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bdcab25ee6
bionic/linker/linker.cpp
Elliott Hughes 1a58629340 Remove an unused parameter from the dlopen implementation. 
Change-Id: I9297913a743bb570b48ebbe594ff711a481e89e0
2014-06-03 16:23:08 -07:00

2263 lines
76 KiB
C++
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/*
* Copyright (C) 2008, 2009 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/stat.h>
#include <unistd.h>
// Private C library headers.
#include "private/bionic_tls.h"
#include "private/KernelArgumentBlock.h"
#include "private/ScopedPthreadMutexLocker.h"
#include "linker.h"
#include "linker_debug.h"
#include "linker_environ.h"
#include "linker_phdr.h"
#include "linker_allocator.h"
/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<<
*
* Do NOT use malloc() and friends or pthread_*() code here.
* Don't use printf() either; it's caused mysterious memory
* corruption in the past.
* The linker runs before we bring up libc and it's easiest
* to make sure it does not depend on any complex libc features
*
* open issues / todo:
*
* - cleaner error reporting
* - after linking, set as much stuff as possible to READONLY
* and NOEXEC
*/
#if defined(__LP64__)
#define SEARCH_NAME(x) x
#else
// Nvidia drivers are relying on the bug:
// http://code.google.com/p/android/issues/detail?id=6670
// so we continue to use base-name lookup for lp32
static const char* get_base_name(const char* name) {
const char* bname = strrchr(name, '/');
return bname ? bname + 1 : name;
}
#define SEARCH_NAME(x) get_base_name(x)
#endif
static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo);
static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
static LinkerAllocator<soinfo> g_soinfo_allocator;
static LinkerAllocator<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
NULL
};
#define LDPATH_BUFSIZE (LDPATH_MAX*64)
#define LDPATH_MAX 8
#define LDPRELOAD_BUFSIZE (LDPRELOAD_MAX*64)
#define LDPRELOAD_MAX 8
static char g_ld_library_paths_buffer[LDPATH_BUFSIZE];
static const char* g_ld_library_paths[LDPATH_MAX + 1];
static char g_ld_preloads_buffer[LDPRELOAD_BUFSIZE];
static const char* g_ld_preload_names[LDPRELOAD_MAX + 1];
static soinfo* g_ld_preloads[LDPRELOAD_MAX + 1];
__LIBC_HIDDEN__ int g_ld_debug_verbosity;
__LIBC_HIDDEN__ abort_msg_t* g_abort_message = NULL; // For debuggerd.
enum RelocationKind {
kRelocAbsolute = 0,
kRelocRelative,
kRelocCopy,
kRelocSymbol,
kRelocMax
};
#if STATS
struct linker_stats_t {
int count[kRelocMax];
};
static linker_stats_t linker_stats;
static void count_relocation(RelocationKind kind) {
++linker_stats.count[kind];
}
#else
static void count_relocation(RelocationKind) {
}
#endif
#if COUNT_PAGES
static unsigned bitmask[4096];
#if defined(__LP64__)
#define MARK(offset) \
do { \
if ((((offset) >> 12) >> 5) < 4096) \
bitmask[((offset) >> 12) >> 5] |= (1 << (((offset) >> 12) & 31)); \
} while (0)
#else
#define MARK(offset) \
do { \
bitmask[((offset) >> 12) >> 3] |= (1 << (((offset) >> 12) & 7)); \
} while (0)
#endif
#else
#define MARK(x) do {} while (0)
#endif
// You shouldn't try to call memory-allocating functions in the dynamic linker.
// Guard against the most obvious ones.
#define DISALLOW_ALLOCATION(return_type, name, ...) \
return_type name __VA_ARGS__ \
{ \
const char* msg = "ERROR: " #name " called from the dynamic linker!\n"; \
__libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg); \
write(2, msg, strlen(msg)); \
abort(); \
}
DISALLOW_ALLOCATION(void*, malloc, (size_t u __unused));
DISALLOW_ALLOCATION(void, free, (void* u __unused));
DISALLOW_ALLOCATION(void*, realloc, (void* u1 __unused, size_t u2 __unused));
DISALLOW_ALLOCATION(void*, calloc, (size_t u1 __unused, size_t u2 __unused));
static char tmp_err_buf[768];
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, NULL, 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;
map->l_name = reinterpret_cast<char*>(info->name);
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->flags & FLAG_EXE) {
// 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->flags & FLAG_EXE) {
// 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 void protect_data(int protection) {
g_soinfo_allocator.protect_all(protection);
g_soinfo_links_allocator.protect_all(protection);
}
static soinfo* soinfo_alloc(const char* name, struct stat* file_stat) {
if (strlen(name) >= SOINFO_NAME_LEN) {
DL_ERR("library name \"%s\" too long", name);
return NULL;
}
soinfo* si = g_soinfo_allocator.alloc();
// Initialize the new element.
memset(si, 0, sizeof(soinfo));
strlcpy(si->name, name, sizeof(si->name));
si->flags = FLAG_NEW_SOINFO;
if (file_stat != NULL) {
si->set_st_dev(file_stat->st_dev);
si->set_st_ino(file_stat->st_ino);
}
sonext->next = si;
sonext = si;
TRACE("name %s: allocated soinfo @ %p", name, si);
return si;
}
static void soinfo_free(soinfo* si) {
if (si == NULL) {
return;
}
if (si->base != 0 && si->size != 0) {
munmap(reinterpret_cast<void*>(si->base), si->size);
}
soinfo *prev = NULL, *trav;
TRACE("name %s: freeing soinfo @ %p", si->name, si);
for (trav = solist; trav != NULL; trav = trav->next) {
if (trav == si)
break;
prev = trav;
}
if (trav == NULL) {
/* si was not in solist */
DL_ERR("name \"%s\" is not in solist!", si->name);
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,
const char** array, char* buf, size_t buf_size, size_t max_count) {
if (path == NULL) {
return;
}
size_t len = strlcpy(buf, path, buf_size);
size_t i = 0;
char* buf_p = buf;
while (i < max_count && (array[i] = strsep(&buf_p, delimiters))) {
if (*array[i] != '\0') {
++i;
}
}
// Forget the last path if we had to truncate; this occurs if the 2nd to
// last char isn't '\0' (i.e. wasn't originally a delimiter).
if (i > 0 && len >= buf_size && buf[buf_size - 2] != '\0') {
array[i - 1] = NULL;
} else {
array[i] = NULL;
}
}
static void parse_LD_LIBRARY_PATH(const char* path) {
parse_path(path, ":", g_ld_library_paths,
g_ld_library_paths_buffer, sizeof(g_ld_library_paths_buffer), LDPATH_MAX);
}
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,
g_ld_preloads_buffer, sizeof(g_ld_preloads_buffer), LDPRELOAD_MAX);
}
#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) {
unsigned addr = (unsigned)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 (_Unwind_Ptr)si->ARM_exidx;
}
}
*pcount = 0;
return NULL;
}
#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 != NULL; 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;
}
static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) {
ElfW(Sym)* symtab = si->symtab;
const char* strtab = si->strtab;
TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd",
name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) {
ElfW(Sym)* s = symtab + n;
if (strcmp(strtab + s->st_name, name)) continue;
/* only concern ourselves with global and weak symbol definitions */
switch (ELF_ST_BIND(s->st_info)) {
case STB_GLOBAL:
case STB_WEAK:
if (s->st_shndx == SHN_UNDEF) {
continue;
}
TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
name, si->name, reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
return s;
}
}
return NULL;
}
static unsigned elfhash(const char* _name) {
const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
unsigned h = 0, g;
while (*name) {
h = (h << 4) + *name++;
g = h & 0xf0000000;
h ^= g;
h ^= g >> 24;
}
return h;
}
static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, soinfo* needed[]) {
unsigned elf_hash = elfhash(name);
ElfW(Sym)* s = NULL;
if (si != NULL && somain != NULL) {
/*
* Local scope is executable scope. Just start looking into it right away
* for the shortcut.
*/
if (si == somain) {
s = soinfo_elf_lookup(si, elf_hash, name);
if (s != NULL) {
*lsi = si;
goto done;
}
} else {
/* Order of symbol lookup is controlled by DT_SYMBOLIC flag */
/*
* If this object was built with symbolic relocations disabled, the
* first place to look to resolve external references is the main
* executable.
*/
if (!si->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in executable %s",
si->name, name, somain->name);
s = soinfo_elf_lookup(somain, elf_hash, name);
if (s != NULL) {
*lsi = somain;
goto done;
}
}
/* Look for symbols in the local scope (the object who is
* searching). This happens with C++ templates on x86 for some
* reason.
*
* Notes on weak symbols:
* The ELF specs are ambiguous about treatment of weak definitions in
* dynamic linking. Some systems return the first definition found
* and some the first non-weak definition. This is system dependent.
* Here we return the first definition found for simplicity. */
s = soinfo_elf_lookup(si, elf_hash, name);
if (s != NULL) {
*lsi = si;
goto done;
}
/*
* If this object was built with -Bsymbolic and symbol is not found
* in the local scope, try to find the symbol in the main executable.
*/
if (si->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in executable %s after local scope",
si->name, name, somain->name);
s = soinfo_elf_lookup(somain, elf_hash, name);
if (s != NULL) {
*lsi = somain;
goto done;
}
}
}
}
/* Next, look for it in the preloads list */
for (int i = 0; g_ld_preloads[i] != NULL; i++) {
s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
if (s != NULL) {
*lsi = g_ld_preloads[i];
goto done;
}
}
for (int i = 0; needed[i] != NULL; i++) {
DEBUG("%s: looking up %s in %s",
si->name, name, needed[i]->name);
s = soinfo_elf_lookup(needed[i], elf_hash, name);
if (s != NULL) {
*lsi = needed[i];
goto done;
}
}
done:
if (s != NULL) {
TRACE_TYPE(LOOKUP, "si %s sym %s s->st_value = %p, "
"found in %s, base = %p, load bias = %p",
si->name, name, reinterpret_cast<void*>(s->st_value),
(*lsi)->name, reinterpret_cast<void*>((*lsi)->base),
reinterpret_cast<void*>((*lsi)->load_bias));
return s;
}
return NULL;
}
/* This is used by dlsym(3). It performs symbol lookup only within the
specified soinfo object and not in any of its dependencies.
TODO: Only looking in the specified soinfo seems wrong. dlsym(3) says
that it should do a breadth first search through the dependency
tree. This agrees with the ELF spec (aka System V Application
Binary Interface) where in Chapter 5 it discuss resolving "Shared
Object Dependencies" in breadth first search order.
*/
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) {
return soinfo_elf_lookup(si, elfhash(name), name);
}
/* 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).
*/
ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
unsigned elf_hash = elfhash(name);
if (start == NULL) {
start = solist;
}
ElfW(Sym)* s = NULL;
for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) {
s = soinfo_elf_lookup(si, elf_hash, name);
if (s != NULL) {
*found = si;
break;
}
}
if (s != NULL) {
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 != NULL; si = si->next) {
if (address >= si->base && address - si->base < si->size) {
return si;
}
}
return NULL;
}
ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
// Search the library's symbol table for any defined symbol which
// contains this address.
for (size_t i = 0; i < si->nchain; ++i) {
ElfW(Sym)* sym = &si->symtab[i];
if (sym->st_shndx != SHN_UNDEF &&
soaddr >= sym->st_value &&
soaddr < sym->st_value + sym->st_size) {
return sym;
}
}
return NULL;
}
static int open_library_on_path(const char* name, const char* const paths[]) {
char buf[512];
for (size_t i = 0; paths[i] != NULL; ++i) {
int n = __libc_format_buffer(buf, sizeof(buf), "%s/%s", paths[i], name);
if (n < 0 || n >= static_cast<int>(sizeof(buf))) {
PRINT("Warning: ignoring very long library path: %s/%s", paths[i], name);
continue;
}
int fd = TEMP_FAILURE_RETRY(open(buf, O_RDONLY | O_CLOEXEC));
if (fd != -1) {
return fd;
}
}
return -1;
}
static int open_library(const char* name) {
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, '/') != NULL) {
int fd = TEMP_FAILURE_RETRY(open(name, O_RDONLY | O_CLOEXEC));
if (fd != -1) {
return fd;
}
// ...but nvidia binary blobs (at least) rely on this behavior, so fall through for now.
#if defined(__LP64__)
// TODO: uncomment this after bug b/7465467 is fixed.
// return -1;
#endif
}
// Otherwise we try LD_LIBRARY_PATH first, and fall back to the built-in well known paths.
int fd = open_library_on_path(name, g_ld_library_paths);
if (fd == -1) {
fd = open_library_on_path(name, kDefaultLdPaths);
}
return fd;
}
static soinfo* load_library(const char* name, int dlflags, const android_dlextinfo* extinfo) {
// Open the file.
int fd = open_library(name);
if (fd == -1) {
DL_ERR("library \"%s\" not found", name);
return NULL;
}
ElfReader elf_reader(name, fd);
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 NULL;
}
// Check for symlink and other situations where
// file can have different names.
for (soinfo* si = solist; si != NULL; 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) {
TRACE("library \"%s\" is already loaded under different name/path \"%s\" - will return existing soinfo", name, si->name);
return si;
}
}
if ((dlflags & RTLD_NOLOAD) != 0) {
return NULL;
}
// Read the ELF header and load the segments.
if (!elf_reader.Load(extinfo)) {
return NULL;
}
soinfo* si = soinfo_alloc(SEARCH_NAME(name), &file_stat);
if (si == NULL) {
return NULL;
}
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();
// At this point we know that whatever is loaded @ base is a valid ELF
// shared library whose segments are properly mapped in.
TRACE("[ find_library_internal base=%p size=%zu name='%s' ]",
reinterpret_cast<void*>(si->base), si->size, si->name);
if (!soinfo_link_image(si, extinfo)) {
soinfo_free(si);
return NULL;
}
return si;
}
static soinfo *find_loaded_library_by_name(const char* name) {
const char* search_name = SEARCH_NAME(name);
for (soinfo* si = solist; si != NULL; si = si->next) {
if (!strcmp(search_name, si->name)) {
return si;
}
}
return NULL;
}
static soinfo* find_library_internal(const char* name, int dlflags, const android_dlextinfo* extinfo) {
if (name == NULL) {
return somain;
}
soinfo* si = find_loaded_library_by_name(name);
// Library might still be loaded, the accurate detection
// of this fact is done by load_library
if (si == NULL) {
TRACE("[ '%s' has not been found by name. Trying harder...]", name);
si = load_library(name, dlflags, extinfo);
}
if (si != NULL && (si->flags & FLAG_LINKED) == 0) {
DL_ERR("recursive link to \"%s\"", si->name);
return NULL;
}
return si;
}
static soinfo* find_library(const char* name, int dlflags, const android_dlextinfo* extinfo) {
soinfo* si = find_library_internal(name, dlflags, extinfo);
if (si != NULL) {
si->ref_count++;
}
return si;
}
static void soinfo_unload(soinfo* si) {
if (si->ref_count == 1) {
TRACE("unloading '%s'", si->name);
si->CallDestructors();
if ((si->flags | FLAG_NEW_SOINFO) != 0) {
si->get_children().for_each([&] (soinfo* child) {
TRACE("%s needs to unload %s", si->name, child->name);
soinfo_unload(child);
});
} else {
for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_NEEDED) {
const char* library_name = si->strtab + d->d_un.d_val;
TRACE("%s needs to unload %s", si->name, library_name);
soinfo* needed = find_library(library_name, RTLD_NOLOAD, NULL);
if (needed != NULL) {
soinfo_unload(needed);
} else {
// 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->name);
}
}
}
}
notify_gdb_of_unload(si);
si->ref_count = 0;
soinfo_free(si);
} else {
si->ref_count--;
TRACE("not unloading '%s', decrementing ref_count to %zd", si->name, si->ref_count);
}
}
void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
snprintf(buffer, buffer_size, "%s:%s", kDefaultLdPaths[0], kDefaultLdPaths[1]);
}
void do_android_update_LD_LIBRARY_PATH(const char* ld_library_path) {
if (!get_AT_SECURE()) {
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_NOLOAD)) != 0) {
DL_ERR("invalid flags to dlopen: %x", flags);
return NULL;
}
if (extinfo != NULL && ((extinfo->flags & ~(ANDROID_DLEXT_VALID_FLAG_BITS)) != 0)) {
DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags);
return NULL;
}
protect_data(PROT_READ | PROT_WRITE);
soinfo* si = find_library(name, flags, extinfo);
if (si != NULL) {
si->CallConstructors();
}
protect_data(PROT_READ);
return si;
}
void do_dlclose(soinfo* si) {
protect_data(PROT_READ | PROT_WRITE);
soinfo_unload(si);
protect_data(PROT_READ);
}
#if defined(USE_RELA)
static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
ElfW(Sym)* s;
soinfo* lsi;
for (size_t idx = 0; idx < count; ++idx, ++rela) {
unsigned type = ELFW(R_TYPE)(rela->r_info);
unsigned sym = ELFW(R_SYM)(rela->r_info);
ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias);
ElfW(Addr) sym_addr = 0;
const char* sym_name = NULL;
DEBUG("Processing '%s' relocation at index %zd", si->name, idx);
if (type == 0) { // R_*_NONE
continue;
}
if (sym != 0) {
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (s == NULL) {
// We only allow an undefined symbol if this is a weak reference...
s = &si->symtab[sym];
if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name);
return -1;
}
/* 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) {
#if defined(__aarch64__)
case R_AARCH64_JUMP_SLOT:
case R_AARCH64_GLOB_DAT:
case R_AARCH64_ABS64:
case R_AARCH64_ABS32:
case R_AARCH64_ABS16:
case R_AARCH64_RELATIVE:
/*
* 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;
#elif defined(__x86_64__)
case R_X86_64_JUMP_SLOT:
case R_X86_64_GLOB_DAT:
case R_X86_64_32:
case R_X86_64_64:
case R_X86_64_RELATIVE:
// No need to do anything.
break;
case R_X86_64_PC32:
sym_addr = reloc;
break;
#endif
default:
DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rela, idx);
return -1;
}
} else {
// We got a definition.
sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias);
}
count_relocation(kRelocSymbol);
} else {
s = NULL;
}
switch (type) {
#if defined(__aarch64__)
case R_AARCH64_JUMP_SLOT:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %16llx <- %16llx %s\n",
reloc, (sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
break;
case R_AARCH64_GLOB_DAT:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO GLOB_DAT %16llx <- %16llx %s\n",
reloc, (sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = (sym_addr + rela->r_addend);
break;
case R_AARCH64_ABS64:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO ABS64 %16llx <- %16llx %s\n",
reloc, (sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
break;
case R_AARCH64_ABS32:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO ABS32 %16llx <- %16llx %s\n",
reloc, (sym_addr + rela->r_addend), sym_name);
if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
(*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
static_cast<ElfW(Addr)>(INT32_MIN),
static_cast<ElfW(Addr)>(UINT32_MAX));
return -1;
}
break;
case R_AARCH64_ABS16:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO ABS16 %16llx <- %16llx %s\n",
reloc, (sym_addr + rela->r_addend), sym_name);
if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend))) &&
((*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
(*reinterpret_cast<ElfW(Addr)*>(reloc) + (sym_addr + rela->r_addend)),
static_cast<ElfW(Addr)>(INT16_MIN),
static_cast<ElfW(Addr)>(UINT16_MAX));
return -1;
}
break;
case R_AARCH64_PREL64:
count_relocation(kRelocRelative);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO REL64 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) += (sym_addr + rela->r_addend) - rela->r_offset;
break;
case R_AARCH64_PREL32:
count_relocation(kRelocRelative);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO REL32 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
if ((static_cast<ElfW(Addr)>(INT32_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT32_MAX))) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
(*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
static_cast<ElfW(Addr)>(INT32_MIN),
static_cast<ElfW(Addr)>(UINT32_MAX));
return -1;
}
break;
case R_AARCH64_PREL16:
count_relocation(kRelocRelative);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO REL16 %16llx <- %16llx - %16llx %s\n",
reloc, (sym_addr + rela->r_addend), rela->r_offset, sym_name);
if ((static_cast<ElfW(Addr)>(INT16_MIN) <= (*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset))) &&
((*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)) <= static_cast<ElfW(Addr)>(UINT16_MAX))) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += ((sym_addr + rela->r_addend) - rela->r_offset);
} else {
DL_ERR("0x%016llx out of range 0x%016llx to 0x%016llx",
(*reinterpret_cast<ElfW(Addr)*>(reloc) + ((sym_addr + rela->r_addend) - rela->r_offset)),
static_cast<ElfW(Addr)>(INT16_MIN),
static_cast<ElfW(Addr)>(UINT16_MAX));
return -1;
}
break;
case R_AARCH64_RELATIVE:
count_relocation(kRelocRelative);
MARK(rela->r_offset);
if (sym) {
DL_ERR("odd RELATIVE form...");
return -1;
}
TRACE_TYPE(RELO, "RELO RELATIVE %16llx <- %16llx\n",
reloc, (si->base + rela->r_addend));
*reinterpret_cast<ElfW(Addr)*>(reloc) = (si->base + rela->r_addend);
break;
case R_AARCH64_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 4.7.1.10 "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", si->name);
return -1;
case R_AARCH64_TLS_TPREL64:
TRACE_TYPE(RELO, "RELO TLS_TPREL64 *** %16llx <- %16llx - %16llx\n",
reloc, (sym_addr + rela->r_addend), rela->r_offset);
break;
case R_AARCH64_TLS_DTPREL32:
TRACE_TYPE(RELO, "RELO TLS_DTPREL32 *** %16llx <- %16llx - %16llx\n",
reloc, (sym_addr + rela->r_addend), rela->r_offset);
break;
#elif defined(__x86_64__)
case R_X86_64_JUMP_SLOT:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
break;
case R_X86_64_GLOB_DAT:
count_relocation(kRelocAbsolute);
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO GLOB_DAT %08zx <- %08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
break;
case R_X86_64_RELATIVE:
count_relocation(kRelocRelative);
MARK(rela->r_offset);
if (sym) {
DL_ERR("odd RELATIVE form...");
return -1;
}
TRACE_TYPE(RELO, "RELO RELATIVE %08zx <- +%08zx", static_cast<size_t>(reloc),
static_cast<size_t>(si->base));
*reinterpret_cast<ElfW(Addr)*>(reloc) = si->base + rela->r_addend;
break;
case R_X86_64_32:
count_relocation(kRelocRelative);
MARK(rela->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 + rela->r_addend;
break;
case R_X86_64_64:
count_relocation(kRelocRelative);
MARK(rela->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 + rela->r_addend;
break;
case R_X86_64_PC32:
count_relocation(kRelocRelative);
MARK(rela->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 + rela->r_addend - reloc;
break;
#endif
default:
DL_ERR("unknown reloc type %d @ %p (%zu)", type, rela, idx);
return -1;
}
}
return 0;
}
#else // REL, not RELA.
static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) {
ElfW(Sym)* s;
soinfo* lsi;
for (size_t idx = 0; idx < count; ++idx, ++rel) {
unsigned type = ELFW(R_TYPE)(rel->r_info);
// TODO: don't use unsigned for 'sym'. Use uint32_t or ElfW(Addr) instead.
unsigned sym = ELFW(R_SYM)(rel->r_info);
ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias);
ElfW(Addr) sym_addr = 0;
const char* sym_name = NULL;
DEBUG("Processing '%s' relocation at index %zd", si->name, idx);
if (type == 0) { // R_*_NONE
continue;
}
if (sym != 0) {
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (s == NULL) {
// We only allow an undefined symbol if this is a weak reference...
s = &si->symtab[sym];
if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
DL_ERR("cannot locate symbol \"%s\" referenced by \"%s\"...", sym_name, si->name);
return -1;
}
/* 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) {
#if defined(__arm__)
case R_ARM_JUMP_SLOT:
case R_ARM_GLOB_DAT:
case R_ARM_ABS32:
case R_ARM_RELATIVE: /* Don't care. */
// sym_addr was initialized to be zero above or relocation
// code below does not care about value of sym_addr.
// No need to do anything.
break;
#elif defined(__i386__)
case R_386_JMP_SLOT:
case R_386_GLOB_DAT:
case R_386_32:
case R_386_RELATIVE: /* Don't care. */
// sym_addr was initialized to be zero above or relocation
// code below does not care about value of sym_addr.
// No need to do anything.
break;
case R_386_PC32:
sym_addr = reloc;
break;
#endif
#if defined(__arm__)
case R_ARM_COPY:
// Fall through. Can't really copy if weak symbol is not found at run-time.
#endif
default:
DL_ERR("unknown weak reloc type %d @ %p (%zu)", type, rel, idx);
return -1;
}
} else {
// We got a definition.
sym_addr = static_cast<ElfW(Addr)>(s->st_value + lsi->load_bias);
}
count_relocation(kRelocSymbol);
} else {
s = NULL;
}
switch (type) {
#if defined(__arm__)
case R_ARM_JUMP_SLOT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
break;
case R_ARM_GLOB_DAT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
break;
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 4.7.1.10 "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", si->name);
return -1;
#elif defined(__i386__)
case R_386_JMP_SLOT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
break;
case R_386_GLOB_DAT:
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO GLOB_DAT %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
break;
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;
#elif defined(__mips__)
case R_MIPS_REL32:
#if defined(__LP64__)
// MIPS Elf64_Rel entries contain compound relocations
// We only handle the R_MIPS_NONE|R_MIPS_64|R_MIPS_REL32 case
if (ELF64_R_TYPE2(rel->r_info) != R_MIPS_64 ||
ELF64_R_TYPE3(rel->r_info) != R_MIPS_NONE) {
DL_ERR("Unexpected compound relocation type:%d type2:%d type3:%d @ %p (%zu)",
type, (unsigned)ELF64_R_TYPE2(rel->r_info),
(unsigned)ELF64_R_TYPE3(rel->r_info), rel, idx);
return -1;
}
#endif
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO REL32 %08zx <- %08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr), sym_name ? sym_name : "*SECTIONHDR*");
if (s) {
*reinterpret_cast<ElfW(Addr)*>(reloc) += sym_addr;
} else {
*reinterpret_cast<ElfW(Addr)*>(reloc) += si->base;
}
break;
#endif
#if defined(__arm__)
case R_ARM_RELATIVE:
#elif defined(__i386__)
case R_386_RELATIVE:
#endif
count_relocation(kRelocRelative);
MARK(rel->r_offset);
if (sym) {
DL_ERR("odd RELATIVE form...");
return -1;
}
TRACE_TYPE(RELO, "RELO RELATIVE %p <- +%p",
reinterpret_cast<void*>(reloc), reinterpret_cast<void*>(si->base));
*reinterpret_cast<ElfW(Addr)*>(reloc) += si->base;
break;
default:
DL_ERR("unknown reloc type %d @ %p (%zu)", type, rel, idx);
return -1;
}
}
return 0;
}
#endif
#if defined(__mips__)
static bool mips_relocate_got(soinfo* si, soinfo* needed[]) {
ElfW(Addr)** got = si->plt_got;
if (got == NULL) {
return true;
}
unsigned local_gotno = si->mips_local_gotno;
unsigned gotsym = si->mips_gotsym;
unsigned symtabno = si->mips_symtabno;
ElfW(Sym)* symtab = si->symtab;
// got[0] is the address of the lazy resolver function.
// got[1] may be used for a GNU extension.
// Set it to a recognizable address in case someone calls it (should be _rtld_bind_start).
// FIXME: maybe this should be in a separate routine?
if ((si->flags & FLAG_LINKER) == 0) {
size_t g = 0;
got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadbeef);
if (reinterpret_cast<intptr_t>(got[g]) < 0) {
got[g++] = reinterpret_cast<ElfW(Addr)*>(0xdeadfeed);
}
// Relocate the local GOT entries.
for (; g < local_gotno; g++) {
got[g] = reinterpret_cast<ElfW(Addr)*>(reinterpret_cast<uintptr_t>(got[g]) + si->load_bias);
}
}
// Now for the global GOT entries...
ElfW(Sym)* sym = symtab + gotsym;
got = si->plt_got + local_gotno;
for (size_t g = gotsym; g < symtabno; g++, sym++, got++) {
// This is an undefined reference... try to locate it.
const char* sym_name = si->strtab + sym->st_name;
soinfo* lsi;
ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (s == NULL) {
// We only allow an undefined symbol if this is a weak reference.
s = &symtab[g];
if (ELF_ST_BIND(s->st_info) != STB_WEAK) {
DL_ERR("cannot locate \"%s\"...", sym_name);
return false;
}
*got = 0;
} else {
// FIXME: is this sufficient?
// For reference see NetBSD link loader
// http://cvsweb.netbsd.org/bsdweb.cgi/src/libexec/ld.elf_so/arch/mips/mips_reloc.c?rev=1.53&content-type=text/x-cvsweb-markup
*got = reinterpret_cast<ElfW(Addr)*>(lsi->load_bias + s->st_value);
}
}
return true;
}
#endif
void soinfo::CallArray(const char* array_name __unused, linker_function_t* functions, size_t count, bool reverse) {
if (functions == NULL) {
return;
}
TRACE("[ Calling %s (size %zd) @ %p for '%s' ]", array_name, count, functions, name);
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]);
CallFunction("function", functions[i]);
}
TRACE("[ Done calling %s for '%s' ]", array_name, name);
}
void soinfo::CallFunction(const char* function_name __unused, linker_function_t function) {
if (function == NULL || reinterpret_cast<uintptr_t>(function) == static_cast<uintptr_t>(-1)) {
return;
}
TRACE("[ Calling %s @ %p for '%s' ]", function_name, function, name);
function();
TRACE("[ Done calling %s @ %p for '%s' ]", function_name, function, name);
// The function may have called dlopen(3) or dlclose(3), so we need to ensure our data structures
// are still writable. This happens with our debug malloc (see http://b/7941716).
protect_data(PROT_READ | PROT_WRITE);
}
void soinfo::CallPreInitConstructors() {
// DT_PREINIT_ARRAY functions are called before any other constructors for executables,
// but ignored in a shared library.
CallArray("DT_PREINIT_ARRAY", preinit_array, preinit_array_count, false);
}
void soinfo::CallConstructors() {
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 ((flags & FLAG_EXE) == 0 && preinit_array != NULL) {
// The GNU dynamic linker silently ignores these, but we warn the developer.
PRINT("\"%s\": ignoring %zd-entry DT_PREINIT_ARRAY in shared library!",
name, preinit_array_count);
}
get_children().for_each([] (soinfo* si) {
si->CallConstructors();
});
TRACE("\"%s\": calling constructors", name);
// DT_INIT should be called before DT_INIT_ARRAY if both are present.
CallFunction("DT_INIT", init_func);
CallArray("DT_INIT_ARRAY", init_array, init_array_count, false);
}
void soinfo::CallDestructors() {
TRACE("\"%s\": calling destructors", name);
// DT_FINI_ARRAY must be parsed in reverse order.
CallArray("DT_FINI_ARRAY", fini_array, fini_array_count, true);
// DT_FINI should be called after DT_FINI_ARRAY if both are present.
CallFunction("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 ((this->flags & FLAG_NEW_SOINFO) == 0) {
return;
}
this->children.push_front(child);
child->parents.push_front(this);
}
void soinfo::remove_all_links() {
if ((this->flags & FLAG_NEW_SOINFO) == 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.for_each([&] (const soinfo* child) {
return child == this;
});
});
// 2. Once everything untied - clear local lists.
parents.clear();
children.clear();
}
void soinfo::set_st_dev(dev_t dev) {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return;
}
st_dev = dev;
}
void soinfo::set_st_ino(ino_t ino) {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return;
}
st_ino = ino;
}
dev_t soinfo::get_st_dev() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return 0;
}
return st_dev;
};
ino_t soinfo::get_st_ino() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return 0;
}
return st_ino;
}
// This is a return on get_children() in case
// '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 ((this->flags & FLAG_NEW_SOINFO) == 0) {
return g_empty_list;
}
return this->children;
}
/* 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;
}
static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) {
/* "base" might wrap around UINT32_MAX. */
ElfW(Addr) base = si->load_bias;
const ElfW(Phdr)* phdr = si->phdr;
int phnum = si->phnum;
bool relocating_linker = (si->flags & FLAG_LINKER) != 0;
/* We can't debug anything until the linker is relocated */
if (!relocating_linker) {
INFO("[ linking %s ]", si->name);
DEBUG("si->base = %p si->flags = 0x%08x", reinterpret_cast<void*>(si->base), si->flags);
}
/* Extract dynamic section */
size_t dynamic_count;
ElfW(Word) dynamic_flags;
phdr_table_get_dynamic_section(phdr, phnum, base, &si->dynamic,
&dynamic_count, &dynamic_flags);
if (si->dynamic == NULL) {
if (!relocating_linker) {
DL_ERR("missing PT_DYNAMIC in \"%s\"", si->name);
}
return false;
} else {
if (!relocating_linker) {
DEBUG("dynamic = %p", si->dynamic);
}
}
#if defined(__arm__)
(void) phdr_table_get_arm_exidx(phdr, phnum, base,
&si->ARM_exidx, &si->ARM_exidx_count);
#endif
// Extract useful information from dynamic section.
uint32_t needed_count = 0;
for (ElfW(Dyn)* d = si->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_HASH:
si->nbucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[0];
si->nchain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr)[1];
si->bucket = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8);
si->chain = reinterpret_cast<uint32_t*>(base + d->d_un.d_ptr + 8 + si->nbucket * 4);
break;
case DT_STRTAB:
si->strtab = reinterpret_cast<const char*>(base + d->d_un.d_ptr);
break;
case DT_SYMTAB:
si->symtab = reinterpret_cast<ElfW(Sym)*>(base + d->d_un.d_ptr);
break;
#if !defined(__LP64__)
case DT_PLTREL:
if (d->d_un.d_val != DT_REL) {
DL_ERR("unsupported DT_RELA in \"%s\"", si->name);
return false;
}
break;
#endif
case DT_JMPREL:
#if defined(USE_RELA)
si->plt_rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr);
#else
si->plt_rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr);
#endif
break;
case DT_PLTRELSZ:
#if defined(USE_RELA)
si->plt_rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
#else
si->plt_rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
#endif
break;
#if defined(__mips__)
case DT_PLTGOT:
// Used by mips and mips64.
si->plt_got = reinterpret_cast<ElfW(Addr)**>(base + d->d_un.d_ptr);
break;
#endif
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 containng 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);
}
break;
#endif
#if defined(USE_RELA)
case DT_RELA:
si->rela = reinterpret_cast<ElfW(Rela)*>(base + d->d_un.d_ptr);
break;
case DT_RELASZ:
si->rela_count = d->d_un.d_val / sizeof(ElfW(Rela));
break;
case DT_REL:
DL_ERR("unsupported DT_REL in \"%s\"", si->name);
return false;
case DT_RELSZ:
DL_ERR("unsupported DT_RELSZ in \"%s\"", si->name);
return false;
#else
case DT_REL:
si->rel = reinterpret_cast<ElfW(Rel)*>(base + d->d_un.d_ptr);
break;
case DT_RELSZ:
si->rel_count = d->d_un.d_val / sizeof(ElfW(Rel));
break;
case DT_RELA:
DL_ERR("unsupported DT_RELA in \"%s\"", si->name);
return false;
#endif
case DT_INIT:
si->init_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr);
DEBUG("%s constructors (DT_INIT) found at %p", si->name, si->init_func);
break;
case DT_FINI:
si->fini_func = reinterpret_cast<linker_function_t>(base + d->d_un.d_ptr);
DEBUG("%s destructors (DT_FINI) found at %p", si->name, si->fini_func);
break;
case DT_INIT_ARRAY:
si->init_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
DEBUG("%s constructors (DT_INIT_ARRAY) found at %p", si->name, si->init_array);
break;
case DT_INIT_ARRAYSZ:
si->init_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
break;
case DT_FINI_ARRAY:
si->fini_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
DEBUG("%s destructors (DT_FINI_ARRAY) found at %p", si->name, si->fini_array);
break;
case DT_FINI_ARRAYSZ:
si->fini_array_count = ((unsigned)d->d_un.d_val) / sizeof(ElfW(Addr));
break;
case DT_PREINIT_ARRAY:
si->preinit_array = reinterpret_cast<linker_function_t*>(base + d->d_un.d_ptr);
DEBUG("%s constructors (DT_PREINIT_ARRAY) found at %p", si->name, si->preinit_array);
break;
case DT_PREINIT_ARRAYSZ:
si->preinit_array_count = ((unsigned)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\"", si->name);
return false;
#else
si->has_text_relocations = true;
break;
#endif
case DT_SYMBOLIC:
si->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\"", si->name);
return false;
#else
si->has_text_relocations = true;
#endif
}
if (d->d_un.d_val & DF_SYMBOLIC) {
si->has_DT_SYMBOLIC = true;
}
break;
#if defined(__mips__)
case DT_STRSZ:
case DT_SYMENT:
case DT_RELENT:
break;
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**>(base + d->d_un.d_ptr);
*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:
si->mips_symtabno = d->d_un.d_val;
break;
case DT_MIPS_LOCAL_GOTNO:
si->mips_local_gotno = d->d_un.d_val;
break;
case DT_MIPS_GOTSYM:
si->mips_gotsym = d->d_un.d_val;
break;
#endif
default:
DEBUG("Unused DT entry: type %p arg %p",
reinterpret_cast<void*>(d->d_tag), reinterpret_cast<void*>(d->d_un.d_val));
break;
}
}
DEBUG("si->base = %p, si->strtab = %p, si->symtab = %p",
reinterpret_cast<void*>(si->base), si->strtab, si->symtab);
// Sanity checks.
if (relocating_linker && needed_count != 0) {
DL_ERR("linker cannot have DT_NEEDED dependencies on other libraries");
return false;
}
if (si->nbucket == 0) {
DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", si->name);
return false;
}
if (si->strtab == 0) {
DL_ERR("empty/missing DT_STRTAB in \"%s\"", si->name);
return false;
}
if (si->symtab == 0) {
DL_ERR("empty/missing DT_SYMTAB in \"%s\"", si->name);
return false;
}
// If this is the main executable, then load all of the libraries from LD_PRELOAD now.
if (si->flags & FLAG_EXE) {
memset(g_ld_preloads, 0, sizeof(g_ld_preloads));
size_t preload_count = 0;
for (size_t i = 0; g_ld_preload_names[i] != NULL; i++) {
soinfo* lsi = find_library(g_ld_preload_names[i], 0, NULL);
if (lsi != NULL) {
g_ld_preloads[preload_count++] = lsi;
} else {
// As with glibc, failure to load an LD_PRELOAD library is just a warning.
DL_WARN("could not load library \"%s\" from LD_PRELOAD for \"%s\"; caused by %s",
g_ld_preload_names[i], si->name, linker_get_error_buffer());
}
}
}
soinfo** needed = reinterpret_cast<soinfo**>(alloca((1 + needed_count) * sizeof(soinfo*)));
soinfo** pneeded = needed;
for (ElfW(Dyn)* d = si->dynamic; d->d_tag != DT_NULL; ++d) {
if (d->d_tag == DT_NEEDED) {
const char* library_name = si->strtab + d->d_un.d_val;
DEBUG("%s needs %s", si->name, library_name);
soinfo* lsi = find_library(library_name, 0, NULL);
if (lsi == NULL) {
strlcpy(tmp_err_buf, linker_get_error_buffer(), sizeof(tmp_err_buf));
DL_ERR("could not load library \"%s\" needed by \"%s\"; caused by %s",
library_name, si->name, tmp_err_buf);
return false;
}
si->add_child(lsi);
*pneeded++ = lsi;
}
}
*pneeded = NULL;
#if !defined(__LP64__)
if (si->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.
#if !defined(__i386__) // The platform itself has too many text relocations on x86.
DL_WARN("%s has text relocations. This is wasting memory and prevents "
"security hardening. Please fix.", si->name);
#endif
if (phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias) < 0) {
DL_ERR("can't unprotect loadable segments for \"%s\": %s",
si->name, strerror(errno));
return false;
}
}
#endif
#if defined(USE_RELA)
if (si->plt_rela != NULL) {
DEBUG("[ relocating %s plt ]\n", si->name);
if (soinfo_relocate(si, si->plt_rela, si->plt_rela_count, needed)) {
return false;
}
}
if (si->rela != NULL) {
DEBUG("[ relocating %s ]\n", si->name);
if (soinfo_relocate(si, si->rela, si->rela_count, needed)) {
return false;
}
}
#else
if (si->plt_rel != NULL) {
DEBUG("[ relocating %s plt ]", si->name);
if (soinfo_relocate(si, si->plt_rel, si->plt_rel_count, needed)) {
return false;
}
}
if (si->rel != NULL) {
DEBUG("[ relocating %s ]", si->name);
if (soinfo_relocate(si, si->rel, si->rel_count, needed)) {
return false;
}
}
#endif
#if defined(__mips__)
if (!mips_relocate_got(si, needed)) {
return false;
}
#endif
si->flags |= FLAG_LINKED;
DEBUG("[ finished linking %s ]", si->name);
#if !defined(__LP64__)
if (si->has_text_relocations) {
// All relocations are done, we can protect our segments back to read-only.
if (phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias) < 0) {
DL_ERR("can't protect segments for \"%s\": %s",
si->name, strerror(errno));
return false;
}
}
#endif
/* We can also turn on GNU RELRO protection */
if (phdr_table_protect_gnu_relro(si->phdr, si->phnum, si->load_bias) < 0) {
DL_ERR("can't enable GNU RELRO protection for \"%s\": %s",
si->name, strerror(errno));
return false;
}
/* Handle serializing/sharing the RELRO segment */
if (extinfo && (extinfo->flags & ANDROID_DLEXT_WRITE_RELRO)) {
if (phdr_table_serialize_gnu_relro(si->phdr, si->phnum, si->load_bias,
extinfo->relro_fd) < 0) {
DL_ERR("failed serializing GNU RELRO section for \"%s\": %s",
si->name, strerror(errno));
return false;
}
} else if (extinfo && (extinfo->flags & ANDROID_DLEXT_USE_RELRO)) {
if (phdr_table_map_gnu_relro(si->phdr, si->phnum, si->load_bias,
extinfo->relro_fd) < 0) {
DL_ERR("failed mapping GNU RELRO section for \"%s\": %s",
si->name, strerror(errno));
return false;
}
}
notify_gdb_of_load(si);
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 == NULL) {
return;
}
soinfo* si = soinfo_alloc("[vdso]", NULL);
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);
soinfo_link_image(si, NULL);
#endif
}
/*
* This is linker soinfo for GDB. See details below.
*/
static soinfo linker_soinfo_for_gdb;
/* 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) {
#if defined(__LP64__)
strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker64", sizeof(linker_soinfo_for_gdb.name));
#else
strlcpy(linker_soinfo_for_gdb.name, "/system/bin/linker", sizeof(linker_soinfo_for_gdb.name));
#endif
linker_soinfo_for_gdb.flags = FLAG_NEW_SOINFO;
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, NULL, NULL);
insert_soinfo_into_debug_map(&linker_soinfo_for_gdb);
}
/*
* 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) {
/* NOTE: we store the args pointer on a special location
* of the temporary TLS area in order to pass it to
* the C Library's runtime initializer.
*
* The initializer must clear the slot and reset the TLS
* to point to a different location to ensure that no other
* shared library constructor can access it.
*/
__libc_init_tls(args);
#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);
// 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 != NULL) {
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 = NULL;
const char* ldpreload_env = NULL;
if (!get_AT_SECURE()) {
ldpath_env = linker_env_get("LD_LIBRARY_PATH");
ldpreload_env = linker_env_get("LD_PRELOAD");
}
// Linker does not call constructors for its own
// global variables so we need to initialize
// the allocators explicitly.
g_soinfo_allocator.init();
g_soinfo_links_allocator.init();
INFO("[ android linker & debugger ]");
soinfo* si = soinfo_alloc(args.argv[0], NULL);
if (si == NULL) {
exit(EXIT_FAILURE);
}
/* bootstrap the link map, the main exe always needs to be first */
si->flags |= FLAG_EXE;
link_map* map = &(si->link_map_head);
map->l_addr = 0;
map->l_name = args.argv[0];
map->l_prev = NULL;
map->l_next = NULL;
_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 = NULL;
si->ref_count = 1;
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 (!soinfo_link_image(si, NULL)) {
__libc_format_fd(2, "CANNOT LINK EXECUTABLE: %s\n", linker_get_error_buffer());
exit(EXIT_FAILURE);
}
add_vdso(args);
si->CallPreInitConstructors();
for (size_t i = 0; g_ld_preloads[i] != NULL; ++i) {
g_ld_preloads[i]->CallConstructors();
}
/* After the link_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->CallConstructors();
#if TIMING
gettimeofday(&t1, NULL);
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->name, 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;
}
/*
* 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) {
// Initialize static variables.
solist = get_libdl_info();
sonext = get_libdl_info();
KernelArgumentBlock args(raw_args);
ElfW(Addr) linker_addr = args.getauxval(AT_BASE);
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;
memset(&linker_so, 0, sizeof(soinfo));
strcpy(linker_so.name, "[dynamic linker]");
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 = NULL;
linker_so.phdr = phdr;
linker_so.phnum = elf_hdr->e_phnum;
linker_so.flags |= FLAG_LINKER;
if (!soinfo_link_image(&linker_so, NULL)) {
// 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);
}
// 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);
protect_data(PROT_READ);
// Return the address that the calling assembly stub should jump to.
return start_address;
}
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