When build_cpu_topo() encounters offline/absent CPUs,
it fails to find any sysfs entries and returns failure.
This leads to build_cpu_topology() and write_cpu_topology()
failing as well.
Because HEADER_CPU_TOPOLOGY has not been written, read leaves
cpu_topology_map NULL and we get NULL ptr deref at:
...
cmd_test
__cmd_test
test_and_print
run_test
test_session_topology
check_cpu_topology
# perf test 36
36: Session topology :
--- start ---
test child forked, pid 14902
templ file: /tmp/perf-test-4CKocW
failed to write feature HEADER_CPU_TOPOLOGY
perf: Segmentation fault
Obtained 9 stack frames.
./perf(sighandler_dump_stack+0x41) [0x5095f1]
/lib64/libc.so.6(+0x35250) [0x7f4b7c3c9250]
./perf(test_session_topology+0x1db) [0x490ceb]
./perf() [0x475b68]
./perf(cmd_test+0x5b9) [0x4763c9]
./perf() [0x4945a3]
./perf(main+0x69f) [0x427e8f]
/lib64/libc.so.6(__libc_start_main+0xf5) [0x7f4b7c3b5b35]
./perf() [0x427fb9]
test child interrupted
---- end ----
Session topology: FAILED!
This patch makes build_cpu_topology() skip offline/absent CPUs,
by checking their presence against cpu_map built from online CPUs.
Signed-off-by: Jan Stancek <jstan...@redhat.com>
---
tools/perf/util/header.c | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index d89c9c7ef4e5..ca0f12fb5fd3 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -503,24 +503,31 @@ static void free_cpu_topo(struct cpu_topo *tp)
static struct cpu_topo *build_cpu_topology(void)
{
- struct cpu_topo *tp;
+ struct cpu_topo *tp = NULL;
void *addr;
u32 nr, i;
size_t sz;
long ncpus;
int ret = -1;
+ struct cpu_map *map;
ncpus = sysconf(_SC_NPROCESSORS_CONF);
if (ncpus < 0)
return NULL;
+ /* build online CPU map */
+ map = cpu_map__new(NULL);
+ if (map == NULL) {
+ pr_debug("failed to get system cpumap\n");
+ return NULL;
+ }
+
nr = (u32)(ncpus & UINT_MAX);
sz = nr * sizeof(char *);
-
addr = calloc(1, sizeof(*tp) + 2 * sz);
if (!addr)
- return NULL;
+ goto out_free;
tp = addr;
tp->cpu_nr = nr;
@@ -530,10 +537,16 @@ static struct cpu_topo *build_cpu_topology(void)
tp->thread_siblings = addr;
for (i = 0; i < nr; i++) {
+ if (!cpu_map__has(map, i))
+ continue;
+
ret = build_cpu_topo(tp, i);
if (ret < 0)
break;
}
+
+out_free:
+ cpu_map__put(map);
if (ret) {
free_cpu_topo(tp);
tp = NULL;
--
1.8.3.1
