Eo gdb: add a way to resolve Eo ids from GDB without a running process

Normally when debugging Eo with gdb you can just use any of the internal
eo functions to resolve the id to its internal pointer. However, when
loading a coredump you can't execute any code, not even the id resolve
code.

This change adds a gdb function that resolves the id to its pointer form
without executing any code in the process space. This plugin is
essentially the id resolve code written in python as a gdb function.

Usage:
 Print the pointer:
 (gdb) print $eo_resolve(obj)
 $1 = (_Eo_Object *) 0x5555559bbe70

 Use it directly (e.g. to print the class name):
 (gdb) $eo_resolve(obj)->klass->desc.name

This plugin requires that the coredump would be loaded with the exact
same libeo.so binary (or at least one that hasn't changed eo internals),
and that the debug symbols for libeo.so would be available for gdb to
use.

Note:
This feature is incomplete and only resolves IDs that are owned by the
main thread and in the main domain. This is not a big issue at the
moment, because almost all of our IDs are like that.

@feature

data/eo/eo_gdb.py

@@ -1,4 +1,104 @@
-# Implement eo_break that'll break on a macro/subid/whatever.
-
 import gdb
 
+"""
+All of this script relies heavily on Eo internals and will break if they
+change. Need to make sure this is always in sync.
+"""
+
+ptr_size = int(gdb.parse_and_eval('sizeof(void *)'))
+
+SHIFT_MID_TABLE_ID = 0x30
+MASK_MID_TABLE_ID = 0x7ff
+SHIFT_TABLE_ID = 0x25
+MASK_TABLE_ID = 0x7ff
+SHIFT_ENTRY_ID = 0x1a
+MASK_ENTRY_ID = 0x7ff
+MASK_GENERATIONS = 0x3ffffff
+MASK_OBJ_TAG = 0x4000000000000000
+
+if ptr_size == 4:
+    # 32 bits
+    BITS_MID_TABLE_ID = 5
+    BITS_TABLE_ID = 5
+    BITS_ENTRY_ID = 11
+    BITS_GENERATION_COUNTER = 6
+    BITS_DOMAIN = 2
+    BITS_CLASS = 1
+    REF_TAG_SHIFT = 30
+    SUPER_TAG_SHIFT = 31
+    DROPPED_TABLES = 0
+    DROPPED_ENTRIES = 4
+else:
+    # 64 bits
+    BITS_MID_TABLE_ID = 11
+    BITS_TABLE_ID = 11
+    BITS_ENTRY_ID = 11
+    BITS_GENERATION_COUNTER = 26
+    BITS_DOMAIN = 2
+    BITS_CLASS = 1
+    REF_TAG_SHIFT = 62
+    SUPER_TAG_SHIFT = 63
+    DROPPED_TABLES = 2
+    DROPPED_ENTRIES = 3
+
+# /* Shifts macros to manipulate the Eo id */
+SHIFT_DOMAIN = (BITS_MID_TABLE_ID + BITS_TABLE_ID +
+                BITS_ENTRY_ID + BITS_GENERATION_COUNTER)
+SHIFT_MID_TABLE_ID = (BITS_TABLE_ID +
+                      BITS_ENTRY_ID + BITS_GENERATION_COUNTER)
+SHIFT_TABLE_ID = (BITS_ENTRY_ID + BITS_GENERATION_COUNTER)
+SHIFT_ENTRY_ID = (BITS_GENERATION_COUNTER)
+
+# /* Maximum ranges */
+MAX_DOMAIN = (1 << BITS_DOMAIN)
+MAX_MID_TABLE_ID = (1 << BITS_MID_TABLE_ID)
+MAX_TABLE_ID = ((1 << BITS_TABLE_ID) - DROPPED_TABLES)
+MAX_ENTRY_ID = ((1 << BITS_ENTRY_ID) - DROPPED_ENTRIES)
+MAX_GENERATIONS = (1 << BITS_GENERATION_COUNTER)
+
+# /* Masks */
+MASK_DOMAIN = (MAX_DOMAIN - 1)
+MASK_MID_TABLE_ID = (MAX_MID_TABLE_ID - 1)
+MASK_TABLE_ID = ((1 << BITS_TABLE_ID) - 1)
+MASK_ENTRY_ID = ((1 << BITS_ENTRY_ID) - 1)
+MASK_GENERATIONS = (MAX_GENERATIONS - 1)
+MASK_OBJ_TAG = (1 << (REF_TAG_SHIFT))
+
+
+null_ptr = gdb.parse_and_eval('(_Eo_Object *) 0')
+
+
+class Eo_resolve(gdb.Function):
+    def __init__(self):
+        gdb.Function.__init__(self, 'eo_resolve')
+
+    def invoke(self, arg):
+        obj_id = int(arg)
+
+        mid_table_id = (obj_id >> SHIFT_MID_TABLE_ID) & MASK_MID_TABLE_ID
+        table_id = (obj_id >> SHIFT_TABLE_ID) & MASK_TABLE_ID
+        entry_id = (obj_id >> SHIFT_ENTRY_ID) & MASK_ENTRY_ID
+        tag_bit = (obj_id) & MASK_OBJ_TAG
+        generation = obj_id & MASK_GENERATIONS
+
+        if (obj_id == 0) or (tag_bit == 0):
+            gdb.write('Pointer is NULL or not a valid object.\n')
+            return null_ptr
+
+        entries = gdb.parse_and_eval('_eo_gdb_main_domain->tables[0]->' +
+                                     'eo_ids_tables[{0}]'.format(mid_table_id))
+
+        if int(entries) == 0:
+            gdb.write('Pointer is not a valid object.\n')
+            return null_ptr
+
+        entry = entries[table_id]['entries'][entry_id]
+
+        if (not entry['active']) or (int(entry['generation']) != generation):
+            gdb.write('Pointer is no longer active.\n')
+            return null_ptr
+
+        return entry['ptr']
+
+
+Eo_resolve()

src/lib/eo/eo.c

@@ -1881,6 +1881,11 @@ _eo_table_del_cb(void *in)
    _eo_free_ids_tables(data);
 }
 
+/* FIXME: Support other domains and tables, at the moment only the main
+ * domain and table.
+ * This is used by the gdb debug helper script */
+Eo_Id_Data *_eo_gdb_main_domain = NULL;
+
 EAPI Eina_Bool
 efl_object_init(void)
 {
@@ -1946,6 +1951,7 @@ efl_object_init(void)
 
    // specially force eoid data to be creanted so we can switch it to domain 0
    Eo_Id_Data *data = _eo_table_data_new(EFL_ID_DOMAIN_MAIN);
+   _eo_gdb_main_domain = data;
    if (!data)
      {
         EINA_LOG_ERR("Could not allocate main table data");