tetragon: Factor generic_process_filter function

Switch 'enter' check to '!enter' and decrease indent of the
following code, which makes the function more readable and
will ease up following changes.

There's no functional change.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>

bpf/process/generic_calls.h

@@ -570,59 +570,57 @@ FUNC_INLINE int generic_retkprobe(void *ctx, struct bpf_map_def *calls, unsigned
 // msg_generic_hdr structure.
 FUNC_INLINE int generic_process_filter(void)
 {
+	int selectors, pass, curr, zero = 0;
 	struct execve_map_value *enter;
 	struct msg_generic_kprobe *msg;
 	struct msg_execve_key *current;
 	struct msg_selector_data *sel;
-	int curr, zero = 0;
 	bool walker = 0;
-	__u32 ppid;
+	__u32 ppid, *f;
 
 	msg = map_lookup_elem(&process_call_heap, &zero);
 	if (!msg)
 		return 0;
 
 	enter = event_find_curr(&ppid, &walker);
-	if (enter) {
-		int selectors, pass;
-		__u32 *f = map_lookup_elem(&filter_map, &msg->idx);
+	if (!enter)
+		return PFILTER_CURR_NOT_FOUND;
 
-		if (!f)
-			return PFILTER_ERROR;
+	f = map_lookup_elem(&filter_map, &msg->idx);
+	if (!f)
+		return PFILTER_ERROR;
 
-		sel = &msg->sel;
-		current = &msg->current;
+	sel = &msg->sel;
+	current = &msg->current;
 
-		curr = sel->curr;
-		if (curr > MAX_SELECTORS)
-			return process_filter_done(sel, enter, current);
+	curr = sel->curr;
+	if (curr > MAX_SELECTORS)
+		return process_filter_done(sel, enter, current);
 
-		selectors = f[0];
-		/* If no selectors accept process */
-		if (!selectors) {
-			sel->pass = true;
-			return process_filter_done(sel, enter, current);
-		}
+	selectors = f[0];
+	/* If no selectors accept process */
+	if (!selectors) {
+		sel->pass = true;
+		return process_filter_done(sel, enter, current);
+	}
 
-		/* If we get here with reference to uninitialized selector drop */
-		if (selectors <= curr)
-			return process_filter_done(sel, enter, current);
-
-		pass = selector_process_filter(f, curr, enter, msg);
-		if (pass) {
-			/* Verify lost that msg is not null here so recheck */
-			asm volatile("%[curr] &= 0x1f;\n"
-				     : [curr] "+r"(curr));
-			sel->active[curr] = true;
-			sel->active[SELECTORS_ACTIVE] = true;
-			sel->pass |= true;
-		}
-		sel->curr++;
-		if (sel->curr > selectors)
-			return process_filter_done(sel, enter, current);
-		return PFILTER_CONTINUE; /* will iterate to the next selector */
+	/* If we get here with reference to uninitialized selector drop */
+	if (selectors <= curr)
+		return process_filter_done(sel, enter, current);
+
+	pass = selector_process_filter(f, curr, enter, msg);
+	if (pass) {
+		/* Verify lost that msg is not null here so recheck */
+		asm volatile("%[curr] &= 0x1f;\n"
+			     : [curr] "+r"(curr));
+		sel->active[curr] = true;
+		sel->active[SELECTORS_ACTIVE] = true;
+		sel->pass |= true;
 	}
-	return PFILTER_CURR_NOT_FOUND;
+	sel->curr++;
+	if (sel->curr > selectors)
+		return process_filter_done(sel, enter, current);
+	return PFILTER_CONTINUE; /* will iterate to the next selector */
 }
 
 FUNC_INLINE int filter_args(struct msg_generic_kprobe *e, int selidx, bool is_entry)