kernel: add a syscall to query generic information about an object

include/kernel/syscall.h

@@ -195,6 +195,9 @@ extern kern_status_t sys_msg_write(
 extern kern_status_t sys_kern_object_wait(
 	kern_wait_item_t *items,
 	size_t nr_items);
+extern kern_status_t sys_kern_object_query(
+	kern_handle_t object,
+	kern_object_info_t *out);
 
 extern kern_status_t sys_vm_controller_create(kern_handle_t *out);
 extern kern_status_t sys_vm_controller_recv(

libmango/arch/x86_64/syscall.S

@@ -105,6 +105,7 @@ SYSCALL_GATE vm_controller_detach_object SYS_VM_CONTROLLER_DETACH_OBJECT 2
 SYSCALL_GATE vm_controller_supply_pages SYS_VM_CONTROLLER_SUPPLY_PAGES 6
 
 SYSCALL_GATE kern_object_wait SYS_KERN_OBJECT_WAIT 2
+SYSCALL_GATE kern_object_query SYS_KERN_OBJECT_QUERY 2
 
 SYSCALL_GATE futex_wait SYS_FUTEX_WAIT 3
 SYSCALL_GATE futex_wake SYS_FUTEX_WAKE 3

libmango/include-user/mango/object.h

@@ -4,5 +4,8 @@
 #include <mango/types.h>
 
 extern kern_status_t kern_object_wait(kern_wait_item_t *items, size_t nr_items);
+extern kern_status_t kern_object_query(
+	kern_handle_t handle,
+	kern_object_info_t *out);
 
 #endif

libmango/include/mango/syscall.h

@@ -49,5 +49,6 @@
 #define SYS_VM_CONTROLLER_SUPPLY_PAGES  46
 #define SYS_FUTEX_WAIT                  47
 #define SYS_FUTEX_WAKE                  48
+#define SYS_KERN_OBJECT_QUERY           49
 
 #endif

libmango/include/mango/types.h

@@ -109,6 +109,10 @@ typedef unsigned short equeue_packet_type_t;
 
 typedef unsigned int umode_t;
 
+typedef struct {
+	koid_t obj_id;
+} kern_object_info_t;
+
 typedef struct {
 	virt_addr_t io_base;
 	size_t io_len;

syscall/dispatch.c

@@ -52,6 +52,7 @@ static const virt_addr_t syscall_table[] = {
 		VM_CONTROLLER_SUPPLY_PAGES,
 		vm_controller_supply_pages),
 	SYSCALL_TABLE_ENTRY(KERN_OBJECT_WAIT, kern_object_wait),
+	SYSCALL_TABLE_ENTRY(KERN_OBJECT_QUERY, kern_object_query),
 	SYSCALL_TABLE_ENTRY(FUTEX_WAIT, futex_wait),
 	SYSCALL_TABLE_ENTRY(FUTEX_WAKE, futex_wake),
 };

syscall/object.c

@@ -80,3 +80,32 @@ cleanup:
 	self_thread->tr_state = THREAD_READY;
 	return status;
 }
+
+kern_status_t sys_kern_object_query(
+	kern_handle_t object_handle,
+	kern_object_info_t *out)
+{
+	struct task *self = current_task();
+
+	if (!out) {
+		return KERN_INVALID_ARGUMENT;
+	}
+
+	if (!validate_access_w(self, out, sizeof *out)) {
+		return KERN_MEMORY_FAULT;
+	}
+
+	struct object *obj = NULL;
+	handle_flags_t flags = 0;
+	kern_status_t status
+		= task_resolve_handle(self, object_handle, &obj, &flags);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	out->obj_id = obj->ob_id;
+
+	object_unref(obj);
+
+	return KERN_OK;
+}