fix(bpf): Fix issue introduced with bpf refactor

This fixes a few issues identified with the bpf code
format and refactor.

1. Zero initialize all variables
2. Use the bpf_perf_event_read_value helper exlusively

In addition, add some logging around eBPF array resizing.

Fixes: #1402 #1411

Signed-off-by: Dave Tucker <[email protected]>

bpfassets/libbpf/src/kepler.bpf.c

@@ -95,8 +95,9 @@ int counter_sched_switch = 0;
 
 static inline u64 get_on_cpu_time(u32 cur_pid, u32 prev_pid, u64 cur_ts)
 {
-	u64 cpu_time, *prev_ts;
-	pid_time_t prev_pid_key, new_pid_key;
+	u64 cpu_time = 0;
+	u64 *prev_ts;
+	pid_time_t prev_pid_key, new_pid_key = {};
 
 	prev_pid_key.pid = prev_pid;
 	prev_ts = bpf_map_lookup_elem(&pid_time, &prev_pid_key);
@@ -115,7 +116,7 @@ static inline u64 get_on_cpu_time(u32 cur_pid, u32 prev_pid, u64 cur_ts)
 
 static inline u64 calc_delta(u64 *prev_val, u64 *val)
 {
-	u64 delta;
+	u64 delta = 0;
 
 	if (prev_val) {
 		if (*val > *prev_val)
@@ -127,14 +128,14 @@ static inline u64 calc_delta(u64 *prev_val, u64 *val)
 static inline u64 get_on_cpu_cycles(u32 *cpu_id)
 {
 	u64 delta, val, *prev_val;
-	struct bpf_perf_event_value c;
 	int error;
+	struct bpf_perf_event_value c = {};
+
+	error = bpf_perf_event_read_value(
+		&cpu_cycles_event_reader, *cpu_id, &c, sizeof(c));
+	if (error)
+		return 0;
 
-	// TODO: Fix Verifier errors upon changing this to bpf_perf_event_read_value
-	error = bpf_perf_event_read(&cpu_cycles_event_reader, *cpu_id);
-	if (error < 0) {
-		return delta;
-	}
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cpu_cycles, cpu_id);
 	delta = calc_delta(prev_val, &val);
@@ -147,12 +148,12 @@ static inline u64 get_on_cpu_instr(u32 *cpu_id)
 {
 	u64 delta, val, *prev_val;
 	int error;
-	struct bpf_perf_event_value c;
+	struct bpf_perf_event_value c = {};
 
 	error = bpf_perf_event_read_value(
 		&cpu_instructions_event_reader, *cpu_id, &c, sizeof(c));
 	if (error) {
-		return delta;
+		return 0;
 	}
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cpu_instructions, cpu_id);
@@ -166,12 +167,12 @@ static inline u64 get_on_cpu_cache_miss(u32 *cpu_id)
 {
 	u64 delta, val, *prev_val;
 	int error;
-	struct bpf_perf_event_value c;
+	struct bpf_perf_event_value c = {};
 
 	error = bpf_perf_event_read_value(
 		&cache_miss_event_reader, *cpu_id, &c, sizeof(c));
 	if (error) {
-		return delta;
+		return 0;
 	}
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cache_miss, cpu_id);
@@ -203,7 +204,8 @@ int kepler_sched_switch_trace(struct sched_switch_info *ctx)
 	u64 pid_tgid, cgroup_id, cur_ts;
 	pid_t cur_pid;
 
-	struct process_metrics_t *cur_pid_metrics, *prev_pid_metrics, buf;
+	struct process_metrics_t *cur_pid_metrics, *prev_pid_metrics;
+	struct process_metrics_t buf;
 
 	if (SAMPLE_RATE > 0) {
 		if (counter_sched_switch > 0) {
@@ -236,7 +238,7 @@ int kepler_sched_switch_trace(struct sched_switch_info *ctx)
 		prev_pid_metrics->cache_miss += buf.cache_miss;
 	}
 
-	// creat new process metrics
+	// create new process metrics
 	cur_pid_metrics = bpf_map_lookup_elem(&processes, &cur_pid);
 	if (!cur_pid_metrics) {
 		process_metrics_t new_process = {};

pkg/bpfassets/attacher/libbpf_attacher.go

@@ -110,6 +110,7 @@ func attachLibbpfModule() (*bpf.Module, error) {
 		return nil, fmt.Errorf("failed to load module: %v", err)
 	}
 	// resize array entries
+	klog.Infof("%d CPU cores detected. Resizing eBPF Perf Event Arrays", cpuCores)
 	for _, arrayName := range bpfArrays {
 		err = resizeArrayEntries(arrayName, cpuCores)
 		if err != nil {