DynamicLoader: Resolve missing weak absolute symbols to null

Weak symbols can be left unresolved, and code is supposed to check if
they're null at runtime before using them. Handle them appropriately
instead of refusing to load.

Userland/Libraries/LibELF/DynamicLoader.cpp

@@ -520,7 +520,7 @@ void DynamicLoader::load_program_headers()
 
 DynamicLoader::RelocationResult DynamicLoader::do_direct_relocation(DynamicObject::Relocation const& relocation,
     Optional<DynamicLoader::CachedLookupResult>& cached_result,
-    [[maybe_unused]] ShouldInitializeWeak should_initialize_weak,
+    ShouldInitializeWeak should_initialize_weak,
     ShouldCallIfuncResolver should_call_ifunc_resolver)
 {
     FlatPtr* patch_ptr = nullptr;
@@ -569,21 +569,26 @@ DynamicLoader::RelocationResult DynamicLoader::do_direct_relocation(DynamicObjec
     case ABSOLUTE: {
         auto symbol = relocation.symbol();
         auto res = lookup_symbol(symbol);
+        VirtualAddress symbol_address;
         if (!res.has_value()) {
-            if (symbol.bind() == STB_WEAK)
-                return RelocationResult::ResolveLater;
-            dbgln("ERROR: symbol not found: {}.", symbol.name());
-            return RelocationResult::Failed;
+            if (symbol.bind() == STB_WEAK) {
+                if (should_initialize_weak == ShouldInitializeWeak::No)
+                    return RelocationResult::ResolveLater;
+            } else {
+                dbgln("ERROR: symbol not found: {}.", symbol.name());
+                return RelocationResult::Failed;
+            }
+            symbol_address = VirtualAddress { (FlatPtr)0 };
+        } else {
+            if (res.value().type == STT_GNU_IFUNC && should_call_ifunc_resolver == ShouldCallIfuncResolver::No)
+                return RelocationResult::CallIfuncResolver;
+            symbol_address = res.value().address;
         }
-        if (res.value().type == STT_GNU_IFUNC && should_call_ifunc_resolver == ShouldCallIfuncResolver::No)
-            return RelocationResult::CallIfuncResolver;
-
-        auto symbol_address = res.value().address;
         if (relocation.addend_used())
             *patch_ptr = symbol_address.get() + relocation.addend();
         else
             *patch_ptr += symbol_address.get();
-        if (res.value().type == STT_GNU_IFUNC)
+        if (res.has_value() && res.value().type == STT_GNU_IFUNC)
             *patch_ptr = call_ifunc_resolver(VirtualAddress { *patch_ptr }).get();
         break;
     }