linker/dlfcn.cpp - android_bionic - Gitiles

 /*
  * Copyright (C) 2007 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.
  */

 #include "linker.h"
 #include "linker_cfi.h"
 #include "linker_globals.h"
 #include "linker_dlwarning.h"

 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <android/api-level.h>

 #include <bionic/pthread_internal.h>
 #include "private/bionic_tls.h"
 #include "private/ScopedPthreadMutexLocker.h"
 #include "private/ThreadLocalBuffer.h"

 static pthread_mutex_t g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

 static char* __bionic_set_dlerror(char* new_value) {
   char** dlerror_slot = &reinterpret_cast<char**>(__get_tls())[TLS_SLOT_DLERROR];

   char* old_value = *dlerror_slot;
   *dlerror_slot = new_value;
   return old_value;
 }

 static void __bionic_format_dlerror(const char* msg, const char* detail) {
   char* buffer = __get_thread()->dlerror_buffer;
   strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE);
   if (detail != nullptr) {
     strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
     strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
   }

   __bionic_set_dlerror(buffer);
 }

 char* __dlerror() {
   char* old_value = __bionic_set_dlerror(nullptr);
   return old_value;
 }

 void __android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
 }

 void __android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   do_android_update_LD_LIBRARY_PATH(ld_library_path);
 }

 static void* dlopen_ext(const char* filename,
                         int flags,
                         const android_dlextinfo* extinfo,
                         const void* caller_addr) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   g_linker_logger.ResetState();
   void* result = do_dlopen(filename, flags, extinfo, caller_addr);
   if (result == nullptr) {
     __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
     return nullptr;
   }
   return result;
 }

 void* __android_dlopen_ext(const char* filename,
                            int flags,
                            const android_dlextinfo* extinfo,
                            const void* caller_addr) {
   return dlopen_ext(filename, flags, extinfo, caller_addr);
 }

 void* __dlopen(const char* filename, int flags, const void* caller_addr) {
   return dlopen_ext(filename, flags, nullptr, caller_addr);
 }

 void* dlsym_impl(void* handle, const char* symbol, const char* version, const void* caller_addr) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   g_linker_logger.ResetState();
   void* result;
   if (!do_dlsym(handle, symbol, version, caller_addr, &result)) {
     __bionic_format_dlerror(linker_get_error_buffer(), nullptr);
     return nullptr;
   }

   return result;
 }

 void* __dlsym(void* handle, const char* symbol, const void* caller_addr) {
   return dlsym_impl(handle, symbol, nullptr, caller_addr);
 }

 void* __dlvsym(void* handle, const char* symbol, const char* version, const void* caller_addr) {
   return dlsym_impl(handle, symbol, version, caller_addr);
 }

 int __dladdr(const void* addr, Dl_info* info) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   return do_dladdr(addr, info);
 }

 int __dlclose(void* handle) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   int result = do_dlclose(handle);
   if (result != 0) {
     __bionic_format_dlerror("dlclose failed", linker_get_error_buffer());
   }
   return result;
 }

 // This function is needed by libgcc.a (this is why there is no prefix for this one)
 int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   return do_dl_iterate_phdr(cb, data);
 }

 #if defined(__arm__)
 _Unwind_Ptr __dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   return do_dl_unwind_find_exidx(pc, pcount);
 }
 #endif

 void __android_set_application_target_sdk_version(uint32_t target) {
   // lock to avoid modification in the middle of dlopen.
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   set_application_target_sdk_version(target);
 }

 uint32_t __android_get_application_target_sdk_version() {
   return get_application_target_sdk_version();
 }

 void __android_dlwarning(void* obj, void (*f)(void*, const char*)) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   get_dlwarning(obj, f);
 }

 bool __android_init_anonymous_namespace(const char* shared_libs_sonames,
                                          const char* library_search_path) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);
   bool success = init_anonymous_namespace(shared_libs_sonames, library_search_path);
   if (!success) {
     __bionic_format_dlerror("android_init_anonymous_namespace failed", linker_get_error_buffer());
   }

   return success;
 }

 android_namespace_t* __android_create_namespace(const char* name,
                                                 const char* ld_library_path,
                                                 const char* default_library_path,
                                                 uint64_t type,
                                                 const char* permitted_when_isolated_path,
                                                 android_namespace_t* parent_namespace,
                                                 const void* caller_addr) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);

   android_namespace_t* result = create_namespace(caller_addr,
                                                  name,
                                                  ld_library_path,
                                                  default_library_path,
                                                  type,
                                                  permitted_when_isolated_path,
                                                  parent_namespace);

   if (result == nullptr) {
     __bionic_format_dlerror("android_create_namespace failed", linker_get_error_buffer());
   }

   return result;
 }

 bool __android_link_namespaces(android_namespace_t* namespace_from,
                                android_namespace_t* namespace_to,
                                const char* shared_libs_sonames) {
   ScopedPthreadMutexLocker locker(&g_dl_mutex);

   bool success = link_namespaces(namespace_from, namespace_to, shared_libs_sonames);

   if (!success) {
     __bionic_format_dlerror("android_link_namespaces failed", linker_get_error_buffer());
   }

   return success;
 }

 void __cfi_fail(uint64_t CallSiteTypeId, void* Ptr, void *DiagData, void *CallerPc) {
   CFIShadowWriter::CfiFail(CallSiteTypeId, Ptr, DiagData, CallerPc);
 }

 // name_offset: starting index of the name in libdl_info.strtab
 #define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
     { name_offset, \
       reinterpret_cast<Elf32_Addr>(value), \
       /* st_size */ 0, \
       ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
       /* st_other */ 0, \
       shndx, \
     }

 #define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
     { name_offset, \
       ((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
       /* st_other */ 0, \
       shndx, \
       reinterpret_cast<Elf64_Addr>(value), \
       /* st_size */ 0, \
     }

 static const char ANDROID_LIBDL_STRTAB[] =
   // 0000000000111111 11112222222222333 333333344444444 44555555555566666 6666677777777778 8888888889999999999
   // 0123456789012345 67890123456789012 345678901234567 89012345678901234 5678901234567890 1234567890123456789
     "__loader_dlopen\0__loader_dlclose\0__loader_dlsym\0__loader_dlerror\0__loader_dladdr\0__loader_android_up"
   // 1*
   // 000000000011111111112 2222222223333333333444444444455555555 5566666666667777777777888 88888889999999999
   // 012345678901234567890 1234567890123456789012345678901234567 8901234567890123456789012 34567890123456789
     "date_LD_LIBRARY_PATH\0__loader_android_get_LD_LIBRARY_PATH\0__loader_dl_iterate_phdr\0__loader_android_"
   // 2*
   // 00000000001 1111111112222222222333333333344444444445555555555666 6666666777777777788888888889999999999
   // 01234567890 1234567890123456789012345678901234567890123456789012 3456789012345678901234567890123456789
     "dlopen_ext\0__loader_android_set_application_target_sdk_version\0__loader_android_get_application_targ"
   // 3*
   // 000000000011111 111112222222222333333333344444444445555555 5556666666666777777777788888888889 999999999
   // 012345678901234 567890123456789012345678901234567890123456 7890123456789012345678901234567890 123456789
     "et_sdk_version\0__loader_android_init_anonymous_namespace\0__loader_android_create_namespace\0__loader_"
   // 4*
   // 0000000 000111111111122222222223333 333333444444444455 555555556666666666777777777788888 888889999999999
   // 0123456 789012345678901234567890123 456789012345678901 234567890123456789012345678901234 567890123456789
     "dlvsym\0__loader_android_dlwarning\0__loader_cfi_fail\0__loader_android_link_namespaces\0"
 #if defined(__arm__)
   // 485
     "__loader_dl_unwind_find_exidx\0"
 #endif
     ;

 static ElfW(Sym) g_libdl_symtab[] = {
   // Total length of libdl_info.strtab, including trailing 0.
   // This is actually the STH_UNDEF entry. Technically, it's
   // supposed to have st_name == 0, but instead, it points to an index
   // in the strtab with a \0 to make iterating through the symtab easier.
   ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0),
   ELFW(SYM_INITIALIZER)(  0, &__dlopen, 1),
   ELFW(SYM_INITIALIZER)( 16, &__dlclose, 1),
   ELFW(SYM_INITIALIZER)( 33, &__dlsym, 1),
   ELFW(SYM_INITIALIZER)( 48, &__dlerror, 1),
   ELFW(SYM_INITIALIZER)( 65, &__dladdr, 1),
   ELFW(SYM_INITIALIZER)( 81, &__android_update_LD_LIBRARY_PATH, 1),
   ELFW(SYM_INITIALIZER)(121, &__android_get_LD_LIBRARY_PATH, 1),
   ELFW(SYM_INITIALIZER)(158, &dl_iterate_phdr, 1),
   ELFW(SYM_INITIALIZER)(183, &__android_dlopen_ext, 1),
   ELFW(SYM_INITIALIZER)(211, &__android_set_application_target_sdk_version, 1),
   ELFW(SYM_INITIALIZER)(263, &__android_get_application_target_sdk_version, 1),
   ELFW(SYM_INITIALIZER)(315, &__android_init_anonymous_namespace, 1),
   ELFW(SYM_INITIALIZER)(357, &__android_create_namespace, 1),
   ELFW(SYM_INITIALIZER)(391, &__dlvsym, 1),
   ELFW(SYM_INITIALIZER)(407, &__android_dlwarning, 1),
   ELFW(SYM_INITIALIZER)(434, &__cfi_fail, 1),
   ELFW(SYM_INITIALIZER)(452, &__android_link_namespaces, 1),
 #if defined(__arm__)
   ELFW(SYM_INITIALIZER)(485, &__dl_unwind_find_exidx, 1),
 #endif
 };

 // Fake out a hash table with a single bucket.
 //
 // A search of the hash table will look through g_libdl_symtab starting with index 1, then
 // use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
 // walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
 //
 // That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
 // of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not
 // a real symbol). (See soinfo_elf_lookup().)
 //
 // Note that adding any new symbols here requires stubbing them out in libdl.
 static unsigned g_libdl_buckets[1] = { 1 };
 #if defined(__arm__)
 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 0 };
 #else
 static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 0 };
 #endif

 static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));
 static soinfo* __libdl_info = nullptr;

 // This is used by the dynamic linker. Every process gets these symbols for free.
 soinfo* get_libdl_info(const char* linker_path) {
   if (__libdl_info == nullptr) {
     __libdl_info = new (__libdl_info_buf) soinfo(&g_default_namespace, linker_path, nullptr, 0, 0);
     __libdl_info->flags_ |= FLAG_LINKED;
     __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->ref_count_ = 1;
     __libdl_info->strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB);
     __libdl_info->local_group_root_ = __libdl_info;
     __libdl_info->soname_ = "ld-android.so";
     __libdl_info->target_sdk_version_ = __ANDROID_API__;
     __libdl_info->generate_handle();
 #if defined(__work_around_b_24465209__)
     strlcpy(__libdl_info->old_name_, __libdl_info->soname_, sizeof(__libdl_info->old_name_));
 #endif
   }

   return __libdl_info;
 }
	/*
	* Copyright (C) 2007 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.
	*/

	#include "linker.h"
	#include "linker_cfi.h"
	#include "linker_globals.h"
	#include "linker_dlwarning.h"

	#include <pthread.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <android/api-level.h>

	#include <bionic/pthread_internal.h>
	#include "private/bionic_tls.h"
	#include "private/ScopedPthreadMutexLocker.h"
	#include "private/ThreadLocalBuffer.h"

	static pthread_mutex_t g_dl_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

	static char* __bionic_set_dlerror(char* new_value) {
	char dlerror_slot = &reinterpret_cast<char>(__get_tls())[TLS_SLOT_DLERROR];

	char* old_value = *dlerror_slot;
	*dlerror_slot = new_value;
	return old_value;
	}

	static void __bionic_format_dlerror(const char* msg, const char* detail) {
	char* buffer = __get_thread()->dlerror_buffer;
	strlcpy(buffer, msg, __BIONIC_DLERROR_BUFFER_SIZE);
	if (detail != nullptr) {
	strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
	strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
	}

	__bionic_set_dlerror(buffer);
	}

	char* __dlerror() {
	char* old_value = __bionic_set_dlerror(nullptr);
	return old_value;
	}

	void __android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	do_android_get_LD_LIBRARY_PATH(buffer, buffer_size);
	}

	void __android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	do_android_update_LD_LIBRARY_PATH(ld_library_path);
	}

	static void* dlopen_ext(const char* filename,
	int flags,
	const android_dlextinfo* extinfo,
	const void* caller_addr) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	g_linker_logger.ResetState();
	void* result = do_dlopen(filename, flags, extinfo, caller_addr);
	if (result == nullptr) {
	__bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
	return nullptr;
	}
	return result;
	}

	void* __android_dlopen_ext(const char* filename,
	int flags,
	const android_dlextinfo* extinfo,
	const void* caller_addr) {
	return dlopen_ext(filename, flags, extinfo, caller_addr);
	}

	void* __dlopen(const char* filename, int flags, const void* caller_addr) {
	return dlopen_ext(filename, flags, nullptr, caller_addr);
	}

	void* dlsym_impl(void* handle, const char* symbol, const char* version, const void* caller_addr) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	g_linker_logger.ResetState();
	void* result;
	if (!do_dlsym(handle, symbol, version, caller_addr, &result)) {
	__bionic_format_dlerror(linker_get_error_buffer(), nullptr);
	return nullptr;
	}

	return result;
	}

	void* __dlsym(void* handle, const char* symbol, const void* caller_addr) {
	return dlsym_impl(handle, symbol, nullptr, caller_addr);
	}

	void* __dlvsym(void* handle, const char* symbol, const char* version, const void* caller_addr) {
	return dlsym_impl(handle, symbol, version, caller_addr);
	}

	int __dladdr(const void* addr, Dl_info* info) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	return do_dladdr(addr, info);
	}

	int __dlclose(void* handle) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	int result = do_dlclose(handle);
	if (result != 0) {
	__bionic_format_dlerror("dlclose failed", linker_get_error_buffer());
	}
	return result;
	}

	// This function is needed by libgcc.a (this is why there is no prefix for this one)
	int dl_iterate_phdr(int (cb)(dl_phdr_info info, size_t size, void* data), void* data) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	return do_dl_iterate_phdr(cb, data);
	}

	#if defined(__arm__)
	_Unwind_Ptr __dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	return do_dl_unwind_find_exidx(pc, pcount);
	}
	#endif

	void __android_set_application_target_sdk_version(uint32_t target) {
	// lock to avoid modification in the middle of dlopen.
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	set_application_target_sdk_version(target);
	}

	uint32_t __android_get_application_target_sdk_version() {
	return get_application_target_sdk_version();
	}

	void __android_dlwarning(void* obj, void (f)(void, const char*)) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	get_dlwarning(obj, f);
	}

	bool __android_init_anonymous_namespace(const char* shared_libs_sonames,
	const char* library_search_path) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);
	bool success = init_anonymous_namespace(shared_libs_sonames, library_search_path);
	if (!success) {
	__bionic_format_dlerror("android_init_anonymous_namespace failed", linker_get_error_buffer());
	}

	return success;
	}

	android_namespace_t* __android_create_namespace(const char* name,
	const char* ld_library_path,
	const char* default_library_path,
	uint64_t type,
	const char* permitted_when_isolated_path,
	android_namespace_t* parent_namespace,
	const void* caller_addr) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);

	android_namespace_t* result = create_namespace(caller_addr,
	name,
	ld_library_path,
	default_library_path,
	type,
	permitted_when_isolated_path,
	parent_namespace);

	if (result == nullptr) {
	__bionic_format_dlerror("android_create_namespace failed", linker_get_error_buffer());
	}

	return result;
	}

	bool __android_link_namespaces(android_namespace_t* namespace_from,
	android_namespace_t* namespace_to,
	const char* shared_libs_sonames) {
	ScopedPthreadMutexLocker locker(&g_dl_mutex);

	bool success = link_namespaces(namespace_from, namespace_to, shared_libs_sonames);

	if (!success) {
	__bionic_format_dlerror("android_link_namespaces failed", linker_get_error_buffer());
	}

	return success;
	}

	void __cfi_fail(uint64_t CallSiteTypeId, void* Ptr, void DiagData, void CallerPc) {
	CFIShadowWriter::CfiFail(CallSiteTypeId, Ptr, DiagData, CallerPc);
	}

	// name_offset: starting index of the name in libdl_info.strtab
	#define ELF32_SYM_INITIALIZER(name_offset, value, shndx) \
	{ name_offset, \
	reinterpret_cast<Elf32_Addr>(value), \
	/* st_size */ 0, \
	((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
	/* st_other */ 0, \
	shndx, \
	}

	#define ELF64_SYM_INITIALIZER(name_offset, value, shndx) \
	{ name_offset, \
	((shndx) == 0) ? 0 : (STB_GLOBAL << 4), \
	/* st_other */ 0, \
	shndx, \
	reinterpret_cast<Elf64_Addr>(value), \
	/* st_size */ 0, \
	}

	static const char ANDROID_LIBDL_STRTAB[] =
	// 0000000000111111 11112222222222333 333333344444444 44555555555566666 6666677777777778 8888888889999999999
	// 0123456789012345 67890123456789012 345678901234567 89012345678901234 5678901234567890 1234567890123456789
	"__loader_dlopen\0__loader_dlclose\0__loader_dlsym\0__loader_dlerror\0__loader_dladdr\0__loader_android_up"
	// 1*
	// 000000000011111111112 2222222223333333333444444444455555555 5566666666667777777777888 88888889999999999
	// 012345678901234567890 1234567890123456789012345678901234567 8901234567890123456789012 34567890123456789
	"date_LD_LIBRARY_PATH\0__loader_android_get_LD_LIBRARY_PATH\0__loader_dl_iterate_phdr\0__loader_android_"
	// 2*
	// 00000000001 1111111112222222222333333333344444444445555555555666 6666666777777777788888888889999999999
	// 01234567890 1234567890123456789012345678901234567890123456789012 3456789012345678901234567890123456789
	"dlopen_ext\0__loader_android_set_application_target_sdk_version\0__loader_android_get_application_targ"
	// 3*
	// 000000000011111 111112222222222333333333344444444445555555 5556666666666777777777788888888889 999999999
	// 012345678901234 567890123456789012345678901234567890123456 7890123456789012345678901234567890 123456789
	"et_sdk_version\0__loader_android_init_anonymous_namespace\0__loader_android_create_namespace\0__loader_"
	// 4*
	// 0000000 000111111111122222222223333 333333444444444455 555555556666666666777777777788888 888889999999999
	// 0123456 789012345678901234567890123 456789012345678901 234567890123456789012345678901234 567890123456789
	"dlvsym\0__loader_android_dlwarning\0__loader_cfi_fail\0__loader_android_link_namespaces\0"
	#if defined(__arm__)
	// 485
	"__loader_dl_unwind_find_exidx\0"
	#endif
	;

	static ElfW(Sym) g_libdl_symtab[] = {
	// Total length of libdl_info.strtab, including trailing 0.
	// This is actually the STH_UNDEF entry. Technically, it's
	// supposed to have st_name == 0, but instead, it points to an index
	// in the strtab with a \0 to make iterating through the symtab easier.
	ELFW(SYM_INITIALIZER)(sizeof(ANDROID_LIBDL_STRTAB) - 1, nullptr, 0),
	ELFW(SYM_INITIALIZER)( 0, &__dlopen, 1),
	ELFW(SYM_INITIALIZER)( 16, &__dlclose, 1),
	ELFW(SYM_INITIALIZER)( 33, &__dlsym, 1),
	ELFW(SYM_INITIALIZER)( 48, &__dlerror, 1),
	ELFW(SYM_INITIALIZER)( 65, &__dladdr, 1),
	ELFW(SYM_INITIALIZER)( 81, &__android_update_LD_LIBRARY_PATH, 1),
	ELFW(SYM_INITIALIZER)(121, &__android_get_LD_LIBRARY_PATH, 1),
	ELFW(SYM_INITIALIZER)(158, &dl_iterate_phdr, 1),
	ELFW(SYM_INITIALIZER)(183, &__android_dlopen_ext, 1),
	ELFW(SYM_INITIALIZER)(211, &__android_set_application_target_sdk_version, 1),
	ELFW(SYM_INITIALIZER)(263, &__android_get_application_target_sdk_version, 1),
	ELFW(SYM_INITIALIZER)(315, &__android_init_anonymous_namespace, 1),
	ELFW(SYM_INITIALIZER)(357, &__android_create_namespace, 1),
	ELFW(SYM_INITIALIZER)(391, &__dlvsym, 1),
	ELFW(SYM_INITIALIZER)(407, &__android_dlwarning, 1),
	ELFW(SYM_INITIALIZER)(434, &__cfi_fail, 1),
	ELFW(SYM_INITIALIZER)(452, &__android_link_namespaces, 1),
	#if defined(__arm__)
	ELFW(SYM_INITIALIZER)(485, &__dl_unwind_find_exidx, 1),
	#endif
	};

	// Fake out a hash table with a single bucket.
	//
	// A search of the hash table will look through g_libdl_symtab starting with index 1, then
	// use g_libdl_chains to find the next index to look at. g_libdl_chains should be set up to
	// walk through every element in g_libdl_symtab, and then end with 0 (sentinel value).
	//
	// That is, g_libdl_chains should look like { 0, 2, 3, ... N, 0 } where N is the number
	// of actual symbols, or nelems(g_libdl_symtab)-1 (since the first element of g_libdl_symtab is not
	// a real symbol). (See soinfo_elf_lookup().)
	//
	// Note that adding any new symbols here requires stubbing them out in libdl.
	static unsigned g_libdl_buckets[1] = { 1 };
	#if defined(__arm__)
	static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 0 };
	#else
	static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 0 };
	#endif

	static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));
	static soinfo* __libdl_info = nullptr;

	// This is used by the dynamic linker. Every process gets these symbols for free.
	soinfo* get_libdl_info(const char* linker_path) {
	if (__libdl_info == nullptr) {
	__libdl_info = new (__libdl_info_buf) soinfo(&g_default_namespace, linker_path, nullptr, 0, 0);
	__libdl_info->flags_ \|= FLAG_LINKED;
	__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->ref_count_ = 1;
	__libdl_info->strtab_size_ = sizeof(ANDROID_LIBDL_STRTAB);
	__libdl_info->local_group_root_ = __libdl_info;
	__libdl_info->soname_ = "ld-android.so";
	__libdl_info->target_sdk_version_ = __ANDROID_API__;
	__libdl_info->generate_handle();
	#if defined(__work_around_b_24465209__)
	strlcpy(__libdl_info->old_name_, __libdl_info->soname_, sizeof(__libdl_info->old_name_));
	#endif
	}

	return __libdl_info;
	}