linker/linker_soinfo.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#pragma once

#include <link.h>

#include <string>

#include "linker_namespaces.h"

#define FLAG_LINKED           0x00000001
#define FLAG_EXE              0x00000004 // The main executable
#define FLAG_LINKER           0x00000010 // The linker itself
#define FLAG_GNU_HASH         0x00000040 // uses gnu hash
#define FLAG_MAPPED_BY_CALLER 0x00000080 // the map is reserved by the caller
                                         // and should not be unmapped
#define FLAG_IMAGE_LINKED     0x00000100 // Is image linked - this is a guard on link_image.
                                         // The difference between this flag and
                                         // FLAG_LINKED is that FLAG_LINKED
                                         // means is set when load_group is
                                         // successfully loaded whereas this
                                         // flag is set to avoid linking image
                                         // when link_image called for the
                                         // second time. This situation happens
                                         // when load group is crossing
                                         // namespace boundary twice and second
                                         // local group depends on the same libraries.
#define FLAG_TLS_NODELETE     0x00000200 // This flag set when there is at least one
                                         // outstanding thread_local dtor
                                         // registered with this soinfo. In such
                                         // a case the actual unload is
                                         // postponed until the last thread_local
                                         // destructor associated with this
                                         // soinfo is executed and this flag is
                                         // unset.
#define FLAG_NEW_SOINFO       0x40000000 // new soinfo format

#define SOINFO_VERSION 4

typedef void (*linker_dtor_function_t)();
typedef void (*linker_ctor_function_t)(int, char**, char**);

class SymbolName {
 public:
  explicit SymbolName(const char* name)
      : name_(name), has_elf_hash_(false), has_gnu_hash_(false),
        elf_hash_(0), gnu_hash_(0) { }

  const char* get_name() {
    return name_;
  }

  uint32_t elf_hash();
  uint32_t gnu_hash();

 private:
  const char* name_;
  bool has_elf_hash_;
  bool has_gnu_hash_;
  uint32_t elf_hash_;
  uint32_t gnu_hash_;

  DISALLOW_IMPLICIT_CONSTRUCTORS(SymbolName);
};

struct version_info {
  constexpr version_info() : elf_hash(0), name(nullptr), target_si(nullptr) {}

  uint32_t elf_hash;
  const char* name;
  const soinfo* target_si;
};

// TODO(dimitry): remove reference from soinfo member functions to this class.
class VersionTracker;

#if defined(__work_around_b_24465209__)
#define SOINFO_NAME_LEN 128
#endif

struct soinfo {
#if defined(__work_around_b_24465209__)
 private:
  char old_name_[SOINFO_NAME_LEN];
#endif
 public:
  const ElfW(Phdr)* phdr;
  size_t phnum;
#if defined(__work_around_b_24465209__)
  ElfW(Addr) unused0; // DO NOT USE, maintained for compatibility.
#endif
  ElfW(Addr) base;
  size_t size;

#if defined(__work_around_b_24465209__)
  uint32_t unused1;  // DO NOT USE, maintained for compatibility.
#endif

  ElfW(Dyn)* dynamic;

#if defined(__work_around_b_24465209__)
  uint32_t unused2; // DO NOT USE, maintained for compatibility
  uint32_t unused3; // DO NOT USE, maintained for compatibility
#endif

  soinfo* next;
 private:
  uint32_t flags_;

  const char* strtab_;
  ElfW(Sym)* symtab_;

  size_t nbucket_;
  size_t nchain_;
  uint32_t* bucket_;
  uint32_t* chain_;

#if defined(__mips__) || !defined(__LP64__)
  // This is only used by mips and mips64, but needs to be here for
  // all 32-bit architectures to preserve binary compatibility.
  ElfW(Addr)** plt_got_;
#endif

#if defined(USE_RELA)
  ElfW(Rela)* plt_rela_;
  size_t plt_rela_count_;

  ElfW(Rela)* rela_;
  size_t rela_count_;
#else
  ElfW(Rel)* plt_rel_;
  size_t plt_rel_count_;

  ElfW(Rel)* rel_;
  size_t rel_count_;
#endif

  linker_ctor_function_t* preinit_array_;
  size_t preinit_array_count_;

  linker_ctor_function_t* init_array_;
  size_t init_array_count_;
  linker_dtor_function_t* fini_array_;
  size_t fini_array_count_;

  linker_ctor_function_t init_func_;
  linker_dtor_function_t fini_func_;

#if defined(__arm__)
 public:
  // ARM EABI section used for stack unwinding.
  uint32_t* ARM_exidx;
  size_t ARM_exidx_count;
 private:
#elif defined(__mips__)
  uint32_t mips_symtabno_;
  uint32_t mips_local_gotno_;
  uint32_t mips_gotsym_;
  bool mips_relocate_got(const VersionTracker& version_tracker,
                         const soinfo_list_t& global_group,
                         const soinfo_list_t& local_group);
#if !defined(__LP64__)
  bool mips_check_and_adjust_fp_modes();
#endif
#endif
  size_t ref_count_;
 public:
  link_map link_map_head;

  bool constructors_called;

  // When you read a virtual address from the ELF file, add this
  // value to get the corresponding address in the process' address space.
  ElfW(Addr) load_bias;

#if !defined(__LP64__)
  bool has_text_relocations;
#endif
  bool has_DT_SYMBOLIC;

 public:
  soinfo(android_namespace_t* ns, const char* name, const struct stat* file_stat,
         off64_t file_offset, int rtld_flags);
  ~soinfo();

  void call_constructors();
  void call_destructors();
  void call_pre_init_constructors();
  bool prelink_image();
  bool link_image(const soinfo_list_t& global_group, const soinfo_list_t& local_group,
                  const android_dlextinfo* extinfo);
  bool protect_relro();

  void add_child(soinfo* child);
  void remove_all_links();

  ino_t get_st_ino() const;
  dev_t get_st_dev() const;
  off64_t get_file_offset() const;

  uint32_t get_rtld_flags() const;
  uint32_t get_dt_flags_1() const;
  void set_dt_flags_1(uint32_t dt_flags_1);

  soinfo_list_t& get_children();
  const soinfo_list_t& get_children() const;

  soinfo_list_t& get_parents();

  bool find_symbol_by_name(SymbolName& symbol_name,
                           const version_info* vi,
                           const ElfW(Sym)** symbol) const;

  ElfW(Sym)* find_symbol_by_address(const void* addr);
  ElfW(Addr) resolve_symbol_address(const ElfW(Sym)* s) const;

  const char* get_string(ElfW(Word) index) const;
  bool can_unload() const;
  bool is_gnu_hash() const;

  bool inline has_min_version(uint32_t min_version __unused) const {
#if defined(__work_around_b_24465209__)
    return (flags_ & FLAG_NEW_SOINFO) != 0 && version_ >= min_version;
#else
    return true;
#endif
  }

  bool is_linked() const;
  bool is_linker() const;
  bool is_main_executable() const;

  void set_linked();
  void set_linker_flag();
  void set_main_executable();
  void set_nodelete();
  void set_tls_nodelete();
  void unset_tls_nodelete();

  size_t increment_ref_count();
  size_t decrement_ref_count();
  size_t get_ref_count() const;

  soinfo* get_local_group_root() const;

  void set_soname(const char* soname);
  const char* get_soname() const;
  const char* get_realpath() const;
  const ElfW(Versym)* get_versym(size_t n) const;
  ElfW(Addr) get_verneed_ptr() const;
  size_t get_verneed_cnt() const;
  ElfW(Addr) get_verdef_ptr() const;
  size_t get_verdef_cnt() const;

  uint32_t get_target_sdk_version() const;

  void set_dt_runpath(const char *);
  const std::vector<std::string>& get_dt_runpath() const;
  android_namespace_t* get_primary_namespace();
  void add_secondary_namespace(android_namespace_t* secondary_ns);
  android_namespace_list_t& get_secondary_namespaces();

  void set_mapped_by_caller(bool reserved_map);
  bool is_mapped_by_caller() const;

  uintptr_t get_handle() const;
  void generate_handle();
  void* to_handle();

 private:
  bool is_image_linked() const;
  void set_image_linked();

  bool elf_lookup(SymbolName& symbol_name, const version_info* vi, uint32_t* symbol_index) const;
  ElfW(Sym)* elf_addr_lookup(const void* addr);
  bool gnu_lookup(SymbolName& symbol_name, const version_info* vi, uint32_t* symbol_index) const;
  ElfW(Sym)* gnu_addr_lookup(const void* addr);

  bool lookup_version_info(const VersionTracker& version_tracker, ElfW(Word) sym,
                           const char* sym_name, const version_info** vi);

  template<typename ElfRelIteratorT>
  bool relocate(const VersionTracker& version_tracker, ElfRelIteratorT&& rel_iterator,
                const soinfo_list_t& global_group, const soinfo_list_t& local_group);
  bool relocate_relr();
  void apply_relr_reloc(ElfW(Addr) offset);

 private:
  // This part of the structure is only available
  // when FLAG_NEW_SOINFO is set in this->flags.
  uint32_t version_;

  // version >= 0
  dev_t st_dev_;
  ino_t st_ino_;

  // dependency graph
  soinfo_list_t children_;
  soinfo_list_t parents_;

  // version >= 1
  off64_t file_offset_;
  uint32_t rtld_flags_;
  uint32_t dt_flags_1_;
  size_t strtab_size_;

  // version >= 2

  size_t gnu_nbucket_;
  uint32_t* gnu_bucket_;
  uint32_t* gnu_chain_;
  uint32_t gnu_maskwords_;
  uint32_t gnu_shift2_;
  ElfW(Addr)* gnu_bloom_filter_;

  soinfo* local_group_root_;

  uint8_t* android_relocs_;
  size_t android_relocs_size_;

  const char* soname_;
  std::string realpath_;

  const ElfW(Versym)* versym_;

  ElfW(Addr) verdef_ptr_;
  size_t verdef_cnt_;

  ElfW(Addr) verneed_ptr_;
  size_t verneed_cnt_;

  uint32_t target_sdk_version_;

  // version >= 3
  std::vector<std::string> dt_runpath_;
  android_namespace_t* primary_namespace_;
  android_namespace_list_t secondary_namespaces_;
  uintptr_t handle_;

  friend soinfo* get_libdl_info(const char* linker_path,
                                const soinfo& linker_si,
                                const link_map& linker_map);

  // version >= 4
  ElfW(Relr)* relr_;
  size_t relr_count_;
};

// This function is used by dlvsym() to calculate hash of sym_ver
uint32_t calculate_elf_hash(const char* name);

const char* fix_dt_needed(const char* dt_needed, const char* sopath);

template<typename F>
void for_each_dt_needed(const soinfo* si, F action) {
  for (const ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
    if (d->d_tag == DT_NEEDED) {
      action(fix_dt_needed(si->get_string(d->d_un.d_val), si->get_realpath()));
    }
  }
}