perf tools: Replace _SC_NPROCESSORS_CONF with max_present_cpu in cpu_topology_map

There are 2 problems wrt. cpu_topology_map on systems with sparse CPUs:

1. offline/absent CPUs will have their socket_id and core_id set to -1
which triggers:
"socket_id number is too big.You may need to upgrade the perf tool."

2. size of cpu_topology_map (perf_env.cpu[]) is allocated based on
_SC_NPROCESSORS_CONF, but can be indexed with CPU ids going above.
Users of perf_env.cpu[] are using CPU id as index. This can lead
to read beyond what was allocated:
==19991== Invalid read of size 4
==19991== at 0x490CEB: check_cpu_topology (topology.c:69)
==19991== by 0x490CEB: test_session_topology (topology.c:106)
...

For example:
_SC_NPROCESSORS_CONF == 16
available: 2 nodes (0-1)
node 0 cpus: 0 6 8 10 16 22 24 26
node 0 size: 12004 MB
node 0 free: 9470 MB
node 1 cpus: 1 7 9 11 23 25 27
node 1 size: 12093 MB
node 1 free: 9406 MB
node distances:
node 0 1
0: 10 20
1: 20 10

This patch changes HEADER_NRCPUS.nr_cpus_available from _SC_NPROCESSORS_CONF
to max_present_cpu and updates any user of cpu_topology_map to iterate
with nr_cpus_avail.

As a consequence HEADER_CPU_TOPOLOGY core_id and socket_id lists get longer,
but maintain compatibility with pre-patch state - index to cpu_topology_map is
CPU id.

perf test 36 -v
36: Session topology :
--- start ---
test child forked, pid 22211
templ file: /tmp/perf-test-gmdX5i
CPU 0, core 0, socket 0
CPU 1, core 0, socket 1
CPU 6, core 10, socket 0
CPU 7, core 10, socket 1
CPU 8, core 1, socket 0
CPU 9, core 1, socket 1
CPU 10, core 9, socket 0
CPU 11, core 9, socket 1
CPU 16, core 0, socket 0
CPU 22, core 10, socket 0
CPU 23, core 10, socket 1
CPU 24, core 1, socket 0
CPU 25, core 1, socket 1
CPU 26, core 9, socket 0
CPU 27, core 9, socket 1
test child finished with 0
---- end ----
Session topology: Ok

Signed-off-by: Jan Stancek <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-stat.c

···
 
 	cpu = map->map[idx];
 
-	if (cpu >= env->nr_cpus_online)
+	if (cpu >= env->nr_cpus_avail)
 		return -1;
 
 	return cpu;

tools/perf/tests/topology.c

···
 	session = perf_session__new(&file, false, NULL);
 	TEST_ASSERT_VAL("can't get session", session);
 
-	for (i = 0; i < session->header.env.nr_cpus_online; i++) {
+	for (i = 0; i < session->header.env.nr_cpus_avail; i++) {
+		if (!cpu_map__has(map, i))
+			continue;
 		pr_debug("CPU %d, core %d, socket %d\n", i,
 			 session->header.env.cpu[i].core_id,
 			 session->header.env.cpu[i].socket_id);

tools/perf/util/env.c

···
 		return 0;
 
 	if (env->nr_cpus_avail == 0)
-		env->nr_cpus_avail = sysconf(_SC_NPROCESSORS_CONF);
+		env->nr_cpus_avail = cpu__max_present_cpu();
 
 	nr_cpus = env->nr_cpus_avail;
 	if (nr_cpus == -1)

tools/perf/util/header.c

···
 	u32 nrc, nra;
 	int ret;
 
-	nr = sysconf(_SC_NPROCESSORS_CONF);
-	if (nr < 0)
-		return -1;
-
-	nrc = (u32)(nr & UINT_MAX);
+	nrc = cpu__max_present_cpu();
 
 	nr = sysconf(_SC_NPROCESSORS_ONLN);
 	if (nr < 0)
···
 	int ret = -1;
 	struct cpu_map *map;
 
-	ncpus = sysconf(_SC_NPROCESSORS_CONF);
-	if (ncpus < 0)
-		return NULL;
+	ncpus = cpu__max_present_cpu();
 
 	/* build online CPU map */
 	map = cpu_map__new(NULL);
···
 {
 	int nr, i;
 	char *str;
-	int cpu_nr = ph->env.nr_cpus_online;
+	int cpu_nr = ph->env.nr_cpus_avail;
 
 	nr = ph->env.nr_sibling_cores;
 	str = ph->env.sibling_cores;
···
 	u32 nr, i;
 	char *str;
 	struct strbuf sb;
-	int cpu_nr = ph->env.nr_cpus_online;
+	int cpu_nr = ph->env.nr_cpus_avail;
 	u64 size = 0;
 
 	ph->env.cpu = calloc(cpu_nr, sizeof(*ph->env.cpu));
···
 		if (ph->needs_swap)
 			nr = bswap_32(nr);
 
-		if (nr > (u32)cpu_nr) {
+		if (nr != (u32)-1 && nr > (u32)cpu_nr) {
 			pr_debug("socket_id number is too big."
 				 "You may need to upgrade the perf tool.\n");
 			goto free_cpu;