[kernel] Make capabilities/handles global

Instead of handles / capabilities having numeric ids that are only valid
for the owning process, they are now global in a system capabilities
table. This will allow for specifying capabilities in IPC that doesn't
need to be kernel-controlled.

Processes will still need to be granted access to given capabilities,
but that can become a simpler system call than the current method of
sending them through mailbox messages (and worse, having to translate
every one into a new capability like was the case before). In order to
track which handles a process has access to, a new node_set based on
node_map allows for an efficient storage and lookup of handles.

src/kernel/syscalls/helpers.h

@@ -4,6 +4,7 @@
 
 #include <j6/types.h>
 
+#include "capabilities.h"
 #include "objects/kobject.h"
 #include "objects/process.h"
 
@@ -12,41 +13,43 @@ namespace syscalls {
 template <typename T, typename... Args>
 T * construct_handle(j6_handle_t *id, Args... args)
 {
-    obj::process &p = obj::process::current();
     T *o = new T {args...};
-    *id = p.add_handle(o, T::creation_caps);
+    *id = g_cap_table.create(o, T::creation_caps);
+
+    obj::process &p = obj::process::current();
+    p.add_handle(*id);
+
     return o;
 }
 
 template <typename T>
-obj::handle * get_handle(j6_handle_t id)
+j6_status_t get_handle(j6_handle_t id, j6_cap_t caps, T *&object)
 {
+    capability *capdata = g_cap_table.find(id);
+    if (!capdata || capdata->type != T::type)
+        return j6_err_invalid_arg;
+
     obj::process &p = obj::process::current();
-    obj::handle *h = p.lookup_handle(id);
-    if (!h || h->type() != T::type)
-        return nullptr;
-    return h;
+    if (!p.has_handle(id) || (capdata->caps & caps) != caps)
+        return j6_err_denied;
+
+    object = static_cast<T*>(capdata->object);
+    return j6_status_ok;
 }
 
 template <>
-inline obj::handle * get_handle<obj::kobject>(j6_handle_t id)
+inline j6_status_t get_handle<obj::kobject>(j6_handle_t id, j6_cap_t caps, obj::kobject *&object)
 {
+    capability *capdata = g_cap_table.find(id);
+    if (!capdata)
+        return j6_err_invalid_arg;
+
     obj::process &p = obj::process::current();
-    return p.lookup_handle(id);
+    if (!p.has_handle(id) || (capdata->caps & caps) != caps)
+        return j6_err_denied;
+
+    object = capdata->object;
+    return j6_status_ok;
 }
 
-template <typename T>
-T * remove_handle(j6_handle_t id)
-{
-    obj::handle *h = get_handle<T>(id);
-    T *o = nullptr;
-
-    if (h) {
-        o = h->object;
-        obj::process &p = obj::process::current();
-        p.remove_handle(id);
-    }
-    return o;
-}
-
-}
+} // namespace syscalls