fix(bpf): cleanup initialising structs and nested ifs (#1444)

This commit changes all declarae and then initialise code of form below

```
struct foobar x;
x.a = a;
x.b = b;
```

to
```
struct foobar x = { .a = a, .b = b, };
```
The difference in the code produced is as follows

```
;  new_pid_key.pid = cur_pid;                             | pid_time_t new_pid_key = {.pid = cur_pid };
  0: 63 6a fc ff 00 00 00 00	*(u32 *)(r10 - 0x4) = r6  |  0:	79 a1 68 ff 00 00 00 00	r1 = *(u64 *)(r10 - 0x98)
  1: bf a2 00 00 00 00 00 00	r2 = r10                  |  1:	63 1a fc ff 00 00 00 00	*(u32 *)(r10 - 0x4) = r1
  2: 07 02 00 00 fc ff ff ff	r2 += -0x4                |  2:	bf a2 00 00 00 00 00 00	r2 = r10
  3: bf a3 00 00 00 00 00 00	r3 = r10                  |  3:	07 02 00 00 f0 ff ff ff	r2 += -0x10
  4: 07 03 00 00 70 ff ff ff	r3 += -0x90

```

Modifies calc_delta to remove unnecessary pointer deferencing of second
arg - `val`

Signed-off-by: Sunil Thaha <[email protected]>
(cherry picked from commit ac43e26)

bpfassets/libbpf/src/kepler.bpf.c

@@ -96,11 +96,10 @@ int counter_sched_switch = 0;
 static inline u64 get_on_cpu_time(u32 cur_pid, u32 prev_pid, u64 cur_ts)
 {
 	u64 cpu_time = 0;
-	u64 *prev_ts;
-	pid_time_t prev_pid_key, new_pid_key = {};
+	pid_time_t prev_pid_key = { .pid = prev_pid };
+	pid_time_t new_pid_key = { .pid = cur_pid };
 
-	prev_pid_key.pid = prev_pid;
-	prev_ts = bpf_map_lookup_elem(&pid_time, &prev_pid_key);
+	u64 *prev_ts = bpf_map_lookup_elem(&pid_time, &prev_pid_key);
 	if (prev_ts) {
 		// Probably a clock issue where the recorded on-CPU event had a
 		// timestamp later than the recorded off-CPU event, or vice versa.
@@ -109,19 +108,18 @@ static inline u64 get_on_cpu_time(u32 cur_pid, u32 prev_pid, u64 cur_ts)
 			bpf_map_delete_elem(&pid_time, &prev_pid_key);
 		}
 	}
-	new_pid_key.pid = cur_pid;
+
 	bpf_map_update_elem(&pid_time, &new_pid_key, &cur_ts, BPF_NOEXIST);
 	return cpu_time;
 }
 
-static inline u64 calc_delta(u64 *prev_val, u64 *val)
+static inline u64 calc_delta(u64 *prev_val, u64 val)
 {
 	u64 delta = 0;
-
-	if (prev_val) {
-		if (*val > *prev_val)
-			delta = *val - *prev_val;
+	if (prev_val && val > *prev_val) {
+		delta = val - *prev_val;
 	}
+
 	return delta;
 }
 
@@ -138,7 +136,7 @@ static inline u64 get_on_cpu_cycles(u32 *cpu_id)
 
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cpu_cycles, cpu_id);
-	delta = calc_delta(prev_val, &val);
+	delta = calc_delta(prev_val, val);
 	bpf_map_update_elem(&cpu_cycles, cpu_id, &val, BPF_ANY);
 
 	return delta;
@@ -152,12 +150,12 @@ static inline u64 get_on_cpu_instr(u32 *cpu_id)
 
 	error = bpf_perf_event_read_value(
 		&cpu_instructions_event_reader, *cpu_id, &c, sizeof(c));
-	if (error) {
+	if (error)
 		return 0;
-	}
+
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cpu_instructions, cpu_id);
-	delta = calc_delta(prev_val, &val);
+	delta = calc_delta(prev_val, val);
 	bpf_map_update_elem(&cpu_instructions, cpu_id, &val, BPF_ANY);
 
 	return delta;
@@ -176,7 +174,7 @@ static inline u64 get_on_cpu_cache_miss(u32 *cpu_id)
 	}
 	val = c.counter;
 	prev_val = bpf_map_lookup_elem(&cache_miss, cpu_id);
-	delta = calc_delta(prev_val, &val);
+	delta = calc_delta(prev_val, val);
 	bpf_map_update_elem(&cache_miss, cpu_id, &val, BPF_ANY);
 
 	return delta;
@@ -241,10 +239,11 @@ int kepler_sched_switch_trace(struct sched_switch_info *ctx)
 	// create new process metrics
 	cur_pid_metrics = bpf_map_lookup_elem(&processes, &cur_pid);
 	if (!cur_pid_metrics) {
-		process_metrics_t new_process = {};
-		new_process.pid = cur_pid;
-		new_process.tgid = tgid;
-		new_process.cgroup_id = cgroup_id;
+		process_metrics_t new_process = {
+			.pid = cur_pid,
+			.tgid = tgid,
+			.cgroup_id = cgroup_id,
+		};
 		bpf_get_current_comm(&new_process.comm, sizeof(new_process.comm));
 		bpf_map_update_elem(
 			&processes, &cur_pid, &new_process, BPF_NOEXIST);