Merge "Improve detection of already loaded libraries"

linker/dlfcn.cpp

@@ -225,78 +225,26 @@ static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 0 };
 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 0 };
 #endif
 
+// Defined as global because we do not yet have access
+// to synchronization functions __cxa_guard_* needed
+// to define statics inside functions.
+static soinfo __libdl_info;
+
 // This is used by the dynamic linker. Every process gets these symbols for free.
-soinfo libdl_info = {
+soinfo* get_libdl_info() {
-    "libdl.so",
+  if (__libdl_info.name[0] == '\0') {
+    // initialize
+    strncpy(__libdl_info.name, "libdl.so", sizeof(__libdl_info.name));
+    __libdl_info.flags = FLAG_LINKED | FLAG_NEW_SOINFO;
+    __libdl_info.strtab = ANDROID_LIBDL_STRTAB;
+    __libdl_info.symtab = g_libdl_symtab;
+    __libdl_info.nbucket = sizeof(g_libdl_buckets)/sizeof(unsigned);
+    __libdl_info.nchain = sizeof(g_libdl_chains)/sizeof(unsigned);
+    __libdl_info.bucket = g_libdl_buckets;
+    __libdl_info.chain = g_libdl_chains;
+    __libdl_info.has_DT_SYMBOLIC = true;
+  }
 
-    .phdr = 0,
+  return &__libdl_info;
-    .phnum = 0,
+}
-    .entry = 0,
-    .base = 0,
-    .size = 0,
 
-#if !defined(__LP64__)
-    .unused1 = 0,
-#endif
-
-    .dynamic = 0,
-
-#if !defined(__LP64__)
-    .unused2 = 0, .unused3 = 0,
-#endif
-
-    .next = 0,
-
-    .flags = FLAG_LINKED,
-
-    .strtab = ANDROID_LIBDL_STRTAB,
-    .symtab = g_libdl_symtab,
-
-    .nbucket = sizeof(g_libdl_buckets)/sizeof(unsigned),
-    .nchain = sizeof(g_libdl_chains)/sizeof(unsigned),
-    .bucket = g_libdl_buckets,
-    .chain = g_libdl_chains,
-
-#if defined(USE_RELA)
-    .plt_rela = 0,
-    .plt_rela_count = 0,
-    .rela = 0,
-    .rela_count = 0,
-#else
-    .plt_got = 0,
-    .plt_rel = 0,
-    .plt_rel_count = 0,
-    .rel = 0,
-    .rel_count = 0,
-#endif
-
-    .preinit_array = 0,
-    .preinit_array_count = 0,
-
-    .init_array = 0,
-    .init_array_count = 0,
-
-    .fini_array = 0,
-    .fini_array_count = 0,
-
-    .init_func = 0,
-    .fini_func = 0,
-
-#if defined(__arm__)
-    .ARM_exidx = 0,
-    .ARM_exidx_count = 0,
-#elif defined(__mips__)
-    .mips_symtabno = 0,
-    .mips_local_gotno = 0,
-    .mips_gotsym = 0,
-#endif
-
-    .ref_count = 0,
-    { .l_addr = 0, .l_name = 0, .l_ld = 0, .l_next = 0, .l_prev = 0, },
-    .constructors_called = false,
-    .load_bias = 0,
-#if !defined(__LP64__)
-    .has_text_relocations = false,
-#endif
-    .has_DT_SYMBOLIC = true,
-};

linker/linked_list.h

@@ -0,0 +1,75 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __LINKED_LIST_H
+#define __LINKED_LIST_H
+
+#include "private/bionic_macros.h"
+
+template<typename T>
+struct LinkedListEntry {
+  LinkedListEntry<T>* next;
+  T* element;
+};
+
+/*
+ * Represents linked list of objects of type T
+ */
+template<typename T, typename Allocator>
+class LinkedList {
+ public:
+  LinkedList() : head_(nullptr) {}
+
+  void push_front(T* const element) {
+    LinkedListEntry<T>* new_entry = Allocator::alloc();
+    new_entry->next = head_;
+    new_entry->element = element;
+    head_ = new_entry;
+  }
+
+  void clear() {
+    while (head_ != nullptr) {
+      LinkedListEntry<T>* p = head_;
+      head_ = head_->next;
+      Allocator::free(p);
+    }
+  }
+
+  template<typename F>
+  void for_each(F&& action) {
+    for (LinkedListEntry<T>* e = head_; e != nullptr; e = e->next) {
+      if (e->element != nullptr) {
+        action(e->element);
+      }
+    }
+  }
+
+  template<typename F>
+  void remove_if(F&& predicate) {
+    LinkedListEntry<T>* e = head_;
+    for (LinkedListEntry<T>* e = head_; e != nullptr; e = e->next) {
+      if (e->element != nullptr && predicate(e->element)) {
+        e->element = nullptr;
+      }
+    }
+  }
+
+ private:
+  LinkedListEntry<T>* head_;
+  DISALLOW_COPY_AND_ASSIGN(LinkedList);
+};
+
+#endif // __LINKED_LIST_H

linker/linker.cpp

@@ -68,13 +68,11 @@
 static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo);
 static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
 
-// We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous
-// maps, each a single page in size. The pages are broken up into as many struct soinfo
-// objects as will fit.
 static LinkerAllocator<soinfo> g_soinfo_allocator;
+static LinkerAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator;
 
-static soinfo* solist = &libdl_info;
+static soinfo* solist;
-static soinfo* sonext = &libdl_info;
+static soinfo* sonext;
 static soinfo* somain; /* main process, always the one after libdl_info */
 
 static const char* const kDefaultLdPaths[] = {
@@ -263,7 +261,20 @@ void notify_gdb_of_libraries() {
   rtld_db_dlactivity();
 }
 
-static soinfo* soinfo_alloc(const char* name) {
+LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() {
+  return g_soinfo_links_allocator.alloc();
+}
+
+void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) {
+  g_soinfo_links_allocator.free(entry);
+}
+
+static void protect_data(int protection) {
+  g_soinfo_allocator.protect_all(protection);
+  g_soinfo_links_allocator.protect_all(protection);
+}
+
+static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) {
   if (strlen(name) >= SOINFO_NAME_LEN) {
     DL_ERR("library name \"%s\" too long", name);
     return NULL;
@@ -274,6 +285,13 @@ static soinfo* soinfo_alloc(const char* name) {
   // Initialize the new element.
   memset(si, 0, sizeof(soinfo));
   strlcpy(si->name, name, sizeof(si->name));
+  si->flags = FLAG_NEW_SOINFO;
+
+  if (file_stat != NULL) {
+    si->set_st_dev(file_stat->st_dev);
+    si->set_st_ino(file_stat->st_ino);
+  }
+
   sonext->next = si;
   sonext = si;
 
@@ -286,6 +304,10 @@ static void soinfo_free(soinfo* si) {
         return;
     }
 
+    if (si->base != 0 && si->size != 0) {
+      munmap(reinterpret_cast<void*>(si->base), si->size);
+    }
+
     soinfo *prev = NULL, *trav;
 
     TRACE("name %s: freeing soinfo @ %p", si->name, si);
@@ -301,6 +323,9 @@ static void soinfo_free(soinfo* si) {
         return;
     }
 
+    // clear links to/from si
+    si->remove_all_links();
+
     /* prev will never be NULL, because the first entry in solist is
        always the static libdl_info.
     */
@@ -651,25 +676,52 @@ static soinfo* load_library(const char* name, const android_dlextinfo* extinfo)
         return NULL;
     }
 
-    // Read the ELF header and load the segments.
     ElfReader elf_reader(name, fd);
+
+    struct stat file_stat;
+    if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
+      DL_ERR("unable to stat file for the library %s: %s", name, strerror(errno));
+      return NULL;
+    }
+
+    // Check for symlink and other situations where
+    // file can have different names.
+    for (soinfo* si = solist; si != NULL; si = si->next) {
+      if (si->get_st_dev() != 0 &&
+          si->get_st_ino() != 0 &&
+          si->get_st_dev() == file_stat.st_dev &&
+          si->get_st_ino() == file_stat.st_ino) {
+        TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
+        return si;
+      }
+    }
+
+    // Read the ELF header and load the segments.
     if (!elf_reader.Load(extinfo)) {
         return NULL;
     }
 
     const char* bname = strrchr(name, '/');
-    soinfo* si = soinfo_alloc(bname ? bname + 1 : name);
+    soinfo* si = soinfo_alloc(bname ? bname + 1 : name, &file_stat);
     if (si == NULL) {
         return NULL;
     }
     si->base = elf_reader.load_start();
     si->size = elf_reader.load_size();
     si->load_bias = elf_reader.load_bias();
-    si->flags = 0;
-    si->entry = 0;
-    si->dynamic = NULL;
     si->phnum = elf_reader.phdr_count();
     si->phdr = elf_reader.loaded_phdr();
+
+    // At this point we know that whatever is loaded @ base is a valid ELF
+    // shared library whose segments are properly mapped in.
+    TRACE("[ find_library_internal base=%p size=%zu name='%s' ]",
+          reinterpret_cast<void*>(si->base), si->size, si->name);
+
+    if (!soinfo_link_image(si, extinfo)) {
+      soinfo_free(si);
+      return NULL;
+    }
+
     return si;
 }
 
@@ -703,23 +755,7 @@ static soinfo* find_library_internal(const char* name, const android_dlextinfo*
   }
 
   TRACE("[ '%s' has not been loaded yet.  Locating...]", name);
-  si = load_library(name, extinfo);
+  return load_library(name, extinfo);
-  if (si == NULL) {
-    return NULL;
-  }
-
-  // At this point we know that whatever is loaded @ base is a valid ELF
-  // shared library whose segments are properly mapped in.
-  TRACE("[ find_library_internal base=%p size=%zu name='%s' ]",
-        reinterpret_cast<void*>(si->base), si->size, si->name);
-
-  if (!soinfo_link_image(si, extinfo)) {
-    munmap(reinterpret_cast<void*>(si->base), si->size);
-    soinfo_free(si);
-    return NULL;
-  }
-
-  return si;
 }
 
 static soinfo* find_library(const char* name, const android_dlextinfo* extinfo) {
@@ -735,15 +771,21 @@ static int soinfo_unload(soinfo* si) {
     TRACE("unloading '%s'", si->name);
     si->CallDestructors();
 
-    for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
+    if ((si->flags | FLAG_NEW_SOINFO) != 0) {
-      if (d->d_tag == DT_NEEDED) {
+      si->get_children().for_each([&] (soinfo* child) {
-        const char* library_name = si->strtab + d->d_un.d_val;
+        TRACE("%s needs to unload %s", si->name, child->name);
-        TRACE("%s needs to unload %s", si->name, library_name);
+        soinfo_unload(child);
-        soinfo_unload(find_loaded_library(library_name));
+      });
+    } else {
+      for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
+        if (d->d_tag == DT_NEEDED) {
+          const char* library_name = si->strtab + d->d_un.d_val;
+          TRACE("%s needs to unload %s", si->name, library_name);
+          soinfo_unload(find_loaded_library(library_name));
+        }
       }
     }
 
-    munmap(reinterpret_cast<void*>(si->base), si->size);
     notify_gdb_of_unload(si);
     si->ref_count = 0;
     soinfo_free(si);
@@ -773,19 +815,20 @@ soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo)
     DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags);
     return NULL;
   }
-  g_soinfo_allocator.protect_all(PROT_READ | PROT_WRITE);
+  protect_data(PROT_READ | PROT_WRITE);
   soinfo* si = find_library(name, extinfo);
   if (si != NULL) {
     si->CallConstructors();
+    somain->add_child(si);
   }
-  g_soinfo_allocator.protect_all(PROT_READ);
+  protect_data(PROT_READ);
   return si;
 }
 
 int do_dlclose(soinfo* si) {
-  g_soinfo_allocator.protect_all(PROT_READ | PROT_WRITE);
+  protect_data(PROT_READ | PROT_WRITE);
   int result = soinfo_unload(si);
-  g_soinfo_allocator.protect_all(PROT_READ);
+  protect_data(PROT_READ);
   return result;
 }
 
@@ -1333,7 +1376,7 @@ void soinfo::CallFunction(const char* function_name __unused, linker_function_t
 
   // The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
   // are still writable. This happens with our debug malloc (see http://b/7941716).
-  g_soinfo_allocator.protect_all(PROT_READ | PROT_WRITE);
+  protect_data(PROT_READ | PROT_WRITE);
 }
 
 void soinfo::CallPreInitConstructors() {
@@ -1365,15 +1408,9 @@ void soinfo::CallConstructors() {
           name, preinit_array_count);
   }
 
-  if (dynamic != NULL) {
+  get_children().for_each([] (soinfo* si) {
-    for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
+    si->CallConstructors();
-      if (d->d_tag == DT_NEEDED) {
+  });
-        const char* library_name = strtab + d->d_un.d_val;
-        TRACE("\"%s\": calling constructors in DT_NEEDED \"%s\"", name, library_name);
-        find_loaded_library(library_name)->CallConstructors();
-      }
-    }
-  }
 
   TRACE("\"%s\": calling constructors", name);
 
@@ -1392,6 +1429,82 @@ void soinfo::CallDestructors() {
   CallFunction("DT_FINI", fini_func);
 }
 
+void soinfo::add_child(soinfo* child) {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return;
+  }
+
+  this->children.push_front(child);
+  child->parents.push_front(this);
+}
+
+void soinfo::remove_all_links() {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return;
+  }
+
+  // 1. Untie connected soinfos from 'this'.
+  children.for_each([&] (soinfo* child) {
+    child->parents.remove_if([&] (const soinfo* parent) {
+      return parent == this;
+    });
+  });
+
+  parents.for_each([&] (soinfo* parent) {
+    parent->children.for_each([&] (const soinfo* child) {
+      return child == this;
+    });
+  });
+
+  // 2. Once everything untied - clear local lists.
+  parents.clear();
+  children.clear();
+}
+
+void soinfo::set_st_dev(dev_t dev) {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return;
+  }
+
+  st_dev = dev;
+}
+
+void soinfo::set_st_ino(ino_t ino) {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return;
+  }
+
+  st_ino = ino;
+}
+
+dev_t soinfo::get_st_dev() {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return 0;
+  }
+
+  return st_dev;
+};
+
+ino_t soinfo::get_st_ino() {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return 0;
+  }
+
+  return st_ino;
+}
+
+// This is a return on get_children() in case
+// 'this->flags' does not have FLAG_NEW_SOINFO set.
+static soinfo::soinfo_list_t g_empty_list;
+
+soinfo::soinfo_list_t& soinfo::get_children() {
+  if ((this->flags & FLAG_NEW_SOINFO) == 0) {
+    return g_empty_list;
+  }
+
+  return this->children;
+}
+
 /* Force any of the closed stdin, stdout and stderr to be associated with
    /dev/null. */
 static int nullify_closed_stdio() {
@@ -1715,6 +1828,8 @@ static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) {
                        library_name, si->name, tmp_err_buf);
                 return false;
             }
+
+            si->add_child(lsi);
             *pneeded++ = lsi;
         }
     }
@@ -1824,19 +1939,52 @@ static void add_vdso(KernelArgumentBlock& args __unused) {
     return;
   }
 
-  soinfo* si = soinfo_alloc("[vdso]");
+  soinfo* si = soinfo_alloc("[vdso]", NULL);
 
   si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
   si->phnum = ehdr_vdso->e_phnum;
   si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
   si->size = phdr_table_get_load_size(si->phdr, si->phnum);
-  si->flags = 0;
   si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
 
   soinfo_link_image(si, NULL);
 #endif
 }
 
+/*
+ * This is linker soinfo for GDB. See details below.
+ */
+static soinfo linker_soinfo_for_gdb;
+
+/* gdb expects the linker to be in the debug shared object list.
+ * Without this, gdb has trouble locating the linker's ".text"
+ * and ".plt" sections. Gdb could also potentially use this to
+ * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
+ * Don't use soinfo_alloc(), because the linker shouldn't
+ * be on the soinfo list.
+ */
+static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
+#if defined(__LP64__)
+  strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name));
+#else
+  strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name));
+#endif
+  linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO;
+  linker_soinfo_for_gdb.base = linker_base;
+
+  /*
+   * Set the dynamic field in the link map otherwise gdb will complain with
+   * the following:
+   *   warning: .dynamic section for "/system/bin/linker" is not at the
+   *   expected address (wrong library or version mismatch?)
+   */
+  ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
+  ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
+  phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
+                                 &linker_soinfo_for_gdb.dynamic, NULL, NULL);
+  insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
+}
+
 /*
  * This code is called after the linker has linked itself and
  * fixed it's own GOT. It is safe to make references to externs
@@ -1886,12 +2034,13 @@ static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(
 
     // Linker does not call constructors for its own
     // global variables so we need to initialize
-    // the allocator explicitly.
+    // the allocators explicitly.
     g_soinfo_allocator.init();
+    g_soinfo_links_allocator.init();
 
     INFO("[ android linker & debugger ]");
 
-    soinfo* si = soinfo_alloc(args.argv[0]);
+    soinfo* si = soinfo_alloc(args.argv[0], NULL);
     if (si == NULL) {
         exit(EXIT_FAILURE);
     }
@@ -1908,35 +2057,7 @@ static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(
     _r_debug.r_map = map;
     r_debug_tail = map;
 
-    /* gdb expects the linker to be in the debug shared object list.
+    init_linker_info_for_gdb(linker_base);
-     * Without this, gdb has trouble locating the linker's ".text"
-     * and ".plt" sections. Gdb could also potentially use this to
-     * relocate the offset of our exported 'rtld_db_dlactivity' symbol.
-     * Don't use soinfo_alloc(), because the linker shouldn't
-     * be on the soinfo list.
-     */
-    {
-        static soinfo linker_soinfo;
-#if defined(__LP64__)
-        strlcpy(linker_soinfo.name, "/system/bin/linker64", sizeof(linker_soinfo.name));
-#else
-        strlcpy(linker_soinfo.name, "/system/bin/linker", sizeof(linker_soinfo.name));
-#endif
-        linker_soinfo.flags = 0;
-        linker_soinfo.base = linker_base;
-
-        /*
-         * Set the dynamic field in the link map otherwise gdb will complain with
-         * the following:
-         *   warning: .dynamic section for "/system/bin/linker" is not at the
-         *   expected address (wrong library or version mismatch?)
-         */
-        ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
-        ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
-        phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
-                                       &linker_soinfo.dynamic, NULL, NULL);
-        insert_soinfo_into_debug_map(&linker_soinfo);
-    }
 
     // Extract information passed from the kernel.
     si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
@@ -2071,6 +2192,10 @@ static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
  * function, or other GOT reference will generate a segfault.
  */
 extern "C" ElfW(Addr) __linker_init(void* raw_args) {
+  // Initialize static variables.
+  solist = get_libdl_info();
+  sonext = get_libdl_info();
+
   KernelArgumentBlock args(raw_args);
 
   ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
@@ -2106,7 +2231,7 @@ extern "C" ElfW(Addr) __linker_init(void* raw_args) {
   args.abort_message_ptr = &g_abort_message;
   ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
 
-  g_soinfo_allocator.protect_all(PROT_READ);
+  protect_data(PROT_READ);
 
   // Return the address that the calling assembly stub should jump to.
   return start_address;

linker/linker.h

@@ -33,8 +33,10 @@
 #include <link.h>
 #include <unistd.h>
 #include <android/dlext.h>
+#include <sys/stat.h>
 
 #include "private/libc_logging.h"
+#include "linked_list.h"
 
 #define DL_ERR(fmt, x...) \
     do { \
@@ -84,6 +86,7 @@
 #define FLAG_LINKED     0x00000001
 #define FLAG_EXE        0x00000004 // The main executable
 #define FLAG_LINKER     0x00000010 // The linker itself
+#define FLAG_NEW_SOINFO 0x40000000 // new soinfo format
 
 #define SOINFO_NAME_LEN 128
 
@@ -94,7 +97,20 @@ typedef void (*linker_function_t)();
 #define USE_RELA 1
 #endif
 
+struct soinfo;
+
+class SoinfoListAllocator {
+public:
+  static LinkedListEntry<soinfo>* alloc();
+  static void free(LinkedListEntry<soinfo>* entry);
+private:
+  // unconstructable
+  DISALLOW_IMPLICIT_CONSTRUCTORS(SoinfoListAllocator);
+};
+
 struct soinfo {
+ public:
+  typedef LinkedList<soinfo, SoinfoListAllocator> soinfo_list_t;
  public:
   char name[SOINFO_NAME_LEN];
   const ElfW(Phdr)* phdr;
@@ -179,17 +195,39 @@ struct soinfo {
   bool has_text_relocations;
 #endif
   bool has_DT_SYMBOLIC;
-
   void CallConstructors();
   void CallDestructors();
   void CallPreInitConstructors();
 
+  void add_child(soinfo* child);
+  void remove_all_links();
+
+  void set_st_dev(dev_t st_dev);
+  void set_st_ino(ino_t st_ino);
+  ino_t get_st_ino();
+  dev_t get_st_dev();
+
+  soinfo_list_t& get_children();
+
  private:
   void CallArray(const char* array_name, linker_function_t* functions, size_t count, bool reverse);
   void CallFunction(const char* function_name, linker_function_t function);
+
+ private:
+  // This part of the structure is only available
+  // when FLAG_NEW_SOINFO is set in this->flags.
+  unsigned int version;
+
+  dev_t st_dev;
+  ino_t st_ino;
+
+  // dependency graph
+  soinfo_list_t children;
+  soinfo_list_t parents;
+
 };
 
-extern soinfo libdl_info;
+extern soinfo* get_libdl_info();
 
 void do_android_get_LD_LIBRARY_PATH(char*, size_t);
 void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path);

linker/linker_allocator.cpp

@@ -55,8 +55,7 @@ void* LinkerBlockAllocator::alloc() {
     free_block_list_ = block_info->next_block;
   }
 
-  block_info->next_block = nullptr;
+  memset(block_info, 0, block_size_);
-  block_info->num_free_blocks = 0;
 
   return block_info;
 }
@@ -78,6 +77,8 @@ void LinkerBlockAllocator::free(void* block) {
     abort();
   }
 
+  memset(block, 0, block_size_);
+
   FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
 
   block_info->next_block = free_block_list_;
@@ -100,6 +101,7 @@ void LinkerBlockAllocator::create_new_page() {
   if (page == MAP_FAILED) {
     abort(); // oom
   }
+  memset(page, 0, PAGE_SIZE);
 
   FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
   first_block->next_block = free_block_list_;

linker/linker_allocator.h

@@ -51,6 +51,8 @@ class LinkerBlockAllocator {
 };
 
 /*
+ * We can't use malloc(3) in the dynamic linker.
+ *
  * A simple allocator for the dynamic linker. An allocator allocates instances
  * of a single fixed-size type. Allocations are backed by page-sized private
  * anonymous mmaps.

linker/tests/Android.mk

@@ -30,6 +30,7 @@ LOCAL_CFLAGS += -g -Wall -Wextra -Werror -std=gnu++11
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/../../libc/
 
 LOCAL_SRC_FILES := \
+  linked_list_test.cpp \
   linker_allocator_test.cpp \
   ../linker_allocator.cpp
 

linker/tests/linked_list_test.cpp

@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdlib.h>
+#include <string>
+#include <sstream>
+
+#include <gtest/gtest.h>
+
+#include "../linked_list.h"
+
+namespace {
+
+bool alloc_called = false;
+bool free_called = false;
+
+class LinkedListTestAllocator {
+ public:
+  typedef LinkedListEntry<const char> entry_t;
+
+  static entry_t* alloc() {
+    alloc_called = true;
+    return reinterpret_cast<entry_t*>(::malloc(sizeof(entry_t)));
+  }
+
+  static void free(entry_t* p) {
+    free_called = true;
+    ::free(p);
+  }
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(LinkedListTestAllocator);
+};
+
+typedef LinkedList<const char, LinkedListTestAllocator> test_list_t;
+
+std::string test_list_to_string(test_list_t& list) {
+  std::stringstream ss;
+  list.for_each([&] (const char* c) {
+    ss << c;
+  });
+
+  return ss.str();
+}
+
+};
+
+TEST(linked_list, simple) {
+  alloc_called = free_called = false;
+  test_list_t list;
+  ASSERT_EQ("", test_list_to_string(list));
+  ASSERT_TRUE(!alloc_called);
+  ASSERT_TRUE(!free_called);
+  list.push_front("a");
+  ASSERT_TRUE(alloc_called);
+  ASSERT_TRUE(!free_called);
+  ASSERT_EQ("a", test_list_to_string(list));
+  list.push_front("b");
+  ASSERT_EQ("ba", test_list_to_string(list));
+  list.push_front("c");
+  list.push_front("d");
+  ASSERT_EQ("dcba", test_list_to_string(list));
+  ASSERT_TRUE(alloc_called);
+  ASSERT_TRUE(!free_called);
+  alloc_called = free_called = false;
+  list.remove_if([] (const char* c) {
+    return *c == 'c';
+  });
+
+  ASSERT_TRUE(!alloc_called);
+  ASSERT_TRUE(!free_called);
+
+  ASSERT_EQ("dba", test_list_to_string(list));
+  alloc_called = free_called = false;
+  list.remove_if([] (const char* c) {
+    return *c == '2';
+  });
+  ASSERT_TRUE(!alloc_called);
+  ASSERT_TRUE(!free_called);
+  ASSERT_EQ("dba", test_list_to_string(list));
+  list.clear();
+  ASSERT_TRUE(!alloc_called);
+  ASSERT_TRUE(free_called);
+  ASSERT_EQ("", test_list_to_string(list));
+}

tests/Android.mk

@@ -227,6 +227,19 @@ $(libdlext_sym): $(libdlext_origin)
 ALL_MODULES := \
   $(ALL_MODULES) $(libdlext_sym)
 
+ifneq ($(TARGET_2ND_ARCH),)
+# link 64 bit .so
+libdlext_origin := $(TARGET_OUT)/lib64/libdlext_test.so
+libdlext_sym := $(subst libdlext_test,libdlext_test_v2,$(libdlext_origin))
+$(libdlext_sym): $(libdlext_origin)
+	@echo "Symlink: $@ -> $(notdir $<)"
+	@mkdir -p $(dir $@)
+	$(hide) ln -sf $(notdir $<) $@
+
+ALL_MODULES := \
+  $(ALL_MODULES) $(libdlext_sym)
+endif
+
 libdlext_test_norelro_src_files := \
     dlext_test_library.cpp \