kernel/proc: implement `process_next` for simple process iteration

2 files changed, 28 insertions, 15 deletions

diff --git a/src/kernel/proc.c b/src/kernel/proc.c
index 944f5b9..ca1b2ec 100644
--- a/src/kernel/proc.c
+++ b/src/kernel/proc.c
@@ -95,21 +95,24 @@ _Noreturn void process_idle(void) {
 	}
 }
 
-// TODO there's no check for going past the stack - VULN
-static size_t _process_find_recursive(
-		enum process_state target, struct process *iter,
-		struct process **buf, size_t pos, size_t max)
-{
-	while (pos < max && iter) {
-		if (iter->state == target)
-			buf[pos++] = iter;
-
-		// DFS
-		pos = _process_find_recursive(target, iter->child, buf, pos, max);
-
-		iter = iter->sibling;
+struct process *process_next(struct process *p) {
+	/* is a weird depth-first search, the search order is:
+	 *         1
+	 *        / \
+	 *       2   5
+	 *      /|   |\
+	 *     3 4   6 7
+	 */
+	if (!p)	return NULL;
+	if (p->child)	return p->child;
+	if (p->sibling)	return p->sibling;
+
+	/* looking at the diagram above - we're at 4, want to find 5 */
+	while (!p->sibling) {
+		p = p->parent;
+		if (!p) return NULL;
 	}
-	return pos;
+	return p->sibling;
 }
 
 struct process *process_find(enum process_state target) {
@@ -119,7 +122,14 @@ struct process *process_find(enum process_state target) {
 }
 
 size_t process_find_multiple(enum process_state target, struct process **buf, size_t max) {
-	return _process_find_recursive(target, process_first, buf, 0, max);
+	size_t i = 0;
+	for (struct process *p = process_first;
+		i < max && p;
+		p = process_next(p))
+	{
+		if (p->state == target) buf[i++] = p;
+	}
+	return i;
 }
 
 handle_t process_find_handle(struct process *proc) {
diff --git a/src/kernel/proc.h b/src/kernel/proc.h
index d754522..1d84b7f 100644
--- a/src/kernel/proc.h
+++ b/src/kernel/proc.h
@@ -64,6 +64,9 @@ _Noreturn void process_switch_any(void); // switches to any running process
 /** If there are any processes waiting for IRQs, wait with them. Otherwise, shut down */
 _Noreturn void process_idle(void);
 
+/** Used for iterating over all processes */
+struct process *process_next(struct process *);
+
 struct process *process_find(enum process_state);
 size_t process_find_multiple(enum process_state, struct process **buf, size_t max);