From: Jiri Olsa jolsa@kernel.org
[ Upstream commit 721f0dfc3ce821c6a32820ab63edfb48ed4af075 ]
Jaroslav reported errors from valgrind over perf python script:
# echo 0 > /sys/devices/system/cpu/cpu4/online # valgrind ./test.py ==7524== Memcheck, a memory error detector ... ==7524== Command: ./test.py ==7524== pid 7526 exited ==7524== Invalid read of size 8 ==7524== at 0xCC2C2B3: perf_mmap__read_forward (evlist.c:780) ==7524== by 0xCC2A681: pyrf_evlist__read_on_cpu (python.c:959) ... ==7524== Address 0x65c4868 is 16 bytes after a block of size 459,36.. ==7524== at 0x4C2B955: calloc (vg_replace_malloc.c:711) ==7524== by 0xCC2F484: zalloc (util.h:35) ==7524== by 0xCC2F484: perf_evlist__alloc_mmap (evlist.c:978) ...
The reason for this is in the python interface, that allows a script to pass arbitrary cpu number, which is then used to access struct perf_evlist::mmap array. That's obviously wrong and works only when if all cpus are available and fails if some cpu is missing, like in the example above.
This patch makes pyrf_evlist__read_on_cpu() search the evlist's maps array for the proper map to access.
It's linear search at the moment. Based on the way how is the read_on_cpu used, I don't think we need to be fast in here. But we could add some hash in the middle to make it fast/er.
We don't allow python interface to set write_backward event attribute, so it's safe to check only evlist's mmaps.
Reported-by: Jaroslav Škarvada jskarvad@redhat.com Signed-off-by: Jiri Olsa jolsa@kernel.org Cc: Alexander Shishkin alexander.shishkin@linux.intel.com Cc: David Ahern dsahern@gmail.com Cc: Joe Mario jmario@redhat.com Cc: Namhyung Kim namhyung@kernel.org Cc: Peter Zijlstra peterz@infradead.org Link: http://lkml.kernel.org/r/20180817114556.28000-3-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- tools/perf/util/python.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c index 863b61478edd..eefc56b4b0df 100644 --- a/tools/perf/util/python.c +++ b/tools/perf/util/python.c @@ -11,6 +11,7 @@ #include "cpumap.h" #include "print_binary.h" #include "thread_map.h" +#include "mmap.h"
#if PY_MAJOR_VERSION < 3 #define _PyUnicode_FromString(arg) \ @@ -976,6 +977,20 @@ static PyObject *pyrf_evlist__add(struct pyrf_evlist *pevlist, return Py_BuildValue("i", evlist->nr_entries); }
+static struct perf_mmap *get_md(struct perf_evlist *evlist, int cpu) +{ + int i; + + for (i = 0; i < evlist->nr_mmaps; i++) { + struct perf_mmap *md = &evlist->mmap[i]; + + if (md->cpu == cpu) + return md; + } + + return NULL; +} + static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist, PyObject *args, PyObject *kwargs) { @@ -990,7 +1005,10 @@ static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist, &cpu, &sample_id_all)) return NULL;
- md = &evlist->mmap[cpu]; + md = get_md(evlist, cpu); + if (!md) + return NULL; + if (perf_mmap__read_init(md) < 0) goto end;