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Move dlsym and dladdr implementation to linker.cpp

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Bug: http://b/25716705
Bug: http://b/22865643
Change-Id: If22fc1eda219f676b5fcc06490f7901d21d1749c
This commit is contained in:
Dimitry Ivanov 2015-12-10 16:08:14 -08:00
parent 9d8632e1a7
commit 4a2c5aa30c
4 changed files with 137 additions and 96 deletions
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70
linker/dlfcn.cpp
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@ -16,12 +16,10 @@
#include "linker.h" #include "linker.h"
#include <dlfcn.h>
#include <pthread.h> #include <pthread.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
#include <string.h> #include <string.h>
#include <android/dlext.h>
#include <android/api-level.h> #include <android/api-level.h>
#include <bionic/pthread_internal.h> #include <bionic/pthread_internal.h>
@ -70,8 +68,7 @@ void android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
static void* dlopen_ext(const char* filename, int flags, static void* dlopen_ext(const char* filename, int flags,
const android_dlextinfo* extinfo, void* caller_addr) { const android_dlextinfo* extinfo, void* caller_addr) {
ScopedPthreadMutexLocker locker(&g_dl_mutex); ScopedPthreadMutexLocker locker(&g_dl_mutex);
soinfo* caller = find_containing_library(caller_addr); soinfo* result = do_dlopen(filename, flags, extinfo, caller_addr);
soinfo* result = do_dlopen(filename, flags, extinfo, caller);
if (result == nullptr) { if (result == nullptr) {
__bionic_format_dlerror("dlopen failed", linker_get_error_buffer()); __bionic_format_dlerror("dlopen failed", linker_get_error_buffer());
return nullptr; return nullptr;
@ -92,71 +89,20 @@ void* dlopen(const char* filename, int flags) {
extern android_namespace_t* g_anonymous_namespace; extern android_namespace_t* g_anonymous_namespace;
void* dlsym(void* handle, const char* symbol) { void* dlsym(void* handle, const char* symbol) {
ScopedPthreadMutexLocker locker(&g_dl_mutex);
// TODO(dimitry): move (most of) the code below to linker.cpp
#if !defined(__LP64__)
if (handle == nullptr) {
__bionic_format_dlerror("dlsym library handle is null", nullptr);
return nullptr;
}
#endif
if (symbol == nullptr) {
__bionic_format_dlerror("dlsym symbol name is null", nullptr);
return nullptr;
}
soinfo* found = nullptr;
const ElfW(Sym)* sym = nullptr;
void* caller_addr = __builtin_return_address(0); void* caller_addr = __builtin_return_address(0);
soinfo* caller = find_containing_library(caller_addr); ScopedPthreadMutexLocker locker(&g_dl_mutex);
android_namespace_t* ns = caller != nullptr ? caller->get_namespace() : g_anonymous_namespace; void* result;
if (!do_dlsym(handle, symbol, nullptr, caller_addr, &result)) {
if (handle == RTLD_DEFAULT || handle == RTLD_NEXT) { __bionic_format_dlerror(linker_get_error_buffer(), nullptr);
sym = dlsym_linear_lookup(ns, symbol, &found, caller, handle);
} else {
sym = dlsym_handle_lookup(reinterpret_cast<soinfo*>(handle), &found, symbol);
}
if (sym != nullptr) {
unsigned bind = ELF_ST_BIND(sym->st_info);
if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
return reinterpret_cast<void*>(found->resolve_symbol_address(sym));
}
__bionic_format_dlerror("symbol found but not global", symbol);
return nullptr;
} else {
__bionic_format_dlerror("undefined symbol", symbol);
return nullptr; return nullptr;
} }
return result;
} }
int dladdr(const void* addr, Dl_info* info) { int dladdr(const void* addr, Dl_info* info) {
ScopedPthreadMutexLocker locker(&g_dl_mutex); ScopedPthreadMutexLocker locker(&g_dl_mutex);
return do_dladdr(addr, info);
// Determine if this address can be found in any library currently mapped.
soinfo* si = find_containing_library(addr);
if (si == nullptr) {
return 0;
}
memset(info, 0, sizeof(Dl_info));
info->dli_fname = si->get_realpath();
// Address at which the shared object is loaded.
info->dli_fbase = reinterpret_cast<void*>(si->base);
// Determine if any symbol in the library contains the specified address.
ElfW(Sym)* sym = si->find_symbol_by_address(addr);
if (sym != nullptr) {
info->dli_sname = si->get_string(sym->st_name);
info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));
}
return 1;
} }
int dlclose(void* handle) { int dlclose(void* handle) {

130
linker/linker.cpp
View File

@ -27,7 +27,6 @@
*/ */
#include <android/api-level.h> #include <android/api-level.h>
#include <dlfcn.h>
#include <errno.h> #include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <inttypes.h> #include <inttypes.h>
@ -891,20 +890,23 @@ soinfo::soinfo(android_namespace_t* ns, const char* realpath,
this->namespace_ = ns; this->namespace_ = ns;
} }
static uint32_t calculate_elf_hash(const char* name) {
uint32_t SymbolName::elf_hash() { const uint8_t* name_bytes = reinterpret_cast<const uint8_t*>(name);
if (!has_elf_hash_) {
const uint8_t* name = reinterpret_cast<const uint8_t*>(name_);
uint32_t h = 0, g; uint32_t h = 0, g;
while (*name) { while (*name_bytes) {
h = (h << 4) + *name++; h = (h << 4) + *name_bytes++;
g = h & 0xf0000000; g = h & 0xf0000000;
h ^= g; h ^= g;
h ^= g >> 24; h ^= g >> 24;
} }
elf_hash_ = h; return h;
}
uint32_t SymbolName::elf_hash() {
if (!has_elf_hash_) {
elf_hash_ = calculate_elf_hash(name_);
has_elf_hash_ = true; has_elf_hash_ = true;
} }
@ -1243,7 +1245,8 @@ static bool walk_dependencies_tree(soinfo* root_soinfos[], size_t root_soinfos_s
static const ElfW(Sym)* dlsym_handle_lookup(soinfo* root, soinfo* skip_until, static const ElfW(Sym)* dlsym_handle_lookup(soinfo* root, soinfo* skip_until,
soinfo** found, SymbolName& symbol_name) { soinfo** found, SymbolName& symbol_name,
const version_info* vi) {
const ElfW(Sym)* result = nullptr; const ElfW(Sym)* result = nullptr;
bool skip_lookup = skip_until != nullptr; bool skip_lookup = skip_until != nullptr;
@ -1253,7 +1256,7 @@ static const ElfW(Sym)* dlsym_handle_lookup(soinfo* root, soinfo* skip_until,
return true; return true;
} }
if (!current_soinfo->find_symbol_by_name(symbol_name, nullptr, &result)) { if (!current_soinfo->find_symbol_by_name(symbol_name, vi, &result)) {
result = nullptr; result = nullptr;
return false; return false;
} }
@ -1269,9 +1272,17 @@ static const ElfW(Sym)* dlsym_handle_lookup(soinfo* root, soinfo* skip_until,
return result; return result;
} }
static const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns,
const char* name,
const version_info* vi,
soinfo** found,
soinfo* caller,
void* handle);
// This is used by dlsym(3). It performs symbol lookup only within the // This is used by dlsym(3). It performs symbol lookup only within the
// specified soinfo object and its dependencies in breadth first order. // specified soinfo object and its dependencies in breadth first order.
const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) { static const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found,
const char* name, const version_info* vi) {
// According to man dlopen(3) and posix docs in the case when si is handle // According to man dlopen(3) and posix docs in the case when si is handle
// of the main executable we need to search not only in the executable and its // of the main executable we need to search not only in the executable and its
// dependencies but also in all libraries loaded with RTLD_GLOBAL. // dependencies but also in all libraries loaded with RTLD_GLOBAL.
@ -1280,11 +1291,11 @@ const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* nam
// libraries and they are loaded in breath-first (correct) order we can just execute // libraries and they are loaded in breath-first (correct) order we can just execute
// dlsym(RTLD_DEFAULT, ...); instead of doing two stage lookup. // dlsym(RTLD_DEFAULT, ...); instead of doing two stage lookup.
if (si == somain) { if (si == somain) {
return dlsym_linear_lookup(&g_default_namespace, name, found, nullptr, RTLD_DEFAULT); return dlsym_linear_lookup(&g_default_namespace, name, vi, found, nullptr, RTLD_DEFAULT);
} }
SymbolName symbol_name(name); SymbolName symbol_name(name);
return dlsym_handle_lookup(si, nullptr, found, symbol_name); return dlsym_handle_lookup(si, nullptr, found, symbol_name, vi);
} }
/* This is used by dlsym(3) to performs a global symbol lookup. If the /* This is used by dlsym(3) to performs a global symbol lookup. If the
@ -1292,8 +1303,9 @@ const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* nam
beginning of the global solist. Otherwise the search starts at the beginning of the global solist. Otherwise the search starts at the
specified soinfo (for RTLD_NEXT). specified soinfo (for RTLD_NEXT).
*/ */
const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns, static const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns,
const char* name, const char* name,
const version_info* vi,
soinfo** found, soinfo** found,
soinfo* caller, soinfo* caller,
void* handle) { void* handle) {
@ -1322,7 +1334,7 @@ const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns,
continue; continue;
} }
if (!si->find_symbol_by_name(symbol_name, nullptr, &s)) { if (!si->find_symbol_by_name(symbol_name, vi, &s)) {
return nullptr; return nullptr;
} }
@ -1338,7 +1350,7 @@ const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns,
if (s == nullptr && caller != nullptr && if (s == nullptr && caller != nullptr &&
(caller->get_rtld_flags() & RTLD_GLOBAL) == 0) { (caller->get_rtld_flags() & RTLD_GLOBAL) == 0) {
return dlsym_handle_lookup(caller->get_local_group_root(), return dlsym_handle_lookup(caller->get_local_group_root(),
(handle == RTLD_NEXT) ? caller : nullptr, found, symbol_name); (handle == RTLD_NEXT) ? caller : nullptr, found, symbol_name, vi);
} }
if (s != nullptr) { if (s != nullptr) {
@ -2176,6 +2188,14 @@ static void soinfo_unload(soinfo* root) {
} }
} }
static std::string symbol_display_name(const char* sym_name, const char* sym_ver) {
if (sym_ver == nullptr) {
return sym_name;
}
return std::string(sym_name) + "@" + sym_ver;
}
void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) { void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
// Use basic string manipulation calls to avoid snprintf. // Use basic string manipulation calls to avoid snprintf.
// snprintf indirectly calls pthread_getspecific to get the size of a buffer. // snprintf indirectly calls pthread_getspecific to get the size of a buffer.
@ -2203,7 +2223,10 @@ void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
parse_LD_LIBRARY_PATH(ld_library_path); parse_LD_LIBRARY_PATH(ld_library_path);
} }
soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo, soinfo *caller) { soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo,
void* caller_addr) {
soinfo* const caller = find_containing_library(caller_addr);
if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) { if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
DL_ERR("invalid flags to dlopen: %x", flags); DL_ERR("invalid flags to dlopen: %x", flags);
return nullptr; return nullptr;
@ -2249,6 +2272,79 @@ soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo,
return si; return si;
} }
int do_dladdr(const void* addr, Dl_info* info) {
// Determine if this address can be found in any library currently mapped.
soinfo* si = find_containing_library(addr);
if (si == nullptr) {
return 0;
}
memset(info, 0, sizeof(Dl_info));
info->dli_fname = si->get_realpath();
// Address at which the shared object is loaded.
info->dli_fbase = reinterpret_cast<void*>(si->base);
// Determine if any symbol in the library contains the specified address.
ElfW(Sym)* sym = si->find_symbol_by_address(addr);
if (sym != nullptr) {
info->dli_sname = si->get_string(sym->st_name);
info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));
}
return 1;
}
bool do_dlsym(void* handle, const char* sym_name, const char* sym_ver,
void* caller_addr, void** symbol) {
#if !defined(__LP64__)
if (handle == nullptr) {
DL_ERR("dlsym failed: library handle is null");
return false;
}
#endif
if (sym_name == nullptr) {
DL_ERR("dlsym failed: symbol name is null");
return false;
}
soinfo* found = nullptr;
const ElfW(Sym)* sym = nullptr;
soinfo* caller = find_containing_library(caller_addr);
android_namespace_t* ns = caller != nullptr ? caller->get_namespace() : g_anonymous_namespace;
version_info vi_instance;
version_info* vi = nullptr;
if (sym_ver != nullptr) {
vi_instance.name = sym_name;
vi_instance.elf_hash = calculate_elf_hash(sym_name);
vi = &vi_instance;
}
if (handle == RTLD_DEFAULT || handle == RTLD_NEXT) {
sym = dlsym_linear_lookup(ns, sym_name, vi, &found, caller, handle);
} else {
sym = dlsym_handle_lookup(reinterpret_cast<soinfo*>(handle), &found, sym_name, vi);
}
if (sym != nullptr) {
uint32_t bind = ELF_ST_BIND(sym->st_info);
if ((bind == STB_GLOBAL || bind == STB_WEAK) && sym->st_shndx != 0) {
*symbol = reinterpret_cast<void*>(found->resolve_symbol_address(sym));
return true;
}
DL_ERR("symbol \"%s\" found but not global", symbol_display_name(sym_name, sym_ver).c_str());
return false;
}
DL_ERR("undefined symbol: %s", symbol_display_name(sym_name, sym_ver).c_str());
return false;
}
void do_dlclose(soinfo* si) { void do_dlclose(soinfo* si) {
ProtectedDataGuard guard; ProtectedDataGuard guard;
soinfo_unload(si); soinfo_unload(si);

13
linker/linker.h
View File

@ -29,6 +29,7 @@
#ifndef _LINKER_H_ #ifndef _LINKER_H_
#define _LINKER_H_ #define _LINKER_H_
#include <dlfcn.h>
#include <android/dlext.h> #include <android/dlext.h>
#include <elf.h> #include <elf.h>
#include <inttypes.h> #include <inttypes.h>
@ -135,7 +136,7 @@ class SymbolName {
}; };
struct version_info { struct version_info {
version_info() : elf_hash(0), name(nullptr), target_si(nullptr) {} constexpr version_info() : elf_hash(0), name(nullptr), target_si(nullptr) {}
uint32_t elf_hash; uint32_t elf_hash;
const char* name; const char* name;
@ -422,17 +423,15 @@ soinfo* get_libdl_info();
void do_android_get_LD_LIBRARY_PATH(char*, size_t); void do_android_get_LD_LIBRARY_PATH(char*, size_t);
void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path); void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path);
soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo, soinfo *caller); soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo, void* caller_addr);
void do_dlclose(soinfo* si); void do_dlclose(soinfo* si);
int do_dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data); int do_dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data);
const ElfW(Sym)* dlsym_linear_lookup(android_namespace_t* ns, const char* name, soinfo** found, bool do_dlsym(void* handle, const char* sym_name, const char* sym_ver,
soinfo* caller, void* handle); void* caller_addr, void** symbol);
soinfo* find_containing_library(const void* addr); int do_dladdr(const void* addr, Dl_info* info);
const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);
void debuggerd_init(); void debuggerd_init();
extern "C" abort_msg_t* g_abort_message; extern "C" abort_msg_t* g_abort_message;

4
tests/dlfcn_test.cpp
View File

@ -760,7 +760,7 @@ TEST(dlfcn, dlsym_failures) {
// so it can be distinguished from the NULL handle. // so it can be distinguished from the NULL handle.
sym = dlsym(nullptr, "test"); sym = dlsym(nullptr, "test");
ASSERT_TRUE(sym == nullptr); ASSERT_TRUE(sym == nullptr);
ASSERT_SUBSTR("dlsym library handle is null", dlerror()); ASSERT_STREQ("dlsym failed: library handle is null", dlerror());
#endif #endif
// NULL symbol name. // NULL symbol name.
@ -768,7 +768,7 @@ TEST(dlfcn, dlsym_failures) {
// glibc marks this parameter non-null and SEGVs if you cheat. // glibc marks this parameter non-null and SEGVs if you cheat.
sym = dlsym(self, nullptr); sym = dlsym(self, nullptr);
ASSERT_TRUE(sym == nullptr); ASSERT_TRUE(sym == nullptr);
ASSERT_SUBSTR("", dlerror()); ASSERT_STREQ("dlsym failed: symbol name is null", dlerror());
#endif #endif
// Symbol that doesn't exist. // Symbol that doesn't exist.