lkml.org 
[lkml]   [2018]   [Mar]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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

\
 
 \ /
  Last update: 2018-03-09 16:18    [W:0.048 / U:0.924 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site