison generated scanner and creates > parser state information for it first: > > struct parse_events_state parse_state = { > .list = LIST_HEAD_INIT(parse_state.list), > .idx = evlist->nr_entries, > .error = err, <--- NULL POINTER !!! > .evlist = evlist, > }; > > Now various functions inside the bison scanner are called to end up > in __parse_events_add_pmu(struct parse_events_state *parse_state, ..) > with first parameter being a pointer to above structure definition. > > Now the PMU event name is not found (because being executed in a VM) > and this function tries to create an error message with > asprintf(&parse_state->error.str, ....) > which references a NULL pointer and dumps core. > > Fix this by providing a pointer to the necessary error information > instead of NULL. Technically only the else part is needed to avoid > the core dump, just lets be save... > > Signed-off-by: Thomas Richter <tmricht@linux.vnet.ibm.com> > --- > tools/perf/builtin-stat.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index 98bf9d32f222..86c8c8a9229c 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -2274,11 +2274,16 @@ static int add_default_attributes(void) > return 0; > > if (transaction_run) { > + struct parse_events_error errinfo; > + > if (pmu_have_event("cpu", "cycles-ct") && > pmu_have_event("cpu", "el-start")) > - err = parse_events(evsel_list, transaction_attrs, NULL); > + err = parse_events(evsel_list, transaction_attrs, > + &errinfo); > else > - err = parse_events(evsel_list, transaction_limited_attrs, NULL); > + err = parse_events(evsel_list, > + transaction_limited_attrs, > + &errinfo); > if (err) { > fprintf(stderr, "Cannot set up transaction events\n"); > return -1;
Ok, I'm applying this, but then I think some other patch, on top of this, is in demand to actually use that errinfo filled struct to tell something more descriptive to the user in that fprintf() call?
- Arnaldo
| |