Support global string initializer as part of constant expressions

When encoding strings with `StringEncOptGlobal` option, take into
account those appearing as part of global initializers of constant
expressions, used by global variables.

src/passes/strings-encoding/StringEncoding.cpp

@@ -123,18 +123,29 @@ bool StringEncoding::runOnBasicBlock(Module& M, Function& F, BasicBlock& BB,
           G = extractGlobalVariable(CE);
       }
 
-      if (!G)
-        continue;
+      auto IsInitializerConstantExpr = [](const GlobalVariable &G) {
+        return (!G.isExternallyInitialized() && G.hasInitializer()) &&
+               isa<ConstantExpr>(G.getInitializer());
+      };
+
+      Use *ActualOp = &Op;
+      bool MaybeStringInCEInitializer = false;
+      if (G && IsInitializerConstantExpr(*G)) {
+        // Is the global initializer part of a constant expression?
+        G = extractGlobalVariable(cast<ConstantExpr>(G->getInitializer()));
+        ActualOp = G->getSingleUndroppableUse();
+        MaybeStringInCEInitializer = true;
+      }
 
-      if (!isEligible(*G)) {
+      if (!G || !ActualOp)
         continue;
-      }
 
+      if (!isEligible(*G))
+        continue;
 
       auto* data = dyn_cast<ConstantDataSequential>(G->getInitializer());
-      if (data == nullptr) {
+      if (data == nullptr)
         continue;
-      }
 
       // Create a default option which skips the encoding
       auto encInfo = std::make_unique<StringEncodingOpt>(StringEncOptSkip());
@@ -150,11 +161,12 @@ bool StringEncoding::runOnBasicBlock(Module& M, Function& F, BasicBlock& BB,
         encInfo = std::make_unique<StringEncodingOpt>(userConfig.obfuscate_string(&M, &F, data->getAsCString().str()));
       }
 
-      if (isSkip(*encInfo)) {
+      if (isSkip(*encInfo) ||
+          (MaybeStringInCEInitializer &&
+           std::get_if<StringEncOptGlobal>(encInfo.get()) == nullptr))
         continue;
-      }
 
-      Changed |= process(BB, I, Op, *G, *data, *encInfo);
+      Changed |= process(BB, I, *ActualOp, *G, *data, *encInfo);
     }
   }
   return Changed;
@@ -171,12 +183,16 @@ PreservedAnalyses StringEncoding::run(Module &M, ModuleAnalysisManager &MAM) {
   RNG_ = M.createRNG(name());
   SDEBUG("[{}] Module: {}", name(), M.getSourceFileName());
 
-  for (Function &F : M) {
-    demotePHINode(F);
-    StringRef name = F.getName();
+  std::vector<Function *> FuncsToVisit;
+  for (Function &F : M)
+    FuncsToVisit.emplace_back(&F);
+
+  for (auto *F : FuncsToVisit) {
+    demotePHINode(*F);
+    StringRef name = F->getName();
     std::string demangled = demangle(name.str());
-    for (BasicBlock &BB : F) {
-      Changed |= runOnBasicBlock(M, F, BB, *userConfig);
+    for (BasicBlock &BB : *F) {
+      Changed |= runOnBasicBlock(M, *F, BB, *userConfig);
     }
   }
 

src/test/passes/strings-encoding/basic-aarch64-ce-init.ll

@@ -0,0 +1,20 @@
+; REQUIRES: aarch64-registered-target
+
+;     RUN: env OMVLL_CONFIG=%S/config_replace.py clang++ -fpass-plugin=%libOMVLL \
+;     RUN:         -target arm64-apple-ios  -fno-legacy-pass-manager -O1 -c %s -o - | strings | FileCheck %s
+;
+;     RUN: env OMVLL_CONFIG=%S/config_replace.py clang++ -fpass-plugin=%libOMVLL \
+;     RUN:         -target aarch64-linux-android  -fno-legacy-pass-manager -O1 -c %s -o - | strings | FileCheck %s
+;
+;     CHECK-NOT:     {{.*Hello.*}}
+
+@.hello = private constant [6 x i8] c"Hello\00"
+@str = global i8* getelementptr inbounds ([6 x i8], [6 x i8]* @.hello, i32 0, i32 0)
+
+define i32 @main() #0 {
+  %load = load i8*, i8** @str, align 8
+  %call = call i32 @puts(i8* %load)
+  ret i32 0
+}
+
+declare i32 @puts(i8*)

src/test/passes/strings-encoding/config_replace.py

@@ -5,6 +5,8 @@ class MyConfig(omvll.ObfuscationConfig):
     def __init__(self):
         super().__init__()
     def obfuscate_string(self, _, __, string: bytes):
+        if string.endswith(b"Hello"):
+            return omvll.StringEncOptGlobal()
         if string.endswith(b".cpp"):
             return omvll.StringEncOptGlobal()
         if string.endswith(b"Swift"):