[kernel] Add capabilities to handles

This change finally adds capabilities to handles. Included changes:

- j6_handle_t is now again 64 bits, with the highest 8 bits being a type
  code, and the next highest 24 bits being the capability mask, so that
  programs can check type/caps without calling the kernel.
- The definitions grammar now includes a `capabilities [ ]` section on
  objects, to list what capabilities are relevant.
- j6/caps.h is auto-generated from object capability lists
- init_libj6 again sets __handle_self and __handle_sys, this is a bit
  of a hack.
- A new syscall, j6_handle_list, will return the list of existing
  handles owned by the calling process.
- syscall_verify.cpp.cog now actually checks that the needed
  capabilities exist on handles before allowing the call.

src/kernel/objects/process.h

@@ -2,6 +2,7 @@
 /// \file process.h
 /// Definition of process kobject types
 
+#include <j6/caps.h>
 #include <util/map.h>
 #include <util/vector.h>
 
@@ -17,10 +18,10 @@ class process :
 {
 public:
     /// Capabilities on a newly constructed process handle
-    constexpr static j6_cap_t creation_caps = 0;
+    constexpr static j6_cap_t creation_caps = j6_cap_process_all;
 
     /// Capabilities on a process to itself
-    constexpr static j6_cap_t self_caps = 0;
+    constexpr static j6_cap_t self_caps = j6_cap_process_all;
 
     /// Top of memory area where thread stacks are allocated
     constexpr static uintptr_t stacks_top = 0x0000800000000000;
@@ -74,13 +75,19 @@ public:
     /// \returns     Pointer to the handle struct, or null if not found
     handle * lookup_handle(j6_handle_t handle);
 
+    /// Get the list of handle ids this process owns
+    /// \arg handles  Pointer to an array of handles to copy into
+    /// \arg len      Size of the array
+    /// \returns      Total number of handles (may be more than number copied)
+    size_t list_handles(j6_handle_t *handles, size_t len);
+
     /// Inform the process of an exited thread
     /// \args th  The thread which has exited
     /// \returns  True if this thread ending has ended the process
     bool thread_exited(thread *th);
 
     /// Get the handle for this process to refer to itself
-    inline j6_handle_t self_handle() const { return 1; }
+    inline j6_handle_t self_handle() const { return m_self_handle; }
 
     /// Get the process object that owns kernel threads and the
     /// kernel address space
@@ -95,6 +102,7 @@ private:
     // This constructor is called by create_kernel_process
     process(page_table *kpml4);
 
+    j6_handle_t m_self_handle;
     int32_t m_return_code;
 
     vm_space m_space;