tequilaOS/platform_bionic
2
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity
platform_bionic/linker/linker.cpp
Dmitriy Ivanov b4e5067cab linker: initialize system properties 
Bug: http://b/20567629
Bug: https://code.google.com/p/chromium/issues/detail?id=478886
Change-Id: I8d2d89b749015e7fcd6e7ea646911f2e617dd1ba
2015-04-28 15:52:52 -07:00

3329 lines
99 KiB
C++
Raw Blame History

/*
* 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.
*/
#include <dlfcn.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <sys/personality.h>
#include <unistd.h>
#include <new>
#include <string>
#include <vector>
// Private C library headers.
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
#include "private/ScopedPthreadMutexLocker.h"
#include "private/ScopedFd.h"
#include "private/ScopeGuard.h"
#include "private/UniquePtr.h"
#include "linker.h"
#include "linker_block_allocator.h"
#include "linker_debug.h"
#include "linker_environ.h"
#include "linker_sleb128.h"
#include "linker_phdr.h"
#include "linker_relocs.h"
#include "linker_reloc_iterators.h"
#include "ziparchive/zip_archive.h"
// Override macros to use C++ style casts
#undef ELF_ST_TYPE
#define ELF_ST_TYPE(x) (static_cast<uint32_t>(x) & 0xf)
static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
static LinkerTypeAllocator<soinfo> g_soinfo_allocator;
static LinkerTypeAllocator<LinkedListEntry<soinfo>> g_soinfo_links_allocator;
static soinfo* solist;
static soinfo* sonext;
static soinfo* somain; // main process, always the one after libdl_info
static const char* const kDefaultLdPaths[] = {
#if defined(__LP64__)
"/vendor/lib64",
"/system/lib64",
#else
"/vendor/lib",
"/system/lib",
#endif
nullptr
};
static const ElfW(Versym) kVersymNotNeeded = 0;
static const ElfW(Versym) kVersymGlobal = 1;
static std::vector<std::string> g_ld_library_paths;
static std::vector<std::string> g_ld_preload_names;
static std::vector<soinfo*> g_ld_preloads;
__LIBC_HIDDEN__ int g_ld_debug_verbosity;
__LIBC_HIDDEN__ abort_msg_t* g_abort_message = nullptr; // For debuggerd.
#if STATS
struct linker_stats_t {
int count[kRelocMax];
};
static linker_stats_t linker_stats;
void count_relocation(RelocationKind kind) {
++linker_stats.count[kind];
}
#else
void count_relocation(RelocationKind) {
}
#endif
#if COUNT_PAGES
uint32_t bitmask[4096];
#endif
static char __linker_dl_err_buf[768];
char* linker_get_error_buffer() {
return &__linker_dl_err_buf[0];
}
size_t linker_get_error_buffer_size() {
return sizeof(__linker_dl_err_buf);
}
// This function is an empty stub where GDB locates a breakpoint to get notified
// about linker activity.
extern "C"
void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity();
static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER;
static r_debug _r_debug =
{1, nullptr, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0};
static link_map* r_debug_tail = 0;
static void insert_soinfo_into_debug_map(soinfo* info) {
// Copy the necessary fields into the debug structure.
link_map* map = &(info->link_map_head);
map->l_addr = info->load_bias;
// link_map l_name field is not const.
map->l_name = const_cast<char*>(info->get_realpath());
map->l_ld = info->dynamic;
// Stick the new library at the end of the list.
// gdb tends to care more about libc than it does
// about leaf libraries, and ordering it this way
// reduces the back-and-forth over the wire.
if (r_debug_tail) {
r_debug_tail->l_next = map;
map->l_prev = r_debug_tail;
map->l_next = 0;
} else {
_r_debug.r_map = map;
map->l_prev = 0;
map->l_next = 0;
}
r_debug_tail = map;
}
static void remove_soinfo_from_debug_map(soinfo* info) {
link_map* map = &(info->link_map_head);
if (r_debug_tail == map) {
r_debug_tail = map->l_prev;
}
if (map->l_prev) {
map->l_prev->l_next = map->l_next;
}
if (map->l_next) {
map->l_next->l_prev = map->l_prev;
}
}
static void notify_gdb_of_load(soinfo* info) {
if (info->is_main_executable()) {
// GDB already knows about the main executable
return;
}
ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
_r_debug.r_state = r_debug::RT_ADD;
rtld_db_dlactivity();
insert_soinfo_into_debug_map(info);
_r_debug.r_state = r_debug::RT_CONSISTENT;
rtld_db_dlactivity();
}
static void notify_gdb_of_unload(soinfo* info) {
if (info->is_main_executable()) {
// GDB already knows about the main executable
return;
}
ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
_r_debug.r_state = r_debug::RT_DELETE;
rtld_db_dlactivity();
remove_soinfo_from_debug_map(info);
_r_debug.r_state = r_debug::RT_CONSISTENT;
rtld_db_dlactivity();
}
void notify_gdb_of_libraries() {
_r_debug.r_state = r_debug::RT_ADD;
rtld_db_dlactivity();
_r_debug.r_state = r_debug::RT_CONSISTENT;
rtld_db_dlactivity();
}
LinkedListEntry<soinfo>* SoinfoListAllocator::alloc() {
return g_soinfo_links_allocator.alloc();
}
void SoinfoListAllocator::free(LinkedListEntry<soinfo>* entry) {
g_soinfo_links_allocator.free(entry);
}
static soinfo* soinfo_alloc(const char* name, struct stat* file_stat,
off64_t file_offset, uint32_t rtld_flags) {
if (strlen(name) >= PATH_MAX) {
DL_ERR("library name \"%s\" too long", name);
return nullptr;
}
soinfo* si = new (g_soinfo_allocator.alloc()) soinfo(name, file_stat, file_offset, rtld_flags);
sonext->next = si;
sonext = si;
TRACE("name %s: allocated soinfo @ %p", name, si);
return si;
}
static void soinfo_free(soinfo* si) {
if (si == nullptr) {
return;
}
if (si->base != 0 && si->size != 0) {
munmap(reinterpret_cast<void*>(si->base), si->size);
}
soinfo *prev = nullptr, *trav;
TRACE("name %s: freeing soinfo @ %p", si->get_soname(), si);
for (trav = solist; trav != nullptr; trav = trav->next) {
if (trav == si) {
break;
}
prev = trav;
}
if (trav == nullptr) {
// si was not in solist
DL_ERR("name \"%s\"@%p is not in solist!", si->get_soname(), si);
return;
}
// clear links to/from si
si->remove_all_links();
// prev will never be null, because the first entry in solist is
// always the static libdl_info.
prev->next = si->next;
if (si == sonext) {
sonext = prev;
}
g_soinfo_allocator.free(si);
}
static void parse_path(const char* path, const char* delimiters,
std::vector<std::string>* paths) {
if (path == nullptr) {
return;
}
paths->clear();
for (const char *p = path; ; ++p) {
size_t len = strcspn(p, delimiters);
// skip empty tokens
if (len == 0) {
continue;
}
paths->push_back(std::string(p, len));
p += len;
if (*p == '\0') {
break;
}
}
}
static void parse_LD_LIBRARY_PATH(const char* path) {
parse_path(path, ":", &g_ld_library_paths);
}
static void parse_LD_PRELOAD(const char* path) {
// We have historically supported ':' as well as ' ' in LD_PRELOAD.
parse_path(path, " :", &g_ld_preload_names);
}
static bool realpath_fd(int fd, std::string* realpath) {
std::vector<char> buf(PATH_MAX), proc_self_fd(PATH_MAX);
snprintf(&proc_self_fd[0], proc_self_fd.size(), "/proc/self/fd/%d", fd);
if (readlink(&proc_self_fd[0], &buf[0], buf.size()) == -1) {
return false;
}
*realpath = std::string(&buf[0]);
return true;
}
#if defined(__arm__)
// For a given PC, find the .so that it belongs to.
// Returns the base address of the .ARM.exidx section
// for that .so, and the number of 8-byte entries
// in that section (via *pcount).
//
// Intended to be called by libc's __gnu_Unwind_Find_exidx().
//
// This function is exposed via dlfcn.cpp and libdl.so.
_Unwind_Ptr dl_unwind_find_exidx(_Unwind_Ptr pc, int* pcount) {
uintptr_t addr = reinterpret_cast<uintptr_t>(pc);
for (soinfo* si = solist; si != 0; si = si->next) {
if ((addr >= si->base) && (addr < (si->base + si->size))) {
*pcount = si->ARM_exidx_count;
return reinterpret_cast<_Unwind_Ptr>(si->ARM_exidx);
}
}
*pcount = 0;
return nullptr;
}
#endif
// Here, we only have to provide a callback to iterate across all the
// loaded libraries. gcc_eh does the rest.
int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void* data) {
int rv = 0;
for (soinfo* si = solist; si != nullptr; si = si->next) {
dl_phdr_info dl_info;
dl_info.dlpi_addr = si->link_map_head.l_addr;
dl_info.dlpi_name = si->link_map_head.l_name;
dl_info.dlpi_phdr = si->phdr;
dl_info.dlpi_phnum = si->phnum;
rv = cb(&dl_info, sizeof(dl_phdr_info), data);
if (rv != 0) {
break;
}
}
return rv;
}
const ElfW(Versym)* soinfo::get_versym(size_t n) const {
if (has_min_version(2) && versym_ != nullptr) {
return versym_ + n;
}
return nullptr;
}
ElfW(Addr) soinfo::get_verneed_ptr() const {
if (has_min_version(2)) {
return verneed_ptr_;
}
return 0;
}
size_t soinfo::get_verneed_cnt() const {
if (has_min_version(2)) {
return verneed_cnt_;
}
return 0;
}
ElfW(Addr) soinfo::get_verdef_ptr() const {
if (has_min_version(2)) {
return verdef_ptr_;
}
return 0;
}
size_t soinfo::get_verdef_cnt() const {
if (has_min_version(2)) {
return verdef_cnt_;
}
return 0;
}
template<typename F>
static bool for_each_verdef(const soinfo* si, F functor) {
if (!si->has_min_version(2)) {
return true;
}
uintptr_t verdef_ptr = si->get_verdef_ptr();
if (verdef_ptr == 0) {
return true;
}
size_t offset = 0;
size_t verdef_cnt = si->get_verdef_cnt();
for (size_t i = 0; i<verdef_cnt; ++i) {
const ElfW(Verdef)* verdef = reinterpret_cast<ElfW(Verdef)*>(verdef_ptr + offset);
size_t verdaux_offset = offset + verdef->vd_aux;
offset += verdef->vd_next;
if (verdef->vd_version != 1) {
DL_ERR("unsupported verdef[%zd] vd_version: %d (expected 1) library: %s",
i, verdef->vd_version, si->get_soname());
return false;
}
if ((verdef->vd_flags & VER_FLG_BASE) != 0) {
// "this is the version of the file itself. It must not be used for
// matching a symbol. It can be used to match references."
//
// http://www.akkadia.org/drepper/symbol-versioning
continue;
}
if (verdef->vd_cnt == 0) {
DL_ERR("invalid verdef[%zd] vd_cnt == 0 (version without a name)", i);
return false;
}
const ElfW(Verdaux)* verdaux = reinterpret_cast<ElfW(Verdaux)*>(verdef_ptr + verdaux_offset);
if (functor(i, verdef, verdaux) == true) {
break;
}
}
return true;
}
bool soinfo::find_verdef_version_index(const version_info* vi, ElfW(Versym)* versym) const {
if (vi == nullptr) {
*versym = kVersymNotNeeded;
return true;
}
*versym = kVersymGlobal;
return for_each_verdef(this,
[&](size_t, const ElfW(Verdef)* verdef, const ElfW(Verdaux)* verdaux) {
if (verdef->vd_hash == vi->elf_hash &&
strcmp(vi->name, get_string(verdaux->vda_name)) == 0) {
*versym = verdef->vd_ndx;
return true;
}
return false;
}
);
}
bool soinfo::find_symbol_by_name(SymbolName& symbol_name,
const version_info* vi,
const ElfW(Sym)** symbol) const {
uint32_t symbol_index;
bool success =
is_gnu_hash() ?
gnu_lookup(symbol_name, vi, &symbol_index) :
elf_lookup(symbol_name, vi, &symbol_index);
if (success) {
*symbol = symbol_index == 0 ? nullptr : symtab_ + symbol_index;
}
return success;
}
static bool is_symbol_global_and_defined(const soinfo* si, const ElfW(Sym)* s) {
if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
ELF_ST_BIND(s->st_info) == STB_WEAK) {
return s->st_shndx != SHN_UNDEF;
} else if (ELF_ST_BIND(s->st_info) != STB_LOCAL) {
DL_WARN("unexpected ST_BIND value: %d for '%s' in '%s'",
ELF_ST_BIND(s->st_info), si->get_string(s->st_name), si->get_soname());
}
return false;
}
static const ElfW(Versym) kVersymHiddenBit = 0x8000;
static inline bool is_versym_hidden(const ElfW(Versym)* versym) {
// the symbol is hidden if bit 15 of versym is set.
return versym != nullptr && (*versym & kVersymHiddenBit) != 0;
}
static inline bool check_symbol_version(const ElfW(Versym) verneed,
const ElfW(Versym)* verdef) {
return verneed == kVersymNotNeeded ||
verdef == nullptr ||
verneed == (*verdef & ~kVersymHiddenBit);
}
bool soinfo::gnu_lookup(SymbolName& symbol_name,
const version_info* vi,
uint32_t* symbol_index) const {
uint32_t hash = symbol_name.gnu_hash();
uint32_t h2 = hash >> gnu_shift2_;
uint32_t bloom_mask_bits = sizeof(ElfW(Addr))*8;
uint32_t word_num = (hash / bloom_mask_bits) & gnu_maskwords_;
ElfW(Addr) bloom_word = gnu_bloom_filter_[word_num];
*symbol_index = 0;
TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p (gnu)",
symbol_name.get_name(), get_soname(), reinterpret_cast<void*>(base));
// test against bloom filter
if ((1 & (bloom_word >> (hash % bloom_mask_bits)) & (bloom_word >> (h2 % bloom_mask_bits))) == 0) {
TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p",
symbol_name.get_name(), get_soname(), reinterpret_cast<void*>(base));
return true;
}
// bloom test says "probably yes"...
uint32_t n = gnu_bucket_[hash % gnu_nbucket_];
if (n == 0) {
TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p",
symbol_name.get_name(), get_soname(), reinterpret_cast<void*>(base));
return true;
}
// lookup versym for the version definition in this library
// note the difference between "version is not requested" (vi == nullptr)
// and "version not found". In the first case verneed is kVersymNotNeeded
// which implies that the default version can be accepted; the second case results in
// verneed = 1 (kVersymGlobal) and implies that we should ignore versioned symbols
// for this library and consider only *global* ones.
ElfW(Versym) verneed = 0;
if (!find_verdef_version_index(vi, &verneed)) {
return false;
}
do {
ElfW(Sym)* s = symtab_ + n;
const ElfW(Versym)* verdef = get_versym(n);
// skip hidden versions when verneed == kVersymNotNeeded (0)
if (verneed == kVersymNotNeeded && is_versym_hidden(verdef)) {
continue;
}
if (((gnu_chain_[n] ^ hash) >> 1) == 0 &&
check_symbol_version(verneed, verdef) &&
strcmp(get_string(s->st_name), symbol_name.get_name()) == 0 &&
is_symbol_global_and_defined(this, s)) {
TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
symbol_name.get_name(), get_soname(), reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
*symbol_index = n;
return true;
}
} while ((gnu_chain_[n++] & 1) == 0);
TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p",
symbol_name.get_name(), get_soname(), reinterpret_cast<void*>(base));
return true;
}
bool soinfo::elf_lookup(SymbolName& symbol_name,
const version_info* vi,
uint32_t* symbol_index) const {
uint32_t hash = symbol_name.elf_hash();
TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p h=%x(elf) %zd",
symbol_name.get_name(), get_soname(),
reinterpret_cast<void*>(base), hash, hash % nbucket_);
ElfW(Versym) verneed = 0;
if (!find_verdef_version_index(vi, &verneed)) {
return false;
}
for (uint32_t n = bucket_[hash % nbucket_]; n != 0; n = chain_[n]) {
ElfW(Sym)* s = symtab_ + n;
const ElfW(Versym)* verdef = get_versym(n);
// skip hidden versions when verneed == 0
if (verneed == kVersymNotNeeded && is_versym_hidden(verdef)) {
continue;
}
if (check_symbol_version(verneed, verdef) &&
strcmp(get_string(s->st_name), symbol_name.get_name()) == 0 &&
is_symbol_global_and_defined(this, s)) {
TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
symbol_name.get_name(), get_soname(),
reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
*symbol_index = n;
return true;
}
}
TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd",
symbol_name.get_name(), get_soname(),
reinterpret_cast<void*>(base), hash, hash % nbucket_);
*symbol_index = 0;
return true;
}
soinfo::soinfo(const char* realpath, const struct stat* file_stat,
off64_t file_offset, int rtld_flags) {
memset(this, 0, sizeof(*this));
if (realpath != nullptr) {
realpath_ = realpath;
}
flags_ = FLAG_NEW_SOINFO;
version_ = SOINFO_VERSION;
if (file_stat != nullptr) {
this->st_dev_ = file_stat->st_dev;
this->st_ino_ = file_stat->st_ino;
this->file_offset_ = file_offset;
}
this->rtld_flags_ = rtld_flags;
}
uint32_t SymbolName::elf_hash() {
if (!has_elf_hash_) {
const uint8_t* name = reinterpret_cast<const uint8_t*>(name_);
uint32_t h = 0, g;
while (*name) {
h = (h << 4) + *name++;
g = h & 0xf0000000;
h ^= g;
h ^= g >> 24;
}
elf_hash_ = h;
has_elf_hash_ = true;
}
return elf_hash_;
}
uint32_t SymbolName::gnu_hash() {
if (!has_gnu_hash_) {
uint32_t h = 5381;
const uint8_t* name = reinterpret_cast<const uint8_t*>(name_);
while (*name != 0) {
h += (h << 5) + *name++; // h*33 + c = h + h * 32 + c = h + h << 5 + c
}
gnu_hash_ = h;
has_gnu_hash_ = true;
}
return gnu_hash_;
}
bool soinfo_do_lookup(soinfo* si_from, const char* name, const version_info* vi,
soinfo** si_found_in, const soinfo::soinfo_list_t& global_group,
const soinfo::soinfo_list_t& local_group, const ElfW(Sym)** symbol) {
SymbolName symbol_name(name);
const ElfW(Sym)* s = nullptr;
/* "This element's presence in a shared object library alters the dynamic linker's
* symbol resolution algorithm for references within the library. Instead of starting
* a symbol search with the executable file, the dynamic linker starts from the shared
* object itself. If the shared object fails to supply the referenced symbol, the
* dynamic linker then searches the executable file and other shared objects as usual."
*
* http://www.sco.com/developers/gabi/2012-12-31/ch5.dynamic.html
*
* Note that this is unlikely since static linker avoids generating
* relocations for -Bsymbolic linked dynamic executables.
*/
if (si_from->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si_from->get_soname(), name);
if (!si_from->find_symbol_by_name(symbol_name, vi, &s)) {
return false;
}
if (s != nullptr) {
*si_found_in = si_from;
}
}
// 1. Look for it in global_group
if (s == nullptr) {
bool error = false;
global_group.visit([&](soinfo* global_si) {
DEBUG("%s: looking up %s in %s (from global group)",
si_from->get_soname(), name, global_si->get_soname());
if (!global_si->find_symbol_by_name(symbol_name, vi, &s)) {
error = true;
return false;
}
if (s != nullptr) {
*si_found_in = global_si;
return false;
}
return true;
});
if (error) {
return false;
}
}
// 2. Look for it in the local group
if (s == nullptr) {
bool error = false;
local_group.visit([&](soinfo* local_si) {
if (local_si == si_from && si_from->has_DT_SYMBOLIC) {
// we already did this - skip
return true;
}
DEBUG("%s: looking up %s in %s (from local group)",
si_from->get_soname(), name, local_si->get_soname());
if (!local_si->find_symbol_by_name(symbol_name, vi, &s)) {
error = true;
return false;
}
if (s != nullptr) {
*si_found_in = local_si;
return false;
}
return true;
});
if (error) {
return false;
}
}
if (s != nullptr) {
TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
"found in %s, base = %p, load bias = %p",
si_from->get_soname(), name, reinterpret_cast<void*>(s->st_value),
(*si_found_in)->get_soname(), reinterpret_cast<void*>((*si_found_in)->base),
reinterpret_cast<void*>((*si_found_in)->load_bias));
}
*symbol = s;
return true;
}
class ProtectedDataGuard {
public:
ProtectedDataGuard() {
if (ref_count_++ == 0) {
protect_data(PROT_READ | PROT_WRITE);
}
}
~ProtectedDataGuard() {
if (ref_count_ == 0) { // overflow
__libc_fatal("Too many nested calls to dlopen()");
}
if (--ref_count_ == 0) {
protect_data(PROT_READ);
}
}
private:
void protect_data(int protection) {
g_soinfo_allocator.protect_all(protection);
g_soinfo_links_allocator.protect_all(protection);
}
static size_t ref_count_;
};
size_t ProtectedDataGuard::ref_count_ = 0;
// Each size has it's own allocator.
template<size_t size>
class SizeBasedAllocator {
public:
static void* alloc() {
return allocator_.alloc();
}
static void free(void* ptr) {
allocator_.free(ptr);
}
private:
static LinkerBlockAllocator allocator_;
};
template<size_t size>
LinkerBlockAllocator SizeBasedAllocator<size>::allocator_(size);
template<typename T>
class TypeBasedAllocator {
public:
static T* alloc() {
return reinterpret_cast<T*>(SizeBasedAllocator<sizeof(T)>::alloc());
}
static void free(T* ptr) {
SizeBasedAllocator<sizeof(T)>::free(ptr);
}
};
class LoadTask {
public:
struct deleter_t {
void operator()(LoadTask* t) {
TypeBasedAllocator<LoadTask>::free(t);
}
};
typedef UniquePtr<LoadTask, deleter_t> unique_ptr;
static deleter_t deleter;
static LoadTask* create(const char* name, soinfo* needed_by) {
LoadTask* ptr = TypeBasedAllocator<LoadTask>::alloc();
return new (ptr) LoadTask(name, needed_by);
}
const char* get_name() const {
return name_;
}
soinfo* get_needed_by() const {
return needed_by_;
}
private:
LoadTask(const char* name, soinfo* needed_by)
: name_(name), needed_by_(needed_by) {}
const char* name_;
soinfo* needed_by_;
DISALLOW_IMPLICIT_CONSTRUCTORS(LoadTask);
};
LoadTask::deleter_t LoadTask::deleter;
template <typename T>
using linked_list_t = LinkedList<T, TypeBasedAllocator<LinkedListEntry<T>>>;
typedef linked_list_t<soinfo> SoinfoLinkedList;
typedef linked_list_t<const char> StringLinkedList;
typedef linked_list_t<LoadTask> LoadTaskList;
// This function walks down the tree of soinfo dependencies
// in breadth-first order and
// * calls action(soinfo* si) for each node, and
// * terminates walk if action returns false.
//
// walk_dependencies_tree returns false if walk was terminated
// by the action and true otherwise.
template<typename F>
static bool walk_dependencies_tree(soinfo* root_soinfos[], size_t root_soinfos_size, F action) {
SoinfoLinkedList visit_list;
SoinfoLinkedList visited;
for (size_t i = 0; i < root_soinfos_size; ++i) {
visit_list.push_back(root_soinfos[i]);
}
soinfo* si;
while ((si = visit_list.pop_front()) != nullptr) {
if (visited.contains(si)) {
continue;
}
if (!action(si)) {
return false;
}
visited.push_back(si);
si->get_children().for_each([&](soinfo* child) {
visit_list.push_back(child);
});
}
return true;
}
// This is used by dlsym(3). It performs symbol lookup only within the
// specified soinfo object and its dependencies in breadth first order.
const ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
const ElfW(Sym)* result = nullptr;
SymbolName symbol_name(name);
walk_dependencies_tree(&si, 1, [&](soinfo* current_soinfo) {
if (!current_soinfo->find_symbol_by_name(symbol_name, nullptr, &result)) {
result = nullptr;
return false;
}
if (result != nullptr) {
*found = current_soinfo;
return false;
}
return true;
});
return result;
}
/* This is used by dlsym(3) to performs a global symbol lookup. If the
start value is null (for RTLD_DEFAULT), the search starts at the
beginning of the global solist. Otherwise the search starts at the
specified soinfo (for RTLD_NEXT).
*/
const ElfW(Sym)* dlsym_linear_lookup(const char* name,
soinfo** found,
soinfo* caller,
void* handle) {
SymbolName symbol_name(name);
soinfo* start = solist;
if (handle == RTLD_NEXT) {
if (caller == nullptr || caller->next == nullptr) {
return nullptr;
} else {
start = caller->next;
}
}
const ElfW(Sym)* s = nullptr;
for (soinfo* si = start; si != nullptr; si = si->next) {
if ((si->get_rtld_flags() & RTLD_GLOBAL) == 0) {
continue;
}
if (!si->find_symbol_by_name(symbol_name, nullptr, &s)) {
return nullptr;
}
if (s != nullptr) {
*found = si;
break;
}
}
// If not found - look into local_group unless
// caller is part of the global group in which
// case we already did it.
if (s == nullptr && caller != nullptr &&
(caller->get_rtld_flags() & RTLD_GLOBAL) == 0) {
soinfo* local_group_root = caller->get_local_group_root();
if (handle == RTLD_DEFAULT) {
start = local_group_root;
}
for (soinfo* si = start; si != nullptr; si = si->next) {
if (si->get_local_group_root() != local_group_root) {
break;
}
if (!si->find_symbol_by_name(symbol_name, nullptr, &s)) {
return nullptr;
}
if (s != nullptr) {
*found = si;
break;
}
}
}
if (s != nullptr) {
TRACE_TYPE(LOOKUP, "%s s->st_value = %p, found->base = %p",
name, reinterpret_cast<void*>(s->st_value), reinterpret_cast<void*>((*found)->base));
}
return s;
}
soinfo* find_containing_library(const void* p) {
ElfW(Addr) address = reinterpret_cast<ElfW(Addr)>(p);
for (soinfo* si = solist; si != nullptr; si = si->next) {
if (address >= si->base && address - si->base < si->size) {
return si;
}
}
return nullptr;
}
ElfW(Sym)* soinfo::find_symbol_by_address(const void* addr) {
return is_gnu_hash() ? gnu_addr_lookup(addr) : elf_addr_lookup(addr);
}
static bool symbol_matches_soaddr(const ElfW(Sym)* sym, ElfW(Addr) soaddr) {
return sym->st_shndx != SHN_UNDEF &&
soaddr >= sym->st_value &&
soaddr < sym->st_value + sym->st_size;
}
ElfW(Sym)* soinfo::gnu_addr_lookup(const void* addr) {
ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - load_bias;
for (size_t i = 0; i < gnu_nbucket_; ++i) {
uint32_t n = gnu_bucket_[i];
if (n == 0) {
continue;
}
do {
ElfW(Sym)* sym = symtab_ + n;
if (symbol_matches_soaddr(sym, soaddr)) {
return sym;
}
} while ((gnu_chain_[n++] & 1) == 0);
}
return nullptr;
}
ElfW(Sym)* soinfo::elf_addr_lookup(const void* addr) {
ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - load_bias;
// Search the library's symbol table for any defined symbol which
// contains this address.
for (size_t i = 0; i < nchain_; ++i) {
ElfW(Sym)* sym = symtab_ + i;
if (symbol_matches_soaddr(sym, soaddr)) {
return sym;
}
}
return nullptr;
}
static int open_library_in_zipfile(const char* const path,
off64_t* file_offset) {
TRACE("Trying zip file open from path '%s'", path);
// Treat an '!' character inside a path as the separator between the name
// of the zip file on disk and the subdirectory to search within it.
// For example, if path is "foo.zip!bar/bas/x.so", then we search for
// "bar/bas/x.so" within "foo.zip".
const char* separator = strchr(path, '!');
if (separator == nullptr) {
return -1;
}
char buf[512];
if (strlcpy(buf, path, sizeof(buf)) >= sizeof(buf)) {
PRINT("Warning: ignoring very long library path: %s", path);
return -1;
}
buf[separator - path] = '\0';
const char* zip_path = buf;
const char* file_path = &buf[separator - path + 1];
int fd = TEMP_FAILURE_RETRY(open(zip_path, O_RDONLY | O_CLOEXEC));
if (fd == -1) {
return -1;
}
ZipArchiveHandle handle;
if (OpenArchiveFd(fd, "", &handle, false) != 0) {
// invalid zip-file (?)
close(fd);
return -1;
}
auto archive_guard = make_scope_guard([&]() {
CloseArchive(handle);
});
ZipEntry entry;
if (FindEntry(handle, ZipEntryName(file_path), &entry) != 0) {
// Entry was not found.
close(fd);
return -1;
}
// Check if it is properly stored
if (entry.method != kCompressStored || (entry.offset % PAGE_SIZE) != 0) {
close(fd);
return -1;
}
*file_offset = entry.offset;
return fd;
}
static bool format_path(char* buf, size_t buf_size, const char* path, const char* name) {
int n = __libc_format_buffer(buf, buf_size, "%s/%s", path, name);
if (n < 0 || n >= static_cast<int>(buf_size)) {
PRINT("Warning: ignoring very long library path: %s/%s", path, name);
return false;
}
return true;
}
static int open_library_on_default_path(const char* name, off64_t* file_offset) {
for (size_t i = 0; kDefaultLdPaths[i] != nullptr; ++i) {
char buf[512];
if (!format_path(buf, sizeof(buf), kDefaultLdPaths[i], name)) {
continue;
}
int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
if (fd != -1) {
*file_offset = 0;
return fd;
}
}
return -1;
}
static int open_library_on_ld_library_path(const char* name, off64_t* file_offset) {
for (const auto& path_str : g_ld_library_paths) {
char buf[512];
const char* const path = path_str.c_str();
if (!format_path(buf, sizeof(buf), path, name)) {
continue;
}
int fd = -1;
if (strchr(buf, '!') != nullptr) {
fd = open_library_in_zipfile(buf, file_offset);
}
if (fd == -1) {
fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
if (fd != -1) {
*file_offset = 0;
}
}
if (fd != -1) {
return fd;
}
}
return -1;
}
static int open_library(const char* name, off64_t* file_offset) {
TRACE("[ opening %s ]", name);
// If the name contains a slash, we should attempt to open it directly and not search the paths.
if (strchr(name, '/') != nullptr) {
if (strchr(name, '!') != nullptr) {
int fd = open_library_in_zipfile(name, file_offset);
if (fd != -1) {
return fd;
}
}
int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
if (fd != -1) {
*file_offset = 0;
}
return fd;
}
// Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
int fd = open_library_on_ld_library_path(name, file_offset);
if (fd == -1) {
fd = open_library_on_default_path(name, file_offset);
}
return fd;
}
template<typename F>
static void for_each_dt_needed(const soinfo* si, F action) {
for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_NEEDED) {
action(si->get_string(d->d_un.d_val));
}
}
}
static soinfo* load_library(LoadTaskList& load_tasks,
const char* name, int rtld_flags,
const android_dlextinfo* extinfo) {
int fd = -1;
off64_t file_offset = 0;
ScopedFd file_guard(-1);
if (extinfo != nullptr && (extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) != 0) {
fd = extinfo->library_fd;
if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
file_offset = extinfo->library_fd_offset;
}
} else {
// Open the file.
fd = open_library(name, &file_offset);
if (fd == -1) {
DL_ERR("library \"%s\" not found", name);
return nullptr;
}
file_guard.reset(fd);
}
if ((file_offset % PAGE_SIZE) != 0) {
DL_ERR("file offset for the library \"%s\" is not page-aligned: %" PRId64, name, file_offset);
return nullptr;
}
if (file_offset < 0) {
DL_ERR("file offset for the library \"%s\" is negative: %" PRId64, name, file_offset);
return nullptr;
}
struct stat file_stat;
if (TEMP_FAILURE_RETRY(fstat(fd, &file_stat)) != 0) {
DL_ERR("unable to stat file for the library \"%s\": %s", name, strerror(errno));
return nullptr;
}
if (file_offset >= file_stat.st_size) {
DL_ERR("file offset for the library \"%s\" >= file size: %" PRId64 " >= %" PRId64,
name, file_offset, file_stat.st_size);
return nullptr;
}
// Check for symlink and other situations where
// file can have different names, unless ANDROID_DLEXT_FORCE_LOAD is set
if (extinfo == nullptr || (extinfo->flags & ANDROID_DLEXT_FORCE_LOAD) == 0) {
for (soinfo* si = solist; si != nullptr; si = si->next) {
if (si->get_st_dev() != 0 &&
si->get_st_ino() != 0 &&
si->get_st_dev() == file_stat.st_dev &&
si->get_st_ino() == file_stat.st_ino &&
si->get_file_offset() == file_offset) {
TRACE("library \"%s\" is already loaded under different name/path \"%s\" - "
"will return existing soinfo", name, si->get_realpath());
return si;
}
}
}
if ((rtld_flags & RTLD_NOLOAD) != 0) {
DL_ERR("library \"%s\" wasn't loaded and RTLD_NOLOAD prevented it", name);
return nullptr;
}
std::string realpath = name;
if (!realpath_fd(fd, &realpath)) {
PRINT("cannot resolve realpath for the library \"%s\": %s", name, strerror(errno));
realpath = name;
}
// Read the ELF header and load the segments.
ElfReader elf_reader(realpath.c_str(), fd, file_offset);
if (!elf_reader.Load(extinfo)) {
return nullptr;
}
soinfo* si = soinfo_alloc(realpath.c_str(), &file_stat, file_offset, rtld_flags);
if (si == nullptr) {
return nullptr;
}
si->base = elf_reader.load_start();
si->size = elf_reader.load_size();
si->load_bias = elf_reader.load_bias();
si->phnum = elf_reader.phdr_count();
si->phdr = elf_reader.loaded_phdr();
if (!si->prelink_image()) {
soinfo_free(si);
return nullptr;
}
for_each_dt_needed(si, [&] (const char* name) {
load_tasks.push_back(LoadTask::create(name, si));
});
return si;
}
static soinfo *find_loaded_library_by_soname(const char* name) {
// Ignore filename with path.
if (strchr(name, '/') != nullptr) {
return nullptr;
}
for (soinfo* si = solist; si != nullptr; si = si->next) {
const char* soname = si->get_soname();
if (soname != nullptr && (strcmp(name, soname) == 0)) {
return si;
}
}
return nullptr;
}
static soinfo* find_library_internal(LoadTaskList& load_tasks, const char* name,
int rtld_flags, const android_dlextinfo* extinfo) {
soinfo* si = find_loaded_library_by_soname(name);
// Library might still be loaded, the accurate detection
// of this fact is done by load_library.
if (si == nullptr) {
TRACE("[ '%s' has not been found by soname. Trying harder...]", name);
si = load_library(load_tasks, name, rtld_flags, extinfo);
}
return si;
}
static void soinfo_unload(soinfo* si);
// TODO: this is slightly unusual way to construct
// the global group for relocation. Not every RTLD_GLOBAL
// library is included in this group for backwards-compatibility
// reasons.
//
// This group consists of the main executable, LD_PRELOADs
// and libraries with the DF_1_GLOBAL flag set.
static soinfo::soinfo_list_t make_global_group() {
soinfo::soinfo_list_t global_group;
for (soinfo* si = somain; si != nullptr; si = si->next) {
if ((si->get_dt_flags_1() & DF_1_GLOBAL) != 0) {
global_group.push_back(si);
}
}
return global_group;
}
static bool find_libraries(soinfo* start_with, const char* const library_names[],
size_t library_names_count, soinfo* soinfos[], std::vector<soinfo*>* ld_preloads,
size_t ld_preloads_count, int rtld_flags, const android_dlextinfo* extinfo) {
// Step 0: prepare.
LoadTaskList load_tasks;
for (size_t i = 0; i < library_names_count; ++i) {
const char* name = library_names[i];
load_tasks.push_back(LoadTask::create(name, start_with));
}
// Construct global_group.
soinfo::soinfo_list_t global_group = make_global_group();
// If soinfos array is null allocate one on stack.
// The array is needed in case of failure; for example
// when library_names[] = {libone.so, libtwo.so} and libone.so
// is loaded correctly but libtwo.so failed for some reason.
// In this case libone.so should be unloaded on return.
// See also implementation of failure_guard below.
if (soinfos == nullptr) {
size_t soinfos_size = sizeof(soinfo*)*library_names_count;
soinfos = reinterpret_cast<soinfo**>(alloca(soinfos_size));
memset(soinfos, 0, soinfos_size);
}
// list of libraries to link - see step 2.
size_t soinfos_count = 0;
auto failure_guard = make_scope_guard([&]() {
// Housekeeping
load_tasks.for_each([] (LoadTask* t) {
LoadTask::deleter(t);
});
for (size_t i = 0; i<soinfos_count; ++i) {
soinfo_unload(soinfos[i]);
}
});
// Step 1: load and pre-link all DT_NEEDED libraries in breadth first order.
for (LoadTask::unique_ptr task(load_tasks.pop_front());
task.get() != nullptr; task.reset(load_tasks.pop_front())) {
soinfo* si = find_library_internal(load_tasks, task->get_name(), rtld_flags, extinfo);
if (si == nullptr) {
return false;
}
soinfo* needed_by = task->get_needed_by();
if (needed_by != nullptr) {
needed_by->add_child(si);
}
if (si->is_linked()) {
si->increment_ref_count();
}
// When ld_preloads is not null, the first
// ld_preloads_count libs are in fact ld_preloads.
if (ld_preloads != nullptr && soinfos_count < ld_preloads_count) {
// Add LD_PRELOADed libraries to the global group for future runs.
// There is no need to explicitly add them to the global group
// for this run because they are going to appear in the local
// group in the correct order.
si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
ld_preloads->push_back(si);
}
if (soinfos_count < library_names_count) {
soinfos[soinfos_count++] = si;
}
}
// Step 2: link libraries.
soinfo::soinfo_list_t local_group;
walk_dependencies_tree(
start_with == nullptr ? soinfos : &start_with,
start_with == nullptr ? soinfos_count : 1,
[&] (soinfo* si) {
local_group.push_back(si);
return true;
});
// We need to increment ref_count in case
// the root of the local group was not linked.
bool was_local_group_root_linked = local_group.front()->is_linked();
bool linked = local_group.visit([&](soinfo* si) {
if (!si->is_linked()) {
if (!si->link_image(global_group, local_group, extinfo)) {
return false;
}
si->set_linked();
}
return true;
});
if (linked) {
failure_guard.disable();
}
if (!was_local_group_root_linked) {
local_group.front()->increment_ref_count();
}
return linked;
}
static soinfo* find_library(const char* name, int rtld_flags, const android_dlextinfo* extinfo) {
soinfo* si;
if (name == nullptr) {
si = somain;
} else if (!find_libraries(nullptr, &name, 1, &si, nullptr, 0, rtld_flags, extinfo)) {
return nullptr;
}
return si;
}
static void soinfo_unload(soinfo* root) {
// Note that the library can be loaded but not linked;
// in which case there is no root but we still need
// to walk the tree and unload soinfos involved.
//
// This happens on unsuccessful dlopen, when one of
// the DT_NEEDED libraries could not be linked/found.
if (root->is_linked()) {
root = root->get_local_group_root();
}
if (!root->can_unload()) {
TRACE("not unloading '%s' - the binary is flagged with NODELETE", root->get_soname());
return;
}
size_t ref_count = root->is_linked() ? root->decrement_ref_count() : 0;
if (ref_count == 0) {
soinfo::soinfo_list_t local_unload_list;
soinfo::soinfo_list_t external_unload_list;
soinfo::soinfo_list_t depth_first_list;
depth_first_list.push_back(root);
soinfo* si = nullptr;
while ((si = depth_first_list.pop_front()) != nullptr) {
if (local_unload_list.contains(si)) {
continue;
}
local_unload_list.push_back(si);
if (si->has_min_version(0)) {
soinfo* child = nullptr;
while ((child = si->get_children().pop_front()) != nullptr) {
TRACE("%s@%p needs to unload %s@%p", si->get_soname(), si, child->get_soname(), child);
if (local_unload_list.contains(child)) {
continue;
} else if (child->is_linked() && child->get_local_group_root() != root) {
external_unload_list.push_back(child);
} else {
depth_first_list.push_front(child);
}
}
} else {
#if !defined(__arm__)
__libc_fatal("soinfo for \"%s\"@%p has no version", si->get_soname(), si);
#else
PRINT("warning: soinfo for \"%s\"@%p has no version", si->get_soname(), si);
for_each_dt_needed(si, [&] (const char* library_name) {
TRACE("deprecated (old format of soinfo): %s needs to unload %s",
si->get_soname(), library_name);
soinfo* needed = find_library(library_name, RTLD_NOLOAD, nullptr);
if (needed != nullptr) {
// Not found: for example if symlink was deleted between dlopen and dlclose
// Since we cannot really handle errors at this point - print and continue.
PRINT("warning: couldn't find %s needed by %s on unload.",
library_name, si->get_soname());
return;
} else if (local_unload_list.contains(needed)) {
// already visited
return;
} else if (needed->is_linked() && needed->get_local_group_root() != root) {
// external group
external_unload_list.push_back(needed);
} else {
// local group
depth_first_list.push_front(needed);
}
});
#endif
}
}
local_unload_list.for_each([](soinfo* si) {
si->call_destructors();
});
while ((si = local_unload_list.pop_front()) != nullptr) {
notify_gdb_of_unload(si);
soinfo_free(si);
}
while ((si = external_unload_list.pop_front()) != nullptr) {
soinfo_unload(si);
}
} else {
TRACE("not unloading '%s' group, decrementing ref_count to %zd", root->get_soname(), ref_count);
}
}
void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
// Use basic string manipulation calls to avoid snprintf.
// snprintf indirectly calls pthread_getspecific to get the size of a buffer.
// When debug malloc is enabled, this call returns 0. This in turn causes
// snprintf to do nothing, which causes libraries to fail to load.
// See b/17302493 for further details.
// Once the above bug is fixed, this code can be modified to use
// snprintf again.
size_t required_len = strlen(kDefaultLdPaths[0]) + strlen(kDefaultLdPaths[1]) + 2;
if (buffer_size < required_len) {
__libc_fatal("android_get_LD_LIBRARY_PATH failed, buffer too small: "
"buffer len %zu, required len %zu", buffer_size, required_len);
}
char* end = stpcpy(buffer, kDefaultLdPaths[0]);
*end = ':';
strcpy(end + 1, kDefaultLdPaths[1]);
}
void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
parse_LD_LIBRARY_PATH(ld_library_path);
}
soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo) {
if ((flags & ~(RTLD_NOW|RTLD_LAZY|RTLD_LOCAL|RTLD_GLOBAL|RTLD_NODELETE|RTLD_NOLOAD)) != 0) {
DL_ERR("invalid flags to dlopen: %x", flags);
return nullptr;
}
if (extinfo != nullptr) {
if ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0) {
DL_ERR("invalid extended flags to android_dlopen_ext: 0x%" PRIx64, extinfo->flags);
return nullptr;
}
if ((extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD) == 0 &&
(extinfo->flags & ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET) != 0) {
DL_ERR("invalid extended flag combination (ANDROID_DLEXT_USE_LIBRARY_FD_OFFSET without "
"ANDROID_DLEXT_USE_LIBRARY_FD): 0x%" PRIx64, extinfo->flags);
return nullptr;
}
}
ProtectedDataGuard guard;
soinfo* si = find_library(name, flags, extinfo);
if (si != nullptr) {
si->call_constructors();
}
return si;
}
void do_dlclose(soinfo* si) {
ProtectedDataGuard guard;
soinfo_unload(si);
}
static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
typedef ElfW(Addr) (*ifunc_resolver_t)(void);
ifunc_resolver_t ifunc_resolver = reinterpret_cast<ifunc_resolver_t>(resolver_addr);
ElfW(Addr) ifunc_addr = ifunc_resolver();
TRACE_TYPE(RELO, "Called ifunc_resolver@%p. The result is %p",
ifunc_resolver, reinterpret_cast<void*>(ifunc_addr));
return ifunc_addr;
}
const version_info* VersionTracker::get_version_info(ElfW(Versym) source_symver) const {
if (source_symver < 2 ||
source_symver >= version_infos.size() ||
version_infos[source_symver].name == nullptr) {
return nullptr;
}
return &version_infos[source_symver];
}
void VersionTracker::add_version_info(size_t source_index,
ElfW(Word) elf_hash,
const char* ver_name,
const soinfo* target_si) {
if (source_index >= version_infos.size()) {
version_infos.resize(source_index+1);
}
version_infos[source_index].elf_hash = elf_hash;
version_infos[source_index].name = ver_name;
version_infos[source_index].target_si = target_si;
}
bool VersionTracker::init_verneed(const soinfo* si_from) {
uintptr_t verneed_ptr = si_from->get_verneed_ptr();
if (verneed_ptr == 0) {
return true;
}
size_t verneed_cnt = si_from->get_verneed_cnt();
for (size_t i = 0, offset = 0; i<verneed_cnt; ++i) {
const ElfW(Verneed)* verneed = reinterpret_cast<ElfW(Verneed)*>(verneed_ptr + offset);
size_t vernaux_offset = offset + verneed->vn_aux;
offset += verneed->vn_next;
if (verneed->vn_version != 1) {
DL_ERR("unsupported verneed[%zd] vn_version: %d (expected 1)", i, verneed->vn_version);
return false;
}
const char* target_soname = si_from->get_string(verneed->vn_file);
// find it in dependencies
soinfo* target_si = si_from->get_children().find_if([&](const soinfo* si) {
return strcmp(si->get_soname(), target_soname) == 0;
});
if (target_si == nullptr) {
DL_ERR("cannot find \"%s\" from verneed[%zd] in DT_NEEDED list for \"%s\"",
target_soname, i, si_from->get_soname());
return false;
}
for (size_t j = 0; j<verneed->vn_cnt; ++j) {
const ElfW(Vernaux)* vernaux = reinterpret_cast<ElfW(Vernaux)*>(verneed_ptr + vernaux_offset);
vernaux_offset += vernaux->vna_next;
const ElfW(Word) elf_hash = vernaux->vna_hash;
const char* ver_name = si_from->get_string(vernaux->vna_name);
ElfW(Half) source_index = vernaux->vna_other;
add_version_info(source_index, elf_hash, ver_name, target_si);
}
}
return true;
}
bool VersionTracker::init_verdef(const soinfo* si_from) {
return for_each_verdef(si_from,
[&](size_t, const ElfW(Verdef)* verdef, const ElfW(Verdaux)* verdaux) {
add_version_info(verdef->vd_ndx, verdef->vd_hash,
si_from->get_string(verdaux->vda_name), si_from);
return false;
}
);
}
bool VersionTracker::init(const soinfo* si_from) {
if (!si_from->has_min_version(2)) {
return true;
}
return init_verneed(si_from) && init_verdef(si_from);
}
#if !defined(__mips__)
#if defined(USE_RELA)
static ElfW(Addr) get_addend(ElfW(Rela)* rela, ElfW(Addr) reloc_addr __unused) {
return rela->r_addend;
}
#else
static ElfW(Addr) get_addend(ElfW(Rel)* rel, ElfW(Addr) reloc_addr) {
if (ELFW(R_TYPE)(rel->r_info) == R_GENERIC_RELATIVE ||
ELFW(R_TYPE)(rel->r_info) == R_GENERIC_IRELATIVE) {
return *reinterpret_cast<ElfW(Addr)*>(reloc_addr);
}
return 0;
}
#endif
template<typename ElfRelIteratorT>
bool soinfo::relocate(ElfRelIteratorT&& rel_iterator, const soinfo_list_t& global_group,
const soinfo_list_t& local_group) {
VersionTracker version_tracker;
if (!version_tracker.init(this)) {
return false;
}
for (size_t idx = 0; rel_iterator.has_next(); ++idx) {
const auto rel = rel_iterator.next();
if (rel == nullptr) {
return false;
}
ElfW(Word) type = ELFW(R_TYPE)(rel->r_info);
ElfW(Word) sym = ELFW(R_SYM)(rel->r_info);
ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + load_bias);
ElfW(Addr) sym_addr = 0;
const char* sym_name = nullptr;
ElfW(Addr) addend = get_addend(rel, reloc);
DEBUG("Processing '%s' relocation at index %zd", get_soname(), idx);
if (type == R_GENERIC_NONE) {
continue;
}
const ElfW(Sym)* s = nullptr;
soinfo* lsi = nullptr;
if (sym != 0) {
sym_name = get_string(symtab_[sym].st_name);
const ElfW(Versym)* sym_ver_ptr = get_versym(sym);
ElfW(Versym) sym_ver = sym_ver_ptr == nullptr ? 0 : *sym_ver_ptr;
if (sym_ver == VER_NDX_LOCAL || sym_ver == VER_NDX_GLOBAL) {
// there is no version info for this one
if (!soinfo_do_lookup(this, sym_name, nullptr, &lsi, global_group, local_group, &s)) {
return false;
}
} else {
const version_info* vi = version_tracker.get_version_info(sym_ver);
if (vi == nullptr) {
DL_ERR("cannot find verneed/verdef for version index=%d "
"referenced by symbol \"%s\" at \"%s\"", sym_ver, sym_name, get_soname());
return false;
}
if (!soinfo_do_lookup(this, sym_name, vi, &lsi, global_group, local_group, &s)) {
return false;
}
}
if (s == nullptr) {
// We only allow an undefined symbol if this is a weak reference...
s = &symtab_[sym];
if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, get_soname());
return false;
}
/* IHI0044C AAELF 4.5.1.1:
Libraries are not searched to resolve weak references.
It is not an error for a weak reference to remain unsatisfied.
During linking, the value of an undefined weak reference is:
- Zero if the relocation type is absolute
- The address of the place if the relocation is pc-relative
- The address of nominal base address if the relocation
type is base-relative.
*/
switch (type) {
case R_GENERIC_JUMP_SLOT:
case R_GENERIC_GLOB_DAT:
case R_GENERIC_RELATIVE:
case R_GENERIC_IRELATIVE:
#if defined(__aarch64__)
case R_AARCH64_ABS64:
case R_AARCH64_ABS32:
case R_AARCH64_ABS16:
#elif defined(__x86_64__)
case R_X86_64_32:
case R_X86_64_64:
#elif defined(__arm__)
case R_ARM_ABS32:
#elif defined(__i386__)
case R_386_32:
#endif
/*
* The sym_addr was initialized to be zero above, or the relocation
* code below does not care about value of sym_addr.
* No need to do anything.
*/
break;
#if defined(__x86_64__)
case R_X86_64_PC32:
sym_addr = reloc;
break;
#elif defined(__i386__)
case R_386_PC32:
sym_addr = reloc;
break;
#endif
default:
DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
return false;
}
} else {
// We got a definition.
sym_addr = lsi->resolve_symbol_address(s);
}
count_relocation(kRelocSymbol);
}
switch (type) {
case R_GENERIC_JUMP_SLOT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %16p <- %16p %s\n",
reinterpret_cast<void*>(reloc),
reinterpret_cast<void*>(sym_addr + addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + addend);
break;
case R_GENERIC_GLOB_DAT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO GLOB_DAT %16p <- %16p %s\n",
reinterpret_cast<void*>(reloc),
reinterpret_cast<void*>(sym_addr + addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + addend);
break;
case R_GENERIC_RELATIVE:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO RELATIVE %16p <- %16p\n",
reinterpret_cast<void*>(reloc),
reinterpret_cast<void*>(load_bias + addend));
*reinterpret_cast<ElfW(Addr)*>(reloc) = (load_bias + addend);
break;
case R_GENERIC_IRELATIVE:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO IRELATIVE %16p <- %16p\n",
reinterpret_cast<void*>(reloc),
reinterpret_cast<void*>(load_bias + addend));
*reinterpret_cast<ElfW(Addr)*>(reloc) = call_ifunc_resolver(load_bias + addend);
break;
#if defined(__aarch64__)
case R_AARCH64_ABS64:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
reloc, (sym_addr + addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + addend);
break;
case R_AARCH64_ABS32:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
reloc, (sym_addr + addend), sym_name);
{
const ElfW(Addr) reloc_value = *reinterpret_cast<ElfW(Addr)*>(reloc);
const ElfW(Addr) min_value = static_cast<ElfW(Addr)>(INT32_MIN);
const ElfW(Addr) max_value = static_cast<ElfW(Addr)>(UINT32_MAX);
if ((min_value <= (reloc_value + (sym_addr + addend))) &&
((reloc_value + (sym_addr + addend)) <= max_value)) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + addend);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
(reloc_value + (sym_addr + addend)), min_value, max_value);
return false;
}
}
break;
case R_AARCH64_ABS16:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
reloc, (sym_addr + addend), sym_name);
{
const ElfW(Addr) reloc_value = *reinterpret_cast<ElfW(Addr)*>(reloc);
const ElfW(Addr) min_value = static_cast<ElfW(Addr)>(INT16_MIN);
const ElfW(Addr) max_value = static_cast<ElfW(Addr)>(UINT16_MAX);
if ((min_value <= (reloc_value + (sym_addr + addend))) &&
((reloc_value + (sym_addr + addend)) <= max_value)) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + addend);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
reloc_value + (sym_addr + addend), min_value, max_value);
return false;
}
}
break;
case R_AARCH64_PREL64:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + addend), rel->r_offset, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + addend) - rel->r_offset;
break;
case R_AARCH64_PREL32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + addend), rel->r_offset, sym_name);
{
const ElfW(Addr) reloc_value = *reinterpret_cast<ElfW(Addr)*>(reloc);
const ElfW(Addr) min_value = static_cast<ElfW(Addr)>(INT32_MIN);
const ElfW(Addr) max_value = static_cast<ElfW(Addr)>(UINT32_MAX);
if ((min_value <= (reloc_value + ((sym_addr + addend) - rel->r_offset))) &&
((reloc_value + ((sym_addr + addend) - rel->r_offset)) <= max_value)) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + addend) - rel->r_offset);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
reloc_value + ((sym_addr + addend) - rel->r_offset), min_value, max_value);
return false;
}
}
break;
case R_AARCH64_PREL16:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + addend), rel->r_offset, sym_name);
{
const ElfW(Addr) reloc_value = *reinterpret_cast<ElfW(Addr)*>(reloc);
const ElfW(Addr) min_value = static_cast<ElfW(Addr)>(INT16_MIN);
const ElfW(Addr) max_value = static_cast<ElfW(Addr)>(UINT16_MAX);
if ((min_value <= (reloc_value + ((sym_addr + addend) - rel->r_offset))) &&
((reloc_value + ((sym_addr + addend) - rel->r_offset)) <= max_value)) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + addend) - rel->r_offset);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
reloc_value + ((sym_addr + addend) - rel->r_offset), min_value, max_value);
return false;
}
}
break;
case R_AARCH64_COPY:
/*
* ET_EXEC is not supported so this should not happen.
*
* http://infocenter.arm.com/help/topic/com.arm.doc.ihi0056b/IHI0056B_aaelf64.pdf
*
* Section 4.6.11 "Dynamic relocations"
* R_AARCH64_COPY may only appear in executable objects where e_type is
* set to ET_EXEC.
*/
DL_ERR("%s R_AARCH64_COPY relocations are not supported", get_soname());
return false;
case R_AARCH64_TLS_TPREL64:
TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
reloc, (sym_addr + addend), rel->r_offset);
break;
case R_AARCH64_TLS_DTPREL32:
TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
reloc, (sym_addr + addend), rel->r_offset);
break;
#elif defined(__x86_64__)
case R_X86_64_32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO R_X86_64_32 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + addend;
break;
case R_X86_64_64:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO R_X86_64_64 %08zx <- +%08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + addend;
break;
case R_X86_64_PC32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO R_X86_64_PC32 %08zx <- +%08zx (%08zx - %08zx) %s",
static_cast<size_t>(reloc), static_cast<size_t>(sym_addr - reloc),
static_cast<size_t>(sym_addr), static_cast<size_t>(reloc), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + addend - reloc;
break;
#elif defined(__arm__)
case R_ARM_ABS32:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO ABS %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
break;
case R_ARM_REL32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO REL32 %08x <- %08x - %08x %s",
reloc, sym_addr, rel->r_offset, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr - rel->r_offset;
break;
case R_ARM_COPY:
/*
* ET_EXEC is not supported so this should not happen.
*
* http://infocenter.arm.com/help/topic/com.arm.doc.ihi0044d/IHI0044D_aaelf.pdf
*
* Section 4.6.1.10 "Dynamic relocations"
* R_ARM_COPY may only appear in executable objects where e_type is
* set to ET_EXEC.
*/
DL_ERR("%s R_ARM_COPY relocations are not supported", get_soname());
return false;
#elif defined(__i386__)
case R_386_32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO R_386_32 %08x <- +%08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
break;
case R_386_PC32:
count_relocation(kRelocRelative);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO R_386_PC32 %08x <- +%08x (%08x - %08x) %s",
reloc, (sym_addr - reloc), sym_addr, reloc, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr - reloc);
break;
#endif
default:
DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
return false;
}
}
return true;
}
#endif // !defined(__mips__)
void soinfo::call_array(const char* array_name __unused, linker_function_t* functions,
size_t count, bool reverse) {
if (functions == nullptr) {
return;
}
TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, get_soname());
int begin = reverse ? (count - 1) : 0;
int end = reverse ? -1 : count;
int step = reverse ? -1 : 1;
for (int i = begin; i != end; i += step) {
TRACE("[ %s[%d] == %p ]", array_name, i, functions[i]);
call_function("function", functions[i]);
}
TRACE("[ Done calling %s for '%s' ]", array_name, get_soname());
}
void soinfo::call_function(const char* function_name __unused, linker_function_t function) {
if (function == nullptr || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
return;
}
TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, get_soname());
function();
TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, get_soname());
}
void soinfo::call_pre_init_constructors() {
// DT_PREINIT_ARRAY functions are called before any other constructors for executables,
// but ignored in a shared library.
call_array("DT_PREINIT_ARRAY", preinit_array_, preinit_array_count_, false);
}
void soinfo::call_constructors() {
if (constructors_called) {
return;
}
// We set constructors_called before actually calling the constructors, otherwise it doesn't
// protect against recursive constructor calls. One simple example of constructor recursion
// is the libc debug malloc, which is implemented in libc_malloc_debug_leak.so:
// 1. The program depends on libc, so libc's constructor is called here.
// 2. The libc constructor calls dlopen() to load libc_malloc_debug_leak.so.
// 3. dlopen() calls the constructors on the newly created
// soinfo for libc_malloc_debug_leak.so.
// 4. The debug .so depends on libc, so CallConstructors is
// called again with the libc soinfo. If it doesn't trigger the early-
// out above, the libc constructor will be called again (recursively!).
constructors_called = true;
if (!is_main_executable() && preinit_array_ != nullptr) {
// The GNU dynamic linker silently ignores these, but we warn the developer.
PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
get_soname(), preinit_array_count_);
}
get_children().for_each([] (soinfo* si) {
si->call_constructors();
});
TRACE("\"%s\": calling constructors", get_soname());
// DT_INIT should be called before DT_INIT_ARRAY if both are present.
call_function("DT_INIT", init_func_);
call_array("DT_INIT_ARRAY", init_array_, init_array_count_, false);
}
void soinfo::call_destructors() {
if (!constructors_called) {
return;
}
TRACE("\"%s\": calling destructors", get_soname());
// DT_FINI_ARRAY must be parsed in reverse order.
call_array("DT_FINI_ARRAY", fini_array_, fini_array_count_, true);
// DT_FINI should be called after DT_FINI_ARRAY if both are present.
call_function("DT_FINI", fini_func_);
// This is needed on second call to dlopen
// after library has been unloaded with RTLD_NODELETE
constructors_called = false;
}
void soinfo::add_child(soinfo* child) {
if (has_min_version(0)) {
child->parents_.push_back(this);
this->children_.push_back(child);
}
}
void soinfo::remove_all_links() {
if (!has_min_version(0)) {
return;
}
// 1. Untie connected soinfos from 'this'.
children_.for_each([&] (soinfo* child) {
child->parents_.remove_if([&] (const soinfo* parent) {
return parent == this;
});
});
parents_.for_each([&] (soinfo* parent) {
parent->children_.remove_if([&] (const soinfo* child) {
return child == this;
});
});
// 2. Once everything untied - clear local lists.
parents_.clear();
children_.clear();
}
dev_t soinfo::get_st_dev() const {
if (has_min_version(0)) {
return st_dev_;
}
return 0;
};
ino_t soinfo::get_st_ino() const {
if (has_min_version(0)) {
return st_ino_;
}
return 0;
}
off64_t soinfo::get_file_offset() const {
if (has_min_version(1)) {
return file_offset_;
}
return 0;
}
uint32_t soinfo::get_rtld_flags() const {
if (has_min_version(1)) {
return rtld_flags_;
}
return 0;
}
uint32_t soinfo::get_dt_flags_1() const {
if (has_min_version(1)) {
return dt_flags_1_;
}
return 0;
}
void soinfo::set_dt_flags_1(uint32_t dt_flags_1) {
if (has_min_version(1)) {
if ((dt_flags_1 & DF_1_GLOBAL) != 0) {
rtld_flags_ |= RTLD_GLOBAL;
}
if ((dt_flags_1 & DF_1_NODELETE) != 0) {
rtld_flags_ |= RTLD_NODELETE;
}
dt_flags_1_ = dt_flags_1;
}
}
const char* soinfo::get_realpath() const {
#if defined(__arm__)
if (has_min_version(2)) {
return realpath_.c_str();
} else {
return old_name_;
}
#else
return realpath_.c_str();
#endif
}
const char* soinfo::get_soname() const {
#if defined(__arm__)
if (has_min_version(2)) {
return soname_;
} else {
return old_name_;
}
#else
return soname_;
#endif
}
// This is a return on get_children()/get_parents() if
// 'this->flags' does not have FLAG_NEW_SOINFO set.
static soinfo::soinfo_list_t g_empty_list;
soinfo::soinfo_list_t& soinfo::get_children() {
if (has_min_version(0)) {
return children_;
}
return g_empty_list;
}
const soinfo::soinfo_list_t& soinfo::get_children() const {
if (has_min_version(0)) {
return children_;
}
return g_empty_list;
}
soinfo::soinfo_list_t& soinfo::get_parents() {
if (has_min_version(0)) {
return parents_;
}
return g_empty_list;
}
ElfW(Addr) soinfo::resolve_symbol_address(const ElfW(Sym)* s) const {
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
return call_ifunc_resolver(s->st_value + load_bias);
}
return static_cast<ElfW(Addr)>(s->st_value + load_bias);
}
const char* soinfo::get_string(ElfW(Word) index) const {
if (has_min_version(1) && (index >= strtab_size_)) {
__libc_fatal("%s: strtab out of bounds error; STRSZ=%zd, name=%d",
get_soname(), strtab_size_, index);
}
return strtab_ + index;
}
bool soinfo::is_gnu_hash() const {
return (flags_ & FLAG_GNU_HASH) != 0;
}
bool soinfo::can_unload() const {
return (get_rtld_flags() & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
}
bool soinfo::is_linked() const {
return (flags_ & FLAG_LINKED) != 0;
}
bool soinfo::is_main_executable() const {
return (flags_ & FLAG_EXE) != 0;
}
void soinfo::set_linked() {
flags_ |= FLAG_LINKED;
}
void soinfo::set_linker_flag() {
flags_ |= FLAG_LINKER;
}
void soinfo::set_main_executable() {
flags_ |= FLAG_EXE;
}
void soinfo::increment_ref_count() {
local_group_root_->ref_count_++;
}
size_t soinfo::decrement_ref_count() {
return --local_group_root_->ref_count_;
}
soinfo* soinfo::get_local_group_root() const {
return local_group_root_;
}
/* Force any of the closed stdin, stdout and stderr to be associated with
/dev/null. */
static int nullify_closed_stdio() {
int dev_null, i, status;
int return_value = 0;
dev_null = TEMP_FAILURE_RETRY(open("/dev/null", O_RDWR));
if (dev_null < 0) {
DL_ERR("cannot open /dev/null: %s", strerror(errno));
return -1;
}
TRACE("[ Opened /dev/null file-descriptor=%d]", dev_null);
/* If any of the stdio file descriptors is valid and not associated
with /dev/null, dup /dev/null to it. */
for (i = 0; i < 3; i++) {
/* If it is /dev/null already, we are done. */
if (i == dev_null) {
continue;
}
TRACE("[ Nullifying stdio file descriptor %d]", i);
status = TEMP_FAILURE_RETRY(fcntl(i, F_GETFL));
/* If file is opened, we are good. */
if (status != -1) {
continue;
}
/* The only error we allow is that the file descriptor does not
exist, in which case we dup /dev/null to it. */
if (errno != EBADF) {
DL_ERR("fcntl failed: %s", strerror(errno));
return_value = -1;
continue;
}
/* Try dupping /dev/null to this stdio file descriptor and
repeat if there is a signal. Note that any errors in closing
the stdio descriptor are lost. */
status = TEMP_FAILURE_RETRY(dup2(dev_null, i));
if (status < 0) {
DL_ERR("dup2 failed: %s", strerror(errno));
return_value = -1;
continue;
}
}
/* If /dev/null is not one of the stdio file descriptors, close it. */
if (dev_null > 2) {
TRACE("[ Closing /dev/null file-descriptor=%d]", dev_null);
status = TEMP_FAILURE_RETRY(close(dev_null));
if (status == -1) {
DL_ERR("close failed: %s", strerror(errno));
return_value = -1;
}
}
return return_value;
}
bool soinfo::prelink_image() {
/* Extract dynamic section */
ElfW(Word) dynamic_flags = 0;
phdr_table_get_dynamic_section(phdr, phnum, load_bias, &dynamic, &dynamic_flags);
/* We can't log anything until the linker is relocated */
bool relocating_linker = (flags_ & FLAG_LINKER) != 0;
if (!relocating_linker) {
INFO("[ linking %s ]", get_soname());
DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(base), flags_);
}
if (dynamic == nullptr) {
if (!relocating_linker) {
DL_ERR("missing PT_DYNAMIC in \"%s\"", get_soname());
}
return false;
} else {
if (!relocating_linker) {
DEBUG("dynamic = %p", dynamic);
}
}
#if defined(__arm__)
(void) phdr_table_get_arm_exidx(phdr, phnum, load_bias,
&ARM_exidx, &ARM_exidx_count);
#endif
// Extract useful information from dynamic section.
// Note that: "Except for the DT_NULL element at the end of the array,
// and the relative order of DT_NEEDED elements, entries may appear in any order."
//
// source: http://www.sco.com/developers/gabi/1998-04-29/ch5.dynamic.html
uint32_t needed_count = 0;
for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
DEBUG("d = %p, d[0](tag) = %p d[1](val) = %p",
d, reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
switch (d->d_tag) {
case DT_SONAME:
// this is parsed after we have strtab initialized (see below).
break;
case DT_HASH:
nbucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
nchain_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
bucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8);
chain_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr + 8 + nbucket_ * 4);
break;
case DT_GNU_HASH:
gnu_nbucket_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[0];
// skip symndx
gnu_maskwords_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[2];
gnu_shift2_ = reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[3];
gnu_bloom_filter_ = reinterpret_cast<ElfW(Addr)*>(load_bias + d->d_un.d_ptr + 16);
gnu_bucket_ = reinterpret_cast<uint32_t*>(gnu_bloom_filter_ + gnu_maskwords_);
// amend chain for symndx = header[1]
gnu_chain_ = gnu_bucket_ + gnu_nbucket_ -
reinterpret_cast<uint32_t*>(load_bias + d->d_un.d_ptr)[1];
if (!powerof2(gnu_maskwords_)) {
DL_ERR("invalid maskwords for gnu_hash = 0x%x, in \"%s\" expecting power to two",
gnu_maskwords_, get_realpath());
return false;
}
--gnu_maskwords_;
flags_ |= FLAG_GNU_HASH;
break;
case DT_STRTAB:
strtab_ = reinterpret_cast<const char*>(load_bias + d->d_un.d_ptr);
break;
case DT_STRSZ:
strtab_size_ = d->d_un.d_val;
break;
case DT_SYMTAB:
symtab_ = reinterpret_cast<ElfW(Sym)*>(load_bias + d->d_un.d_ptr);
break;
case DT_SYMENT:
if (d->d_un.d_val != sizeof(ElfW(Sym))) {
DL_ERR("invalid DT_SYMENT: %zd in \"%s\"",
static_cast<size_t>(d->d_un.d_val), get_realpath());
return false;
}
break;
case DT_PLTREL:
#if defined(USE_RELA)
if (d->d_un.d_val != DT_RELA) {
DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_RELA", get_realpath());
return false;
}
#else
if (d->d_un.d_val != DT_REL) {
DL_ERR("unsupported DT_PLTREL in \"%s\"; expected DT_REL", get_realpath());
return false;
}
#endif
break;
case DT_JMPREL:
#if defined(USE_RELA)
plt_rela_ = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
#else
plt_rel_ = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
#endif
break;
case DT_PLTRELSZ:
#if defined(USE_RELA)
plt_rela_count_ = d->d_un.d_val / sizeof(ElfW(Rela));
#else
plt_rel_count_ = d->d_un.d_val / sizeof(ElfW(Rel));
#endif
break;
case DT_PLTGOT:
#if defined(__mips__)
// Used by mips and mips64.
plt_got_ = reinterpret_cast<ElfW(Addr)**>(load_bias + d->d_un.d_ptr);
#endif
// Ignore for other platforms... (because RTLD_LAZY is not supported)
break;
case DT_DEBUG:
// Set the DT_DEBUG entry to the address of _r_debug for GDB
// if the dynamic table is writable
// FIXME: not working currently for N64
// The flags for the LOAD and DYNAMIC program headers do not agree.
// The LOAD section containing the dynamic table has been mapped as
// read-only, but the DYNAMIC header claims it is writable.
#if !(defined(__mips__) && defined(__LP64__))
if ((dynamic_flags & PF_W) != 0) {
d->d_un.d_val = reinterpret_cast<uintptr_t>(&_r_debug);
}
#endif
break;
#if defined(USE_RELA)
case DT_RELA:
rela_ = reinterpret_cast<ElfW(Rela)*>(load_bias + d->d_un.d_ptr);
break;
case DT_RELASZ:
rela_count_ = d->d_un.d_val / sizeof(ElfW(Rela));
break;
case DT_ANDROID_RELA:
android_relocs_ = reinterpret_cast<uint8_t*>(load_bias + d->d_un.d_ptr);
break;
case DT_ANDROID_RELASZ:
android_relocs_size_ = d->d_un.d_val;
break;
case DT_ANDROID_REL:
DL_ERR("unsupported DT_ANDROID_REL in \"%s\"", get_realpath());
return false;
case DT_ANDROID_RELSZ:
DL_ERR("unsupported DT_ANDROID_RELSZ in \"%s\"", get_realpath());
return false;
case DT_RELAENT:
if (d->d_un.d_val != sizeof(ElfW(Rela))) {
DL_ERR("invalid DT_RELAENT: %zd", static_cast<size_t>(d->d_un.d_val));
return false;
}
break;
// ignored (see DT_RELCOUNT comments for details)
case DT_RELACOUNT:
break;
case DT_REL:
DL_ERR("unsupported DT_REL in \"%s\"", get_realpath());
return false;
case DT_RELSZ:
DL_ERR("unsupported DT_RELSZ in \"%s\"", get_realpath());
return false;
#else
case DT_REL:
rel_ = reinterpret_cast<ElfW(Rel)*>(load_bias + d->d_un.d_ptr);
break;
case DT_RELSZ:
rel_count_ = d->d_un.d_val / sizeof(ElfW(Rel));
break;
case DT_RELENT:
if (d->d_un.d_val != sizeof(ElfW(Rel))) {
DL_ERR("invalid DT_RELENT: %zd", static_cast<size_t>(d->d_un.d_val));
return false;
}
break;
case DT_ANDROID_REL:
android_relocs_ = reinterpret_cast<uint8_t*>(load_bias + d->d_un.d_ptr);
break;
case DT_ANDROID_RELSZ:
android_relocs_size_ = d->d_un.d_val;
break;
case DT_ANDROID_RELA:
DL_ERR("unsupported DT_ANDROID_RELA in \"%s\"", get_realpath());
return false;
case DT_ANDROID_RELASZ:
DL_ERR("unsupported DT_ANDROID_RELASZ in \"%s\"", get_realpath());
return false;
// "Indicates that all RELATIVE relocations have been concatenated together,
// and specifies the RELATIVE relocation count."
//
// TODO: Spec also mentions that this can be used to optimize relocation process;
// Not currently used by bionic linker - ignored.
case DT_RELCOUNT:
break;
case DT_RELA:
DL_ERR("unsupported DT_RELA in \"%s\"", get_realpath());
return false;
case DT_RELASZ:
DL_ERR("unsupported DT_RELASZ in \"%s\"", get_realpath());
return false;
#endif
case DT_INIT:
init_func_ = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
DEBUG("%s constructors (DT_INIT) found at %p", get_realpath(), init_func_);
break;
case DT_FINI:
fini_func_ = reinterpret_cast<linker_function_t>(load_bias + d->d_un.d_ptr);
DEBUG("%s destructors (DT_FINI) found at %p", get_realpath(), fini_func_);
break;
case DT_INIT_ARRAY:
init_array_ = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", get_realpath(), init_array_);
break;
case DT_INIT_ARRAYSZ:
init_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
break;
case DT_FINI_ARRAY:
fini_array_ = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", get_realpath(), fini_array_);
break;
case DT_FINI_ARRAYSZ:
fini_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
break;
case DT_PREINIT_ARRAY:
preinit_array_ = reinterpret_cast<linker_function_t*>(load_bias + d->d_un.d_ptr);
DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", get_realpath(), preinit_array_);
break;
case DT_PREINIT_ARRAYSZ:
preinit_array_count_ = static_cast<uint32_t>(d->d_un.d_val) / sizeof(ElfW(Addr));
break;
case DT_TEXTREL:
#if defined(__LP64__)
DL_ERR("text relocations (DT_TEXTREL) found in 64-bit ELF file \"%s\"", get_realpath());
return false;
#else
has_text_relocations = true;
break;
#endif
case DT_SYMBOLIC:
has_DT_SYMBOLIC = true;
break;
case DT_NEEDED:
++needed_count;
break;
case DT_FLAGS:
if (d->d_un.d_val & DF_TEXTREL) {
#if defined(__LP64__)
DL_ERR("text relocations (DF_TEXTREL) found in 64-bit ELF file \"%s\"", get_realpath());
return false;
#else
has_text_relocations = true;
#endif
}
if (d->d_un.d_val & DF_SYMBOLIC) {
has_DT_SYMBOLIC = true;
}
break;
case DT_FLAGS_1:
set_dt_flags_1(d->d_un.d_val);
if ((d->d_un.d_val & ~SUPPORTED_DT_FLAGS_1) != 0) {
DL_WARN("Unsupported flags DT_FLAGS_1=%p", reinterpret_cast<void*>(d->d_un.d_val));
}
break;
#if defined(__mips__)
case DT_MIPS_RLD_MAP:
// Set the DT_MIPS_RLD_MAP entry to the address of _r_debug for GDB.
{
r_debug** dp = reinterpret_cast<r_debug**>(load_bias + d->d_un.d_ptr);
*dp = &_r_debug;
}
break;
case DT_MIPS_RLD_MAP2:
// Set the DT_MIPS_RLD_MAP2 entry to the address of _r_debug for GDB.
{
r_debug** dp = reinterpret_cast<r_debug**>(
reinterpret_cast<ElfW(Addr)>(d) + d->d_un.d_val);
*dp = &_r_debug;
}
break;
case DT_MIPS_RLD_VERSION:
case DT_MIPS_FLAGS:
case DT_MIPS_BASE_ADDRESS:
case DT_MIPS_UNREFEXTNO:
break;
case DT_MIPS_SYMTABNO:
mips_symtabno_ = d->d_un.d_val;
break;
case DT_MIPS_LOCAL_GOTNO:
mips_local_gotno_ = d->d_un.d_val;
break;
case DT_MIPS_GOTSYM:
mips_gotsym_ = d->d_un.d_val;
break;
#endif
// Ignored: "Its use has been superseded by the DF_BIND_NOW flag"
case DT_BIND_NOW:
break;
case DT_VERSYM:
versym_ = reinterpret_cast<ElfW(Versym)*>(load_bias + d->d_un.d_ptr);
break;
case DT_VERDEF:
verdef_ptr_ = load_bias + d->d_un.d_ptr;
break;
case DT_VERDEFNUM:
verdef_cnt_ = d->d_un.d_val;
break;
case DT_VERNEED:
verneed_ptr_ = load_bias + d->d_un.d_ptr;
break;
case DT_VERNEEDNUM:
verneed_cnt_ = d->d_un.d_val;
break;
default:
if (!relocating_linker) {
DL_WARN("%s: unused DT entry: type %p arg %p", get_realpath(),
reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
}
break;
}
}
// second pass - parse entries relying on strtab
for (ElfW(Dyn)* d = dynamic; d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_SONAME) {
soname_ = get_string(d->d_un.d_val);
#if defined(__arm__)
strlcpy(old_name_, soname_, sizeof(old_name_));
#endif
break;
}
}
DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
reinterpret_cast<void*>(base), strtab_, symtab_);
// Sanity checks.
if (relocating_linker && needed_count != 0) {
DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
return false;
}
if (nbucket_ == 0 && gnu_nbucket_ == 0) {
DL_ERR("empty/missing DT_HASH/DT_GNU_HASH in \"%s\" "
"(new hash type from the future?)", get_soname());
return false;
}
if (strtab_ == 0) {
DL_ERR("empty/missing DT_STRTAB in \"%s\"", get_soname());
return false;
}
if (symtab_ == 0) {
DL_ERR("empty/missing DT_SYMTAB in \"%s\"", get_soname());
return false;
}
return true;
}
bool soinfo::link_image(const soinfo_list_t& global_group, const soinfo_list_t& local_group,
const android_dlextinfo* extinfo) {
local_group_root_ = local_group.front();
if (local_group_root_ == nullptr) {
local_group_root_ = this;
}
#if !defined(__LP64__)
if (has_text_relocations) {
// Make segments writable to allow text relocations to work properly. We will later call
// phdr_table_protect_segments() after all of them are applied and all constructors are run.
DL_WARN("%s has text relocations. This is wasting memory and prevents "
"security hardening. Please fix.", get_soname());
if (phdr_table_unprotect_segments(phdr, phnum, load_bias) < 0) {
DL_ERR("can't unprotect loadable segments for \"%s\": %s",
get_soname(), strerror(errno));
return false;
}
}
#endif
if (android_relocs_ != nullptr) {
// check signature
if (android_relocs_size_ > 3 &&
android_relocs_[0] == 'A' &&
android_relocs_[1] == 'P' &&
android_relocs_[2] == 'S' &&
android_relocs_[3] == '2') {
DEBUG("[ android relocating %s ]", get_soname());
bool relocated = false;
const uint8_t* packed_relocs = android_relocs_ + 4;
const size_t packed_relocs_size = android_relocs_size_ - 4;
relocated = relocate(
packed_reloc_iterator<sleb128_decoder>(
sleb128_decoder(packed_relocs, packed_relocs_size)),
global_group, local_group);
if (!relocated) {
return false;
}
} else {
DL_ERR("bad android relocation header.");
return false;
}
}
#if defined(USE_RELA)
if (rela_ != nullptr) {
DEBUG("[ relocating %s ]", get_soname());
if (!relocate(plain_reloc_iterator(rela_, rela_count_), global_group, local_group)) {
return false;
}
}
if (plt_rela_ != nullptr) {
DEBUG("[ relocating %s plt ]", get_soname());
if (!relocate(plain_reloc_iterator(plt_rela_, plt_rela_count_), global_group, local_group)) {
return false;
}
}
#else
if (rel_ != nullptr) {
DEBUG("[ relocating %s ]", get_soname());
if (!relocate(plain_reloc_iterator(rel_, rel_count_), global_group, local_group)) {
return false;
}
}
if (plt_rel_ != nullptr) {
DEBUG("[ relocating %s plt ]", get_soname());
if (!relocate(plain_reloc_iterator(plt_rel_, plt_rel_count_), global_group, local_group)) {
return false;
}
}
#endif
#if defined(__mips__)
if (!mips_relocate_got(global_group, local_group)) {
return false;
}
#endif
DEBUG("[ finished linking %s ]", get_soname());
#if !defined(__LP64__)
if (has_text_relocations) {
// All relocations are done, we can protect our segments back to read-only.
if (phdr_table_protect_segments(phdr, phnum, load_bias) < 0) {
DL_ERR("can't protect segments for \"%s\": %s",
get_soname(), strerror(errno));
return false;
}
}
#endif
/* We can also turn on GNU RELRO protection */
if (phdr_table_protect_gnu_relro(phdr, phnum, load_bias) < 0) {
DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
get_soname(), strerror(errno));
return false;
}
/* Handle serializing/sharing the RELRO segment */
if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
if (phdr_table_serialize_gnu_relro(phdr, phnum, load_bias,
extinfo->relro_fd) < 0) {
DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
get_soname(), strerror(errno));
return false;
}
} else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
if (phdr_table_map_gnu_relro(phdr, phnum, load_bias,
extinfo->relro_fd) < 0) {
DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
get_soname(), strerror(errno));
return false;
}
}
notify_gdb_of_load(this);
return true;
}
/*
* This function add vdso to internal dso list.
* It helps to stack unwinding through signal handlers.
* Also, it makes bionic more like glibc.
*/
static void add_vdso(KernelArgumentBlock& args __unused) {
#if defined(AT_SYSINFO_EHDR)
ElfW(Ehdr)* ehdr_vdso = reinterpret_cast<ElfW(Ehdr)*>(args.getauxval(AT_SYSINFO_EHDR));
if (ehdr_vdso == nullptr) {
return;
}
soinfo* si = soinfo_alloc("[vdso]", nullptr, 0, 0);
si->phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<char*>(ehdr_vdso) + ehdr_vdso->e_phoff);
si->phnum = ehdr_vdso->e_phnum;
si->base = reinterpret_cast<ElfW(Addr)>(ehdr_vdso);
si->size = phdr_table_get_load_size(si->phdr, si->phnum);
si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
si->prelink_image();
si->link_image(g_empty_list, soinfo::soinfo_list_t::make_list(si), nullptr);
#endif
}
/*
* This is linker soinfo for GDB. See details below.
*/
#if defined(__LP64__)
#define LINKER_PATH "/system/bin/linker64"
#else
#define LINKER_PATH "/system/bin/linker"
#endif
// This is done to avoid calling c-tor prematurely
// because soinfo c-tor needs memory allocator
// which might be initialized after global variables.
static uint8_t linker_soinfo_for_gdb_buf[sizeof(soinfo)] __attribute__((aligned(8)));
static soinfo* linker_soinfo_for_gdb = nullptr;
/* gdb expects the linker to be in the debug shared object list.
* Without this, gdb has trouble locating the linker's ".text"
* and ".plt" sections. Gdb could also potentially use this to
* relocate the offset of our exported 'rtld_db_dlactivity' symbol.
* Don't use soinfo_alloc(), because the linker shouldn't
* be on the soinfo list.
*/
static void init_linker_info_for_gdb(ElfW(Addr) linker_base) {
linker_soinfo_for_gdb = new (linker_soinfo_for_gdb_buf) soinfo(LINKER_PATH, nullptr, 0, 0);
linker_soinfo_for_gdb->base = linker_base;
/*
* Set the dynamic field in the link map otherwise gdb will complain with
* the following:
* warning: .dynamic section for "/system/bin/linker" is not at the
* expected address (wrong library or version mismatch?)
*/
ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_base);
ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_base + elf_hdr->e_phoff);
phdr_table_get_dynamic_section(phdr, elf_hdr->e_phnum, linker_base,
&linker_soinfo_for_gdb->dynamic, nullptr);
insert_soinfo_into_debug_map(linker_soinfo_for_gdb);
}
extern "C" int __system_properties_init(void);
/*
* This code is called after the linker has linked itself and
* fixed it's own GOT. It is safe to make references to externs
* and other non-local data at this point.
*/
static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(Addr) linker_base) {
#if TIMING
struct timeval t0, t1;
gettimeofday(&t0, 0);
#endif
// Initialize environment functions, and get to the ELF aux vectors table.
linker_env_init(args);
// Initialize system properties
__system_properties_init(); // may use 'environ'
// If this is a setuid/setgid program, close the security hole described in
// ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:23.stdio.asc
if (get_AT_SECURE()) {
nullify_closed_stdio();
}
debuggerd_init();
// Get a few environment variables.
const char* LD_DEBUG = linker_env_get("LD_DEBUG");
if (LD_DEBUG != nullptr) {
g_ld_debug_verbosity = atoi(LD_DEBUG);
}
// Normally, these are cleaned by linker_env_init, but the test
// doesn't cost us anything.
const char* ldpath_env = nullptr;
const char* ldpreload_env = nullptr;
if (!get_AT_SECURE()) {
ldpath_env = linker_env_get("LD_LIBRARY_PATH");
ldpreload_env = linker_env_get("LD_PRELOAD");
}
#if !defined(__LP64__)
if (personality(PER_LINUX32) == -1) {
__libc_fatal("error setting PER_LINUX32 personality: %s", strerror(errno));
}
#endif
INFO("[ android linker & debugger ]");
soinfo* si = soinfo_alloc(args.argv[0], nullptr, 0, RTLD_GLOBAL);
if (si == nullptr) {
exit(EXIT_FAILURE);
}
/* bootstrap the link map, the main exe always needs to be first */
si->set_main_executable();
link_map* map = &(si->link_map_head);
map->l_addr = 0;
map->l_name = args.argv[0];
map->l_prev = nullptr;
map->l_next = nullptr;
_r_debug.r_map = map;
r_debug_tail = map;
init_linker_info_for_gdb(linker_base);
// Extract information passed from the kernel.
si->phdr = reinterpret_cast<ElfW(Phdr)*>(args.getauxval(AT_PHDR));
si->phnum = args.getauxval(AT_PHNUM);
si->entry = args.getauxval(AT_ENTRY);
/* Compute the value of si->base. We can't rely on the fact that
* the first entry is the PHDR because this will not be true
* for certain executables (e.g. some in the NDK unit test suite)
*/
si->base = 0;
si->size = phdr_table_get_load_size(si->phdr, si->phnum);
si->load_bias = 0;
for (size_t i = 0; i < si->phnum; ++i) {
if (si->phdr[i].p_type == PT_PHDR) {
si->load_bias = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_vaddr;
si->base = reinterpret_cast<ElfW(Addr)>(si->phdr) - si->phdr[i].p_offset;
break;
}
}
si->dynamic = nullptr;
ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(si->base);
if (elf_hdr->e_type != ET_DYN) {
__libc_format_fd(2, "error: only position independent executables (PIE) are supported.\n");
exit(EXIT_FAILURE);
}
// Use LD_LIBRARY_PATH and LD_PRELOAD (but only if we aren't setuid/setgid).
parse_LD_LIBRARY_PATH(ldpath_env);
parse_LD_PRELOAD(ldpreload_env);
somain = si;
if (!si->prelink_image()) {
__libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
exit(EXIT_FAILURE);
}
// add somain to global group
si->set_dt_flags_1(si->get_dt_flags_1() | DF_1_GLOBAL);
// Load ld_preloads and dependencies.
StringLinkedList needed_library_name_list;
size_t needed_libraries_count = 0;
size_t ld_preloads_count = 0;
for (const auto& ld_preload_name : g_ld_preload_names) {
needed_library_name_list.push_back(ld_preload_name.c_str());
++needed_libraries_count;
}
for_each_dt_needed(si, [&](const char* name) {
needed_library_name_list.push_back(name);
++needed_libraries_count;
});
const char* needed_library_names[needed_libraries_count];
memset(needed_library_names, 0, sizeof(needed_library_names));
needed_library_name_list.copy_to_array(needed_library_names, needed_libraries_count);
if (needed_libraries_count > 0 &&
!find_libraries(si, needed_library_names, needed_libraries_count, nullptr,
&g_ld_preloads, ld_preloads_count, RTLD_GLOBAL, nullptr)) {
__libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
exit(EXIT_FAILURE);
} else if (needed_libraries_count == 0) {
if (!si->link_image(g_empty_list, soinfo::soinfo_list_t::make_list(si), nullptr)) {
__libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
exit(EXIT_FAILURE);
}
si->increment_ref_count();
}
add_vdso(args);
{
ProtectedDataGuard guard;
si->call_pre_init_constructors();
/* After the prelink_image, the si->load_bias is initialized.
* For so lib, the map->l_addr will be updated in notify_gdb_of_load.
* We need to update this value for so exe here. So Unwind_Backtrace
* for some arch like x86 could work correctly within so exe.
*/
map->l_addr = si->load_bias;
si->call_constructors();
}
#if TIMING
gettimeofday(&t1, nullptr);
PRINT("LINKER TIME: %s: %d microseconds", args.argv[0], (int) (
(((long long)t1.tv_sec * 1000000LL) + (long long)t1.tv_usec) -
(((long long)t0.tv_sec * 1000000LL) + (long long)t0.tv_usec)));
#endif
#if STATS
PRINT("RELO STATS: %s: %d abs, %d rel, %d copy, %d symbol", args.argv[0],
linker_stats.count[kRelocAbsolute],
linker_stats.count[kRelocRelative],
linker_stats.count[kRelocCopy],
linker_stats.count[kRelocSymbol]);
#endif
#if COUNT_PAGES
{
unsigned n;
unsigned i;
unsigned count = 0;
for (n = 0; n < 4096; n++) {
if (bitmask[n]) {
unsigned x = bitmask[n];
#if defined(__LP64__)
for (i = 0; i < 32; i++) {
#else
for (i = 0; i < 8; i++) {
#endif
if (x & 1) {
count++;
}
x >>= 1;
}
}
}
PRINT("PAGES MODIFIED: %s: %d (%dKB)", args.argv[0], count, count * 4);
}
#endif
#if TIMING || STATS || COUNT_PAGES
fflush(stdout);
#endif
TRACE("[ Ready to execute '%s' @ %p ]", si->get_soname(), reinterpret_cast<void*>(si->entry));
return si->entry;
}
/* Compute the load-bias of an existing executable. This shall only
* be used to compute the load bias of an executable or shared library
* that was loaded by the kernel itself.
*
* Input:
* elf -> address of ELF header, assumed to be at the start of the file.
* Return:
* load bias, i.e. add the value of any p_vaddr in the file to get
* the corresponding address in memory.
*/
static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf) {
ElfW(Addr) offset = elf->e_phoff;
const ElfW(Phdr)* phdr_table = reinterpret_cast<const ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(elf) + offset);
const ElfW(Phdr)* phdr_end = phdr_table + elf->e_phnum;
for (const ElfW(Phdr)* phdr = phdr_table; phdr < phdr_end; phdr++) {
if (phdr->p_type == PT_LOAD) {
return reinterpret_cast<ElfW(Addr)>(elf) + phdr->p_offset - phdr->p_vaddr;
}
}
return 0;
}
extern "C" void _start();
/*
* This is the entry point for the linker, called from begin.S. This
* method is responsible for fixing the linker's own relocations, and
* then calling __linker_init_post_relocation().
*
* Because this method is called before the linker has fixed it's own
* relocations, any attempt to reference an extern variable, extern
* function, or other GOT reference will generate a segfault.
*/
extern "C" ElfW(Addr) __linker_init(void* raw_args) {
KernelArgumentBlock args(raw_args);
ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
ElfW(Addr) entry_point = args.getauxval(AT_ENTRY);
ElfW(Ehdr)* elf_hdr = reinterpret_cast<ElfW(Ehdr)*>(linker_addr);
ElfW(Phdr)* phdr = reinterpret_cast<ElfW(Phdr)*>(linker_addr + elf_hdr->e_phoff);
soinfo linker_so(nullptr, nullptr, 0, 0);
// If the linker is not acting as PT_INTERP entry_point is equal to
// _start. Which means that the linker is running as an executable and
// already linked by PT_INTERP.
//
// This happens when user tries to run 'adb shell /system/bin/linker'
// see also https://code.google.com/p/android/issues/detail?id=63174
if (reinterpret_cast<ElfW(Addr)>(&_start) == entry_point) {
__libc_fatal("This is %s, the helper program for shared library executables.\n", args.argv[0]);
}
linker_so.base = linker_addr;
linker_so.size = phdr_table_get_load_size(phdr, elf_hdr->e_phnum);
linker_so.load_bias = get_elf_exec_load_bias(elf_hdr);
linker_so.dynamic = nullptr;
linker_so.phdr = phdr;
linker_so.phnum = elf_hdr->e_phnum;
linker_so.set_linker_flag();
// This might not be obvious... The reasons why we pass g_empty_list
// in place of local_group here are (1) we do not really need it, because
// linker is built with DT_SYMBOLIC and therefore relocates its symbols against
// itself without having to look into local_group and (2) allocators
// are not yet initialized, and therefore we cannot use linked_list.push_*
// functions at this point.
if (!(linker_so.prelink_image() && linker_so.link_image(g_empty_list, g_empty_list, nullptr))) {
// It would be nice to print an error message, but if the linker
// can't link itself, there's no guarantee that we'll be able to
// call write() (because it involves a GOT reference). We may as
// well try though...
const char* msg = "CANNOT LINK EXECUTABLE: ";
write(2, msg, strlen(msg));
write(2, __linker_dl_err_buf, strlen(__linker_dl_err_buf));
write(2, "\n", 1);
_exit(EXIT_FAILURE);
}
__libc_init_tls(args);
// Initialize the linker's own global variables
linker_so.call_constructors();
// Initialize static variables. Note that in order to
// get correct libdl_info we need to call constructors
// before get_libdl_info().
solist = get_libdl_info();
sonext = get_libdl_info();
// We have successfully fixed our own relocations. It's safe to run
// the main part of the linker now.
args.abort_message_ptr = &g_abort_message;
ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
INFO("[ jumping to _start ]");
// Return the address that the calling assembly stub should jump to.
return start_address;
}
Reference in a new issue View git blame Copy permalink