From 537242e606d7980e549444395c4bcedea15da431 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Sun, 29 Mar 2026 11:47:22 +0100
Subject: [PATCH] kernel: handle: add support for allocating a specific handle
 value

---
 include/kernel/handle.h |  1 +
 kernel/handle.c         | 51 ++++++++++++++++++++++++++++++++++++++++-
 sched/task.c            |  7 ++++--
 syscall/task.c          |  6 +++++
 syscall/vm-controller.c |  1 +
 5 files changed, 63 insertions(+), 3 deletions(-)

diff --git a/include/kernel/handle.h b/include/kernel/handle.h
index 98715f4..d23d6eb 100644
--- a/include/kernel/handle.h
+++ b/include/kernel/handle.h
@@ -47,6 +47,7 @@ extern void handle_table_destroy(struct handle_table *tab);
 
 extern kern_status_t handle_table_alloc_handle(
 	struct handle_table *tab,
+	kern_handle_t value,
 	struct handle **out_slot,
 	kern_handle_t *out_handle);
 extern kern_status_t handle_table_free_handle(
diff --git a/kernel/handle.c b/kernel/handle.c
index d1d0df9..8195afd 100644
--- a/kernel/handle.c
+++ b/kernel/handle.c
@@ -109,7 +109,7 @@ static kern_status_t encode_handle_indices(
 	return KERN_OK;
 }
 
-kern_status_t handle_table_alloc_handle(
+static kern_status_t alloc_handle(
 	struct handle_table *tab,
 	struct handle **out_slot,
 	kern_handle_t *out_handle)
@@ -164,6 +164,53 @@ kern_status_t handle_table_alloc_handle(
 	return encode_handle_indices(indices, out_handle);
 }
 
+kern_status_t handle_table_alloc_handle(
+	struct handle_table *tab,
+	kern_handle_t value,
+	struct handle **out_slot,
+	kern_handle_t *out_handle)
+{
+	if (value == KERN_HANDLE_INVALID) {
+		return alloc_handle(tab, out_slot, out_handle);
+	}
+
+	unsigned int indices[MAX_TABLE_DEPTH];
+	if (decode_handle_indices(value, indices) != KERN_OK) {
+		return KERN_HANDLE_INVALID;
+	}
+
+	int i;
+	for (i = 0; i < MAX_TABLE_DEPTH - 1; i++) {
+		struct handle_table *next
+			= tab->t_subtables.t_subtable_list[indices[i]];
+		if (!next) {
+			next = handle_table_create();
+			tab->t_subtables.t_subtable_list[indices[i]] = next;
+		}
+
+		if (!next) {
+			return KERN_NO_MEMORY;
+		}
+
+		tab = next;
+	}
+
+	unsigned int handle_index = indices[i];
+	bitmap_set(tab->t_handles.t_handle_map, handle_index);
+
+	struct handle *out = &tab->t_handles.t_handle_list[handle_index];
+
+	if (out->h_object) {
+		object_unref(out->h_object);
+		out->h_object = NULL;
+		out->h_flags = 0;
+	}
+
+	*out_slot = out;
+	*out_handle = value;
+	return KERN_OK;
+}
+
 kern_status_t handle_table_free_handle(
 	struct handle_table *tab,
 	kern_handle_t handle)
@@ -299,6 +346,7 @@ kern_status_t handle_table_transfer(
 		case KERN_MSG_HANDLE_MOVE:
 			status = handle_table_alloc_handle(
 				dst,
+				KERN_HANDLE_INVALID,
 				&dst_entry,
 				&dst_value);
 			if (status != KERN_OK) {
@@ -318,6 +366,7 @@ kern_status_t handle_table_transfer(
 		case KERN_MSG_HANDLE_COPY:
 			status = handle_table_alloc_handle(
 				dst,
+				KERN_HANDLE_INVALID,
 				&dst_entry,
 				&dst_value);
 			if (status != KERN_OK) {
diff --git a/sched/task.c b/sched/task.c
index 504b204..f5e70c2 100644
--- a/sched/task.c
+++ b/sched/task.c
@@ -352,8 +352,11 @@ kern_status_t task_open_handle(
 	kern_handle_t *out)
 {
 	struct handle *handle_data = NULL;
-	kern_status_t status
-		= handle_table_alloc_handle(task->t_handles, &handle_data, out);
+	kern_status_t status = handle_table_alloc_handle(
+		task->t_handles,
+		KERN_HANDLE_INVALID,
+		&handle_data,
+		out);
 	if (status != KERN_OK) {
 		return status;
 	}
diff --git a/syscall/task.c b/syscall/task.c
index 2b04346..e436d8a 100644
--- a/syscall/task.c
+++ b/syscall/task.c
@@ -30,6 +30,7 @@ kern_status_t sys_task_self(kern_handle_t *out)
 	kern_handle_t handle;
 	kern_status_t status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&handle_slot,
 		&handle);
 	task_unlock_irqrestore(self, flags);
@@ -89,6 +90,7 @@ kern_status_t sys_task_create(
 	kern_handle_t child_handle, space_handle;
 	status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&child_handle_slot,
 		&child_handle);
 	if (status != KERN_OK) {
@@ -99,6 +101,7 @@ kern_status_t sys_task_create(
 
 	status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&space_handle_slot,
 		&space_handle);
 	if (status != KERN_OK) {
@@ -175,6 +178,7 @@ kern_status_t sys_task_create_thread(
 	kern_handle_t out_handle;
 	status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&target_handle,
 		&out_handle);
 	if (status != KERN_OK) {
@@ -236,6 +240,7 @@ kern_status_t sys_task_get_address_space(
 
 	status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&handle_slot,
 		&handle);
 	if (status != KERN_OK) {
@@ -278,6 +283,7 @@ kern_status_t sys_thread_self(kern_handle_t *out)
 	kern_handle_t handle;
 	kern_status_t status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&handle_slot,
 		&handle);
 	task_unlock_irqrestore(self, flags);
diff --git a/syscall/vm-controller.c b/syscall/vm-controller.c
index a1c756e..807891a 100644
--- a/syscall/vm-controller.c
+++ b/syscall/vm-controller.c
@@ -154,6 +154,7 @@ kern_status_t sys_vm_controller_create_object(
 	kern_handle_t out_handle = KERN_HANDLE_INVALID;
 	status = handle_table_alloc_handle(
 		self->t_handles,
+		KERN_HANDLE_INVALID,
 		&out_slot,
 		&out_handle);