#87 add client symbol cache for gdb (#88)

Author: unknown321

decomp2dbg/clients/gdb/gdb_client.py

@@ -23,6 +23,7 @@ def __init__(self, gdb_client, name="decompiler", host="127.0.0.1", port=3662):
         self.symbol_mapper = SymbolMapper()
         self._is_pie = None
         self._lvar_bptr = None
+        self._symbol_cache = set()
 
     @property
     @lru_cache()
@@ -52,6 +53,13 @@ def decompiler_connected(self):
     def decompiler_disconnected(self):
         self.gdb_client.on_decompiler_disconnected(self.name)
 
+    def _cache(self, item):
+        if item in self._symbol_cache:
+            return False
+
+        self._symbol_cache.add(item)
+        return True
+
     def update_symbols(self):
         self.symbol_mapper.text_base_addr = self.text_base_addr
 
@@ -66,7 +74,10 @@ def update_symbols(self):
 
         # add symbols with native support if possible
         for addr, func in func_headers.items():
-            syms_to_add.append((func["name"], int(addr, 0), "function", func["size"]))
+            symbol = (func["name"], int(addr, 0), "function", func["size"])
+            new_entry = self._cache(symbol)
+            if new_entry:
+                syms_to_add.append(symbol)
             sym_name_set.add(func["name"])
 
         for addr, global_var in global_vars.items():
@@ -75,7 +86,10 @@ def update_symbols(self):
             if clean_name in sym_name_set:
                 continue
 
-            syms_to_add.append((clean_name, int(addr, 0), "object", global_var_size))
+            symbol = (clean_name, int(addr,0), "object", global_var_size)
+            new_entry = self._cache(symbol)
+            if new_entry:
+                syms_to_add.append(symbol)
 
         try:
             self.symbol_mapper.add_native_symbols(syms_to_add)

decomp2dbg/clients/gdb/gdb_client_test.py

@@ -0,0 +1,32 @@
+import unittest
+import sys
+from unittest.mock import Mock
+
+sys.modules["gdb"] = Mock()
+from decomp2dbg import GDBDecompilerClient
+
+
+# run with python -m unittest gdb_client_test.TestGDBDecompilerClient
+
+class TestGDBDecompilerClient(unittest.TestCase):
+    def setUp(self) -> None:
+        self._symbols = [
+            ("f1", 0x100, "function", 0x10),
+            ("f2", 0x200, "function", 0x10),
+            ("g1", 0x300, "object", 8),
+            ("g2", 0x400, "object", 8)
+        ]
+
+        self._c = GDBDecompilerClient(None)
+        for s in self._symbols:
+            self._c._cache(s)
+
+    def test_cache_new_entry(self):
+        entry = ("new symbol f3", 0x500, "function", 0x10)
+        is_new = self._c._cache(entry)
+        self.assertEqual(is_new, True, "entry is not not new")
+
+    def test_cache_old_entry(self):
+        existing = self._symbols[0]
+        is_new = self._c._cache(existing)
+        self.assertEqual(is_new, False, "entry is old, but cache func says it's new")

decomp2dbg/clients/gdb/symbol_mapper.py

@@ -62,6 +62,9 @@ def add_native_symbols(self, sym_info_list):
             return False
 
         # info("{:d} symbols will be added".format(len(sym_info_list)))
+        if len(sym_info_list) == 0:
+            return True
+
         self._delete_old_sym_files()
 
         # add each symbol into a mass symbol commit