bpftool: profile online CPUs instead of possible

The number of online cpu may be not equal to possible cpu.
"bpftool prog profile" can not create pmu event on possible
but on online cpu.

$ dmidecode -s system-product-name
PowerEdge R620
$ cat /sys/devices/system/cpu/possible
0-47
$ cat /sys/devices/system/cpu/online
0-31

Disable cpu dynamically:
$ echo 0 > /sys/devices/system/cpu/cpuX/online

If one cpu is offline, perf_event_open will return ENODEV.
To fix this issue:
* check value returned and skip offline cpu.
* close pmu_fd immediately on error path, avoid fd leaking.

Fixes: 47c09d6a9f67 ("bpftool: Introduce "prog profile" command")
Signed-off-by: Tonghao Zhang <[email protected]>
Cc: Quentin Monnet <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: Song Liu <[email protected]>
Cc: Yonghong Song <[email protected]>
Cc: John Fastabend <[email protected]>
Cc: KP Singh <[email protected]>
Cc: Stanislav Fomichev <[email protected]>
Cc: Hao Luo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Acked-by: John Fastabend <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>

1 files changed, 30 insertions, 8 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index cfc9fdc1e863..e87738dbffc1 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -2233,10 +2233,38 @@ static void profile_close_perf_events(struct profiler_bpf *obj)
 	profile_perf_event_cnt = 0;
 }
 
+static int profile_open_perf_event(int mid, int cpu, int map_fd)
+{
+	int pmu_fd;
+
+	pmu_fd = syscall(__NR_perf_event_open, &metrics[mid].attr,
+			 -1 /*pid*/, cpu, -1 /*group_fd*/, 0);
+	if (pmu_fd < 0) {
+		if (errno == ENODEV) {
+			p_info("cpu %d may be offline, skip %s profiling.",
+				cpu, metrics[mid].name);
+			profile_perf_event_cnt++;
+			return 0;
+		}
+		return -1;
+	}
+
+	if (bpf_map_update_elem(map_fd,
+				&profile_perf_event_cnt,
+				&pmu_fd, BPF_ANY) ||
+	    ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0)) {
+		close(pmu_fd);
+		return -1;
+	}
+
+	profile_perf_events[profile_perf_event_cnt++] = pmu_fd;
+	return 0;
+}
+
 static int profile_open_perf_events(struct profiler_bpf *obj)
 {
 	unsigned int cpu, m;
-	int map_fd, pmu_fd;
+	int map_fd;
 
 	profile_perf_events = calloc(
 		sizeof(int), obj->rodata->num_cpu * obj->rodata->num_metric);
@@ -2255,17 +2283,11 @@ static int profile_open_perf_events(struct profiler_bpf *obj)
 		if (!metrics[m].selected)
 			continue;
 		for (cpu = 0; cpu < obj->rodata->num_cpu; cpu++) {
-			pmu_fd = syscall(__NR_perf_event_open, &metrics[m].attr,
-					 -1/*pid*/, cpu, -1/*group_fd*/, 0);
-			if (pmu_fd < 0 ||
-			    bpf_map_update_elem(map_fd, &profile_perf_event_cnt,
-						&pmu_fd, BPF_ANY) ||
-			    ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0)) {
+			if (profile_open_perf_event(m, cpu, map_fd)) {
 				p_err("failed to create event %s on cpu %d",
 				      metrics[m].name, cpu);
 				return -1;
 			}
-			profile_perf_events[profile_perf_event_cnt++] = pmu_fd;
 		}
 	}
 	return 0;