linker/linker.h - platform/bionic - Git at Google

 /*
  * Copyright (C) 2008 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.
  */

 #ifndef _LINKER_H_
 #define _LINKER_H_

 #include <elf.h>
 #include <inttypes.h>
 #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 { \
       __libc_format_buffer(linker_get_error_buffer(), linker_get_error_buffer_size(), fmt, ##x); \
       /* If LD_DEBUG is set high enough, log every dlerror(3) message. */ \
       DEBUG("%s\n", linker_get_error_buffer()); \
     } while (false)

 #define DL_WARN(fmt, x...) \
     do { \
       __libc_format_log(ANDROID_LOG_WARN, "linker", fmt, ##x); \
       __libc_format_fd(2, "WARNING: linker: "); \
       __libc_format_fd(2, fmt, ##x); \
       __libc_format_fd(2, "\n"); \
     } while (false)

 #if defined(__LP64__)
 #define ELFW(what) ELF64_ ## what
 #else
 #define ELFW(what) ELF32_ ## what
 #endif

 // mips64 interprets Elf64_Rel structures' r_info field differently.
 // bionic (like other C libraries) has macros that assume regular ELF files,
 // but the dynamic linker needs to be able to load mips64 ELF files.
 #if defined(__mips__) && defined(__LP64__)
 #undef ELF64_R_SYM
 #undef ELF64_R_TYPE
 #undef ELF64_R_INFO
 #define ELF64_R_SYM(info)   (((info) >> 0) & 0xffffffff)
 #define ELF64_R_SSYM(info)  (((info) >> 32) & 0xff)
 #define ELF64_R_TYPE3(info) (((info) >> 40) & 0xff)
 #define ELF64_R_TYPE2(info) (((info) >> 48) & 0xff)
 #define ELF64_R_TYPE(info)  (((info) >> 56) & 0xff)
 #endif

 // Returns the address of the page containing address 'x'.
 #define PAGE_START(x)  ((x) & PAGE_MASK)

 // Returns the offset of address 'x' in its page.
 #define PAGE_OFFSET(x) ((x) & ~PAGE_MASK)

 // Returns the address of the next page after address 'x', unless 'x' is
 // itself at the start of a page.
 #define PAGE_END(x)    PAGE_START((x) + (PAGE_SIZE-1))

 #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_VERSION 1

 #define SOINFO_NAME_LEN 128

 typedef void (*linker_function_t)();

 // Android uses RELA for aarch64 and x86_64. mips64 still uses REL.
 #if defined(__aarch64__) || defined(__x86_64__)
 #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;
   size_t phnum;
   ElfW(Addr) entry;
   ElfW(Addr) base;
   size_t size;

 #ifndef __LP64__
   uint32_t unused1;  // DO NOT USE, maintained for compatibility.
 #endif

   ElfW(Dyn)* dynamic;

 #ifndef __LP64__
   uint32_t unused2; // DO NOT USE, maintained for compatibility
   uint32_t unused3; // DO NOT USE, maintained for compatibility
 #endif

   soinfo* next;
   unsigned flags;

   const char* strtab;
   ElfW(Sym)* symtab;

   size_t nbucket;
   size_t nchain;
   unsigned* bucket;
   unsigned* 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_function_t* preinit_array;
   size_t preinit_array_count;

   linker_function_t* init_array;
   size_t init_array_count;
   linker_function_t* fini_array;
   size_t fini_array_count;

   linker_function_t init_func;
   linker_function_t fini_func;

 #if defined(__arm__)
   // ARM EABI section used for stack unwinding.
   unsigned* ARM_exidx;
   size_t ARM_exidx_count;
 #elif defined(__mips__)
   unsigned mips_symtabno;
   unsigned mips_local_gotno;
   unsigned mips_gotsym;
 #endif

   size_t ref_count;
   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;

   soinfo(const char* name, const struct stat* file_stat);

   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);
   void set_has_ifuncs(bool ifunc);
   ino_t get_st_ino();
   dev_t get_st_dev();
   bool get_has_ifuncs();

   soinfo_list_t& get_children();

   bool inline has_min_version(uint32_t min_version) {
     return (flags & FLAG_NEW_SOINFO) != 0 && version >= min_version;
   }
  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);
   void resolve_ifunc_symbols();

  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
   bool has_ifuncs;
 };

 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);
 soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo);
 void do_dlclose(soinfo* si);

 ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start);
 soinfo* find_containing_library(const void* addr);

 ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr);
 ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);

 void debuggerd_init();
 extern "C" abort_msg_t* g_abort_message;
 extern "C" void notify_gdb_of_libraries();

 char* linker_get_error_buffer();
 size_t linker_get_error_buffer_size();

 #endif
	/*
	* Copyright (C) 2008 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.
	*/

	#ifndef _LINKER_H_
	#define _LINKER_H_

	#include <elf.h>
	#include <inttypes.h>
	#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 { \
	__libc_format_buffer(linker_get_error_buffer(), linker_get_error_buffer_size(), fmt, ##x); \
	/* If LD_DEBUG is set high enough, log every dlerror(3) message. */ \
	DEBUG("%s\n", linker_get_error_buffer()); \
	} while (false)

	#define DL_WARN(fmt, x...) \
	do { \
	__libc_format_log(ANDROID_LOG_WARN, "linker", fmt, ##x); \
	__libc_format_fd(2, "WARNING: linker: "); \
	__libc_format_fd(2, fmt, ##x); \
	__libc_format_fd(2, "\n"); \
	} while (false)

	#if defined(__LP64__)
	#define ELFW(what) ELF64_ ## what
	#else
	#define ELFW(what) ELF32_ ## what
	#endif

	// mips64 interprets Elf64_Rel structures' r_info field differently.
	// bionic (like other C libraries) has macros that assume regular ELF files,
	// but the dynamic linker needs to be able to load mips64 ELF files.
	#if defined(__mips__) && defined(__LP64__)
	#undef ELF64_R_SYM
	#undef ELF64_R_TYPE
	#undef ELF64_R_INFO
	#define ELF64_R_SYM(info) (((info) >> 0) & 0xffffffff)
	#define ELF64_R_SSYM(info) (((info) >> 32) & 0xff)
	#define ELF64_R_TYPE3(info) (((info) >> 40) & 0xff)
	#define ELF64_R_TYPE2(info) (((info) >> 48) & 0xff)
	#define ELF64_R_TYPE(info) (((info) >> 56) & 0xff)
	#endif

	// Returns the address of the page containing address 'x'.
	#define PAGE_START(x) ((x) & PAGE_MASK)

	// Returns the offset of address 'x' in its page.
	#define PAGE_OFFSET(x) ((x) & ~PAGE_MASK)

	// Returns the address of the next page after address 'x', unless 'x' is
	// itself at the start of a page.
	#define PAGE_END(x) PAGE_START((x) + (PAGE_SIZE-1))

	#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_VERSION 1

	#define SOINFO_NAME_LEN 128

	typedef void (*linker_function_t)();

	// Android uses RELA for aarch64 and x86_64. mips64 still uses REL.
	#if defined(__aarch64__) \|\| defined(__x86_64__)
	#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;
	size_t phnum;
	ElfW(Addr) entry;
	ElfW(Addr) base;
	size_t size;

	#ifndef __LP64__
	uint32_t unused1; // DO NOT USE, maintained for compatibility.
	#endif

	ElfW(Dyn)* dynamic;

	#ifndef __LP64__
	uint32_t unused2; // DO NOT USE, maintained for compatibility
	uint32_t unused3; // DO NOT USE, maintained for compatibility
	#endif

	soinfo* next;
	unsigned flags;

	const char* strtab;
	ElfW(Sym)* symtab;

	size_t nbucket;
	size_t nchain;
	unsigned* bucket;
	unsigned* 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_function_t* preinit_array;
	size_t preinit_array_count;

	linker_function_t* init_array;
	size_t init_array_count;
	linker_function_t* fini_array;
	size_t fini_array_count;

	linker_function_t init_func;
	linker_function_t fini_func;

	#if defined(__arm__)
	// ARM EABI section used for stack unwinding.
	unsigned* ARM_exidx;
	size_t ARM_exidx_count;
	#elif defined(__mips__)
	unsigned mips_symtabno;
	unsigned mips_local_gotno;
	unsigned mips_gotsym;
	#endif

	size_t ref_count;
	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;

	soinfo(const char* name, const struct stat* file_stat);

	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);
	void set_has_ifuncs(bool ifunc);
	ino_t get_st_ino();
	dev_t get_st_dev();
	bool get_has_ifuncs();

	soinfo_list_t& get_children();

	bool inline has_min_version(uint32_t min_version) {
	return (flags & FLAG_NEW_SOINFO) != 0 && version >= min_version;
	}
	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);
	void resolve_ifunc_symbols();

	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
	bool has_ifuncs;
	};

	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);
	soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo);
	void do_dlclose(soinfo* si);

	ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start);
	soinfo* find_containing_library(const void* addr);

	ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr);
	ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);

	void debuggerd_init();
	extern "C" abort_msg_t* g_abort_message;
	extern "C" void notify_gdb_of_libraries();

	char* linker_get_error_buffer();
	size_t linker_get_error_buffer_size();

	#endif