linker/dlfcn.cpp - platform_bionic - Gitiles

 /*
  * Copyright (C) 2007 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 "linker.h"

 #include <dlfcn.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <stdlib.h>

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

 /* This file hijacks the symbols stubbed out in libdl.so. */

 static pthread_mutex_t gDlMutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;

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

   const 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 != NULL) {
     strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
     strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
   }

   __bionic_set_dlerror(buffer);
 }

 const char* dlerror() {
   const char* old_value = __bionic_set_dlerror(NULL);
   return old_value;
 }

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

 void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
   ScopedPthreadMutexLocker locker(&gDlMutex);
   do_android_update_LD_LIBRARY_PATH(ld_library_path);
 }

 void* dlopen(const char* filename, int flags) {
   ScopedPthreadMutexLocker locker(&gDlMutex);
   soinfo* result = do_dlopen(filename, flags);
   if (result == NULL) {
     __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
     return NULL;
   }
   return result;
 }

 void* dlsym(void* handle, const char* symbol) {
   ScopedPthreadMutexLocker locker(&gDlMutex);

   if (handle == NULL) {
     __bionic_format_dlerror("dlsym library handle is null", NULL);
     return NULL;
   }
   if (symbol == NULL) {
     __bionic_format_dlerror("dlsym symbol name is null", NULL);
     return NULL;
   }

   soinfo* found = NULL;
   ElfW(Sym)* sym = NULL;
   if (handle == RTLD_DEFAULT) {
     sym = dlsym_linear_lookup(symbol, &found, NULL);
   } else if (handle == RTLD_NEXT) {
     void* ret_addr = __builtin_return_address(0);
     soinfo* si = find_containing_library(ret_addr);

     sym = NULL;
     if (si && si->next) {
       sym = dlsym_linear_lookup(symbol, &found, si->next);
     }
   } else {
     found = reinterpret_cast<soinfo*>(handle);
     sym = dlsym_handle_lookup(found, symbol);
   }

   if (sym != NULL) {
     unsigned bind = ELF_ST_BIND(sym->st_info);

     if (bind == STB_GLOBAL && sym->st_shndx != 0) {
       return reinterpret_cast<void*>(sym->st_value + found->load_bias);
     }

     __bionic_format_dlerror("symbol found but not global", symbol);
     return NULL;
   } else {
     __bionic_format_dlerror("undefined symbol", symbol);
     return NULL;
   }
 }

 int dladdr(const void* addr, Dl_info* info) {
   ScopedPthreadMutexLocker locker(&gDlMutex);

   // Determine if this address can be found in any library currently mapped.
   soinfo* si = find_containing_library(addr);
   if (si == NULL) {
     return 0;
   }

   memset(info, 0, sizeof(Dl_info));

   info->dli_fname = si->name;
   // Address at which the shared object is loaded.
   info->dli_fbase = (void*) si->base;

   // Determine if any symbol in the library contains the specified address.
   ElfW(Sym)* sym = dladdr_find_symbol(si, addr);
   if (sym != NULL) {
     info->dli_sname = si->strtab + sym->st_name;
     info->dli_saddr = (void*)(si->load_bias + sym->st_value);
   }

   return 1;
 }

 int dlclose(void* handle) {
   ScopedPthreadMutexLocker locker(&gDlMutex);
   return do_dlclose(reinterpret_cast<soinfo*>(handle));
 }

 // 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>(reinterpret_cast<void*>(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>(reinterpret_cast<void*>(value)), \
       /* st_size */ 0, \
     }

 #if defined(__arm__)
   // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
   // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
 #  define ANDROID_LIBDL_STRTAB \
     "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0dl_unwind_find_exidx\0"
 #elif defined(__aarch64__) || defined(__i386__) || defined(__mips__) || defined(__x86_64__)
   // 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
   // 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
 #  define ANDROID_LIBDL_STRTAB \
     "dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0"
 #else
 #  error Unsupported architecture. Only arm, arm64, mips, mips64, x86 and x86_64 are presently supported.
 #endif

 static ElfW(Sym) gLibDlSymtab[] = {
   // 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, NULL, 0),
   ELFW(SYM_INITIALIZER)(  0, &dlopen, 1),
   ELFW(SYM_INITIALIZER)(  7, &dlclose, 1),
   ELFW(SYM_INITIALIZER)( 15, &dlsym, 1),
   ELFW(SYM_INITIALIZER)( 21, &dlerror, 1),
   ELFW(SYM_INITIALIZER)( 29, &dladdr, 1),
   ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1),
   ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1),
   ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1),
 #if defined(__arm__)
   ELFW(SYM_INITIALIZER)(111, &dl_unwind_find_exidx, 1),
 #endif
 };

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

 // This is used by the dynamic linker. Every process gets these symbols for free.
 soinfo libdl_info = {
     "libdl.so",

     .phdr = 0,
     .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 = gLibDlSymtab,

     .nbucket = sizeof(gLibDlBuckets)/sizeof(unsigned),
     .nchain = sizeof(gLibDlChains)/sizeof(unsigned),
     .bucket = gLibDlBuckets,
     .chain = gLibDlChains,

 #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,
 };
	/*
	* Copyright (C) 2007 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 "linker.h"

	#include <dlfcn.h>
	#include <pthread.h>
	#include <stdio.h>
	#include <stdlib.h>

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

	/* This file hijacks the symbols stubbed out in libdl.so. */

	static pthread_mutex_t gDlMutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER;

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

	const 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 != NULL) {
	strlcat(buffer, ": ", __BIONIC_DLERROR_BUFFER_SIZE);
	strlcat(buffer, detail, __BIONIC_DLERROR_BUFFER_SIZE);
	}

	__bionic_set_dlerror(buffer);
	}

	const char* dlerror() {
	const char* old_value = __bionic_set_dlerror(NULL);
	return old_value;
	}

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

	void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
	ScopedPthreadMutexLocker locker(&gDlMutex);
	do_android_update_LD_LIBRARY_PATH(ld_library_path);
	}

	void* dlopen(const char* filename, int flags) {
	ScopedPthreadMutexLocker locker(&gDlMutex);
	soinfo* result = do_dlopen(filename, flags);
	if (result == NULL) {
	__bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
	return NULL;
	}
	return result;
	}

	void* dlsym(void* handle, const char* symbol) {
	ScopedPthreadMutexLocker locker(&gDlMutex);

	if (handle == NULL) {
	__bionic_format_dlerror("dlsym library handle is null", NULL);
	return NULL;
	}
	if (symbol == NULL) {
	__bionic_format_dlerror("dlsym symbol name is null", NULL);
	return NULL;
	}

	soinfo* found = NULL;
	ElfW(Sym)* sym = NULL;
	if (handle == RTLD_DEFAULT) {
	sym = dlsym_linear_lookup(symbol, &found, NULL);
	} else if (handle == RTLD_NEXT) {
	void* ret_addr = __builtin_return_address(0);
	soinfo* si = find_containing_library(ret_addr);

	sym = NULL;
	if (si && si->next) {
	sym = dlsym_linear_lookup(symbol, &found, si->next);
	}
	} else {
	found = reinterpret_cast<soinfo*>(handle);
	sym = dlsym_handle_lookup(found, symbol);
	}

	if (sym != NULL) {
	unsigned bind = ELF_ST_BIND(sym->st_info);

	if (bind == STB_GLOBAL && sym->st_shndx != 0) {
	return reinterpret_cast<void*>(sym->st_value + found->load_bias);
	}

	__bionic_format_dlerror("symbol found but not global", symbol);
	return NULL;
	} else {
	__bionic_format_dlerror("undefined symbol", symbol);
	return NULL;
	}
	}

	int dladdr(const void* addr, Dl_info* info) {
	ScopedPthreadMutexLocker locker(&gDlMutex);

	// Determine if this address can be found in any library currently mapped.
	soinfo* si = find_containing_library(addr);
	if (si == NULL) {
	return 0;
	}

	memset(info, 0, sizeof(Dl_info));

	info->dli_fname = si->name;
	// Address at which the shared object is loaded.
	info->dli_fbase = (void*) si->base;

	// Determine if any symbol in the library contains the specified address.
	ElfW(Sym)* sym = dladdr_find_symbol(si, addr);
	if (sym != NULL) {
	info->dli_sname = si->strtab + sym->st_name;
	info->dli_saddr = (void*)(si->load_bias + sym->st_value);
	}

	return 1;
	}

	int dlclose(void* handle) {
	ScopedPthreadMutexLocker locker(&gDlMutex);
	return do_dlclose(reinterpret_cast<soinfo*>(handle));
	}

	// 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>(reinterpret_cast<void*>(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>(reinterpret_cast<void*>(value)), \
	/* st_size */ 0, \
	}

	#if defined(__arm__)
	// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
	// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
	# define ANDROID_LIBDL_STRTAB \
	"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0dl_unwind_find_exidx\0"
	#elif defined(__aarch64__) \|\| defined(__i386__) \|\| defined(__mips__) \|\| defined(__x86_64__)
	// 0000000 00011111 111112 22222222 2333333 3333444444444455555555556666666 6667777777777888888888899999 9999900000000001 1
	// 0123456 78901234 567890 12345678 9012345 6789012345678901234567890123456 7890123456789012345678901234 5678901234567890 1
	# define ANDROID_LIBDL_STRTAB \
	"dlopen\0dlclose\0dlsym\0dlerror\0dladdr\0android_update_LD_LIBRARY_PATH\0android_get_LD_LIBRARY_PATH\0dl_iterate_phdr\0"
	#else
	# error Unsupported architecture. Only arm, arm64, mips, mips64, x86 and x86_64 are presently supported.
	#endif

	static ElfW(Sym) gLibDlSymtab[] = {
	// 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, NULL, 0),
	ELFW(SYM_INITIALIZER)( 0, &dlopen, 1),
	ELFW(SYM_INITIALIZER)( 7, &dlclose, 1),
	ELFW(SYM_INITIALIZER)( 15, &dlsym, 1),
	ELFW(SYM_INITIALIZER)( 21, &dlerror, 1),
	ELFW(SYM_INITIALIZER)( 29, &dladdr, 1),
	ELFW(SYM_INITIALIZER)( 36, &android_update_LD_LIBRARY_PATH, 1),
	ELFW(SYM_INITIALIZER)( 67, &android_get_LD_LIBRARY_PATH, 1),
	ELFW(SYM_INITIALIZER)( 95, &dl_iterate_phdr, 1),
	#if defined(__arm__)
	ELFW(SYM_INITIALIZER)(111, &dl_unwind_find_exidx, 1),
	#endif
	};

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

	// This is used by the dynamic linker. Every process gets these symbols for free.
	soinfo libdl_info = {
	"libdl.so",

	.phdr = 0,
	.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 = gLibDlSymtab,

	.nbucket = sizeof(gLibDlBuckets)/sizeof(unsigned),
	.nchain = sizeof(gLibDlChains)/sizeof(unsigned),
	.bucket = gLibDlBuckets,
	.chain = gLibDlChains,

	#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,
	};