Messages in this thread | | | Subject | Re: perf segmentation fault from NULL dereference | From | John Garry <> | Date | Tue, 2 Oct 2018 11:41:36 +0100 |
| |
>> I am suspicious that this is a real issue, as this patch has been in >> mainline for some time... >> >> This simple change fixes the issue me: >> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c >> index 91e6d9c..f4fd826 100644 >> --- a/tools/perf/util/header.c >> +++ b/tools/perf/util/header.c >> @@ -3576,7 +3576,7 @@ int perf_event__process_feature(struct perf_tool >> *tool, >> int max, err; >> u16 type; >> >> - if (!evsel->own_cpus) >> + if (!evsel->own_cpus || !(evsel->attr.read_format & PERF_FORMAT_ID)) // >> roundabout check for !evsel->id >> return 0; >> >> ev = cpu_map_data__alloc(evsel->own_cpus, &size, &type, &max); >> >> It turns out that evsel->id is NULL on a call to >> perf_event__process_feature(), which upsets this code: >> >> ev->header.type = PERF_RECORD_EVENT_UPDATE; >> ev->header.size = (u16)size; >> ev->type = PERF_EVENT_UPDATE__CPUS; >> ev->id = evsel->id[0]; >> >> Please me let me know if a valid issue so we can get a fix in. > > yea, I can see how we can get here with event having > its own CPUs, and we allocate the id array later at > the time we map the event > > I wonder instead of skipping on this feature, we should > allocate the id array, like below > > I did not test that.. need to find the server having event > with its own cpus.. also need to make sure evsel->cpus is > the way to go in here >
Thanks for the fix, but I got this: root@localhost:~# ./perf_debug_ record -e armv8_pmuv3_0/br_mis_pred/ sleep 1 Couldn't synthesize evsel cpus. root@localhost:~#
> thanks, > jirka > > > --- > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c > index 1ec1d9bc2d63..fb2a0dab3978 100644 > --- a/tools/perf/util/header.c > +++ b/tools/perf/util/header.c > @@ -29,6 +29,7 @@ > #include "symbol.h" > #include "debug.h" > #include "cpumap.h" > +#include "thread_map.h" > #include "pmu.h" > #include "vdso.h" > #include "strbuf.h" > @@ -3579,6 +3580,11 @@ perf_event__synthesize_event_update_cpus(struct perf_tool *tool, > if (!evsel->own_cpus) > return 0; > > + if (!evsel->id ||
for my test, evsel->id is NULL
> + perf_evsel__alloc_id(evsel, cpu_map__nr(evsel->cpus), > + thread_map__nr(evsel->threads)))
and then this function is not called as we return immediately. So did you really want this:
if (!evsel->id && perf_evsel__alloc_id(...)) return -ENOMEM;
This looks to work:
root@localhost:~# ./perf_debug_ record -e armv8_pmuv3_0/br_mis_pred/ sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (7 samples) ] root@localhost:~# ./perf_debug_ report # To display the perf.data header info, please use --header/--header-only option # # # Total Lost Samples: 0 # # Samples: 7 of event 'armv8_pmuv3_0/br_mis_pred/' # Event count (approx.): 8260 # # Overhead Command Shared Object Symbol # ........ ....... ................. ...................... # 78.28% sleep libc-2.23.so [.] 0x00000000000faef0 20.53% sleep [kernel.kallsyms] [k] vmacache_find 1.09% sleep [kernel.kallsyms] [k] find_vma 0.10% perf_de [kernel.kallsyms] [k] perf_event_exec
# # (Cannot load tips.txt file, please install perf!) # root@localhost:~#
> + return -ENOMEM; > + > ev = cpu_map_data__alloc(evsel->own_cpus, &size, &type, &max); > if (!ev) > return -ENOMEM; > > . >
Thanks, John
| |