fix: skip empty functions, relax jump-threading to handle multi-instr jmp stubs

cfg/builder.cpp

@@ -458,12 +458,19 @@ CFG CFGBuilder::build()
     set<addr_t> built;
     queue<addr_t> pending;
 
+    auto isEmpty = [](const Function& f) -> bool {
+        for (const auto& b : f.blocks)
+            if (!b.instructions.empty()) return false;
+        return true;
+    };
+
     auto process = [&](addr_t addr, const string& name)
     {
         if (built.count(addr)) return;
         built.insert(addr);
 
         auto func = buildFunction(addr, name);
+        if (isEmpty(func)) return;
         cfg.functions.push_back(func);
 
         for (const auto& b : func.blocks)
@@ -513,6 +520,7 @@ CFG CFGBuilder::build()
 
         built.insert(a);
         auto func = buildFunction(a, name);
+        if (isEmpty(func)) continue;
         cfg.functions.push_back(func);
 
         for (const auto& b : func.blocks)
@@ -616,8 +624,8 @@ static void jumpThread(CFG& cfg)
                 if (addr_to_func[t] != &func) continue;
 
                 BasicBlock* target = it->second;
-                if (target->instructions.size() == 1 &&
-                    target->instructions[0].mnemonic == "jmp" &&
+                if (!target->instructions.empty() &&
+                    target->instructions.back().mnemonic == "jmp" &&
                     target->successors.size() == 1)
                 {
                     addr_t redirect = target->successors[0];

tests/example1.exe.cfg

@@ -1,5 +1,5 @@
 {
-  "binary": "tests\\example1.exe",
+  "binary": "C:\\Dev\\Current\\BinaryHardening\\cfgrip\\tests\\example1.exe",
   "mode": "full",
   "arch": "x86-64",
   "format": "PE",
@@ -82571,12 +82571,6 @@
         }
       ]
     },
-    {
-      "address": "0x14000c9d0",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x140006544",
       "name": "",
@@ -95917,18 +95911,6 @@
         }
       ]
     },
-    {
-      "address": "0x140015200",
-      "name": "",
-      "blocks": [
-      ]
-    },
-    {
-      "address": "0x140011b00",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x140012358",
       "name": "",
@@ -114576,18 +114558,6 @@
         }
       ]
     },
-    {
-      "address": "0x14000b204",
-      "name": "",
-      "blocks": [
-      ]
-    },
-    {
-      "address": "0x14000ca74",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x14000a73c",
       "name": "",
@@ -135887,12 +135857,6 @@
         }
       ]
     },
-    {
-      "address": "0x1400075e8",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x140009dc4",
       "name": "",
@@ -144893,12 +144857,6 @@
         }
       ]
     },
-    {
-      "address": "0x140007650",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x140009f50",
       "name": "",
@@ -147615,12 +147573,6 @@
         }
       ]
     },
-    {
-      "address": "0x140004538",
-      "name": "",
-      "blocks": [
-      ]
-    },
     {
       "address": "0x14001a95c",
       "name": "",