userspace: fix kobj detection declared extern

If a variable is declared extern first, the name and type
information is stored in a special DW_DIE_variable which
is then referenced by the actual instances via the
tag DW_AT_specification.

We now place extern variable instances in an extern environment
and use this data to fetch the name/type of the instances,
which do not have it (which is why they were being skipped).

As it turns out, the gross hack for the system workqueue was
due to this problem because of the extern declaration in
kernel.h.

Fixes: #6992

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

scripts/elf_helper.py

@@ -36,6 +36,7 @@ thread_counter = 0
 
 # Global type environment. Populated by pass 1.
 type_env = {}
+extern_env = {}
 kobjects = {}
 subsystems = {}
 
@@ -210,15 +211,32 @@ class AggregateType:
 
 # --- helper functions for getting data from DIEs ---
 
+def die_get_spec(die):
+    if 'DW_AT_specification' not in die.attributes:
+        return None
+
+    spec_val = die.attributes["DW_AT_specification"].value
+
+    # offset of the DW_TAG_variable for the extern declaration
+    offset = spec_val + die.cu.cu_offset
+
+    return extern_env.get(offset)
+
+
 def die_get_name(die):
     if 'DW_AT_name' not in die.attributes:
-        return None
+        die = die_get_spec(die)
+        if not die:
+            return None
+
     return die.attributes["DW_AT_name"].value.decode("utf-8")
 
 
 def die_get_type_offset(die):
     if 'DW_AT_type' not in die.attributes:
-        return 0
+        die = die_get_spec(die)
+        if not die:
+            return None
 
     return die.attributes["DW_AT_type"].value + die.cu.cu_offset
 
@@ -381,9 +399,6 @@ class ElfHelper:
         # all variables
         all_objs = {}
 
-        # Gross hack, see below
-        work_q_found = False
-
         for die in variables:
             name = die_get_name(die)
             if not name:
@@ -397,49 +412,42 @@ class ElfHelper:
                 continue
 
             if "DW_AT_declaration" in die.attributes:
-                # FIXME: why does k_sys_work_q not resolve an address in the
-                # DWARF data??? Every single instance it finds is an extern
-                # definition but not the actual instance in system_work_q.c
-                # Is there something weird about how lib-y stuff is linked?
-                if name == "k_sys_work_q" and not work_q_found and \
-                   name in syms:
-                    addr = syms[name]
-                    work_q_found = True
+                # Extern declaration, only used indirectly
+                extern_env[die.offset] = die
+                continue
+
+            if "DW_AT_location" not in die.attributes:
+                self.debug_die(
+                    die,
+                    "No location information for object '%s'; possibly"
+                    " stack allocated" % name)
+                continue
+
+            loc = die.attributes["DW_AT_location"]
+            if loc.form != "DW_FORM_exprloc" and \
+               loc.form != "DW_FORM_block1":
+                self.debug_die(
+                    die,
+                    "kernel object '%s' unexpected location format" %
+                    name)
+                continue
+
+            opcode = loc.value[0]
+            if opcode != DW_OP_addr:
+
+                # Check if frame pointer offset DW_OP_fbreg
+                if opcode == DW_OP_fbreg:
+                    self.debug_die(die, "kernel object '%s' found on stack" %
+                              name)
                 else:
-                    continue
-            else:
-                if "DW_AT_location" not in die.attributes:
                     self.debug_die(
                         die,
-                        "No location information for object '%s'; possibly"
-                        " stack allocated" % name)
-                    continue
+                        "kernel object '%s' unexpected exprloc opcode %s" %
+                        (name, hex(opcode)))
+                continue
 
-                loc = die.attributes["DW_AT_location"]
-                if loc.form != "DW_FORM_exprloc" and \
-                   loc.form != "DW_FORM_block1":
-                    self.debug_die(
-                        die,
-                        "kernel object '%s' unexpected location format" %
-                        name)
-                    continue
-
-                opcode = loc.value[0]
-                if opcode != DW_OP_addr:
-
-                    # Check if frame pointer offset DW_OP_fbreg
-                    if opcode == DW_OP_fbreg:
-                        self.debug_die(die, "kernel object '%s' found on stack" %
-                                  name)
-                    else:
-                        self.debug_die(
-                            die,
-                            "kernel object '%s' unexpected exprloc opcode %s" %
-                            (name, hex(opcode)))
-                    continue
-
-                addr = (loc.value[1] | (loc.value[2] << 8) |
-                        (loc.value[3] << 16) | (loc.value[4] << 24))
+            addr = (loc.value[1] | (loc.value[2] << 8) |
+                    (loc.value[3] << 16) | (loc.value[4] << 24))
 
             if addr == 0:
                 # Never linked; gc-sections deleted it

tests/kernel/mem_protect/obj_validation/src/main.c

@@ -10,6 +10,11 @@
 
 #define SEM_ARRAY_SIZE	16
 
+/* Show that extern declarations don't interfere with detecting kernel
+ * objects, this was at one point a problem.
+ */
+extern struct k_sem sem1;
+
 static __kernel struct k_sem semarray[SEM_ARRAY_SIZE];
 static struct k_sem *dyn_sem[SEM_ARRAY_SIZE];