Commit-ID: 721f0dfc3ce821c6a32820ab63edfb48ed4af075
Gitweb: https://git.kernel.org/tip/721f0dfc3ce821c6a32820ab63edfb48ed4af075
Author: Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Fri, 17 Aug 2018 13:45:56 +0200
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Mon, 20 Aug 2018 08:54:59 -0300
perf python: Fix pyrf_evlist__read_on_cpu() interface
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@xxxxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Joe Mario <jmario@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20180817114556.28000-3-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
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 f74fbb652a4f..ce501ba14b08 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;
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