Fix dlsym(3) to do breadth first search.

dlsym(3) with handle != RTLD_DEFAULT|RTLD_NEXT performs
  breadth first search through the dependency tree.

Bug: 16653281
Change-Id: I017a6975d1a62abb0218a7eb59ae4deba458e324

linker/linker.cpp

@@ -469,6 +469,10 @@ static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name,
     }
   }
 
+  TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd",
+             name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
+
+
   return NULL;
 }
 
@@ -585,18 +589,43 @@ done:
     return NULL;
 }
 
-/* This is used by dlsym(3).  It performs symbol lookup only within the
-   specified soinfo object and not in any of its dependencies.
+// Another soinfo list allocator to use in dlsym. We don't reuse
+// SoinfoListAllocator because it is write-protected most of the time.
+static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_list_allocator_rw;
+class SoinfoListAllocatorRW {
+ public:
+  static LinkedListEntry<soinfo>* alloc() {
+    return g_soinfo_list_allocator_rw.alloc();
+  }
 
-   TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says
-   that it should do a breadth first search through the dependency
-   tree. This agrees with the ELF spec (aka System V Application
-   Binary Interface) where in Chapter 5 it discuss resolving "Shared
-   Object Dependencies" in breadth first search order.
- */
-ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name, soinfo* caller) {
-    return soinfo_elf_lookup(si, elfhash(name), name,
-        caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal);
+  static void free(LinkedListEntry<soinfo>* ptr) {
+    g_soinfo_list_allocator_rw.free(ptr);
+  }
+};
+
+// This is used by dlsym(3).  It performs symbol lookup only within the
+// specified soinfo object and its dependencies in breadth first order.
+ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name, soinfo* caller) {
+  LinkedList<soinfo, SoinfoListAllocatorRW> visit_list;
+  visit_list.push_back(si);
+  soinfo* current_soinfo;
+  while ((current_soinfo = visit_list.pop_front()) != nullptr) {
+    ElfW(Sym)* result = soinfo_elf_lookup(current_soinfo, elfhash(name), name,
+        caller == current_soinfo ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal);
+
+    if (result != nullptr) {
+      *found = current_soinfo;
+      visit_list.clear();
+      return result;
+    }
+
+    current_soinfo->get_children().for_each([&](soinfo* child) {
+      visit_list.push_back(child);
+    });
+  }
+
+  visit_list.clear();
+  return nullptr;
 }
 
 /* This is used by dlsym(3) to performs a global symbol lookup. If the