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Fix symbol lookup order during relocation

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Relocate symbol against DF_1_GLOBAL shared libraries
  loaded before this shared library. This includes
  main executable, ld_preloads and other libraries
  that have DF_1_GLOBAL flag set.

Bug: 2643900
Bug: 15432753
Change-Id: Ia788748be59b739d1c7e62b978e7e255f9e65c7b
This commit is contained in:
Dmitriy Ivanov
2014-08-28 14:12:12 -07:00
parent d50495a567
commit d225a5e652
11 changed files with 384 additions and 70 deletions
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162
linker/linker.cpp
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@@ -282,7 +282,7 @@ static void protect_data(int protection) {
g_soinfo_links_allocator.protect_all(protection);
}
static soinfo* soinfo_alloc(const char* name, struct stat* file_stat, off64_t file_offset, int rtld_flags) {
static soinfo* soinfo_alloc(const char* name, struct stat* file_stat, off64_t file_offset, uint32_t rtld_flags) {
if (strlen(name) >= SOINFO_NAME_LEN) {
DL_ERR("library name \"%s\" too long", name);
return nullptr;
@@ -481,7 +481,8 @@ static unsigned elfhash(const char* _name) {
return h;
}
static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, const soinfo::soinfo_list_t& local_group) {
static ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** si_found_in,
const soinfo::soinfo_list_t& global_group, const soinfo::soinfo_list_t& local_group) {
unsigned elf_hash = elfhash(name);
ElfW(Sym)* s = nullptr;
@@ -496,49 +497,40 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, c
* Note that this is unlikely since static linker avoids generating
* relocations for -Bsymbolic linked dynamic executables.
*/
if (si->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si->name, name);
s = soinfo_elf_lookup(si, elf_hash, name);
if (si_from->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in local scope (DT_SYMBOLIC)", si_from->name, name);
s = soinfo_elf_lookup(si_from, elf_hash, name);
if (s != nullptr) {
*lsi = si;
*si_found_in = si_from;
}
}
if (s == nullptr && somain != nullptr) {
// 1. Look for it in the main executable unless we already did.
if (si != somain || !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);
// 1. Look for it in global_group
if (s == nullptr) {
global_group.visit([&](soinfo* global_si) {
DEBUG("%s: looking up %s in %s (from global group)", si_from->name, name, global_si->name);
s = soinfo_elf_lookup(global_si, elf_hash, name);
if (s != nullptr) {
*lsi = somain;
*si_found_in = global_si;
return false;
}
}
// 2. Look for it in the ld_preloads
if (s == nullptr) {
for (int i = 0; g_ld_preloads[i] != NULL; i++) {
s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
if (s != nullptr) {
*lsi = g_ld_preloads[i];
break;
}
}
}
return true;
});
}
// 3. Look for it in the local group
// 2. Look for it in the local group
if (s == nullptr) {
local_group.visit([&](soinfo* local_si) {
if (local_si == si && si->has_DT_SYMBOLIC) {
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->name, name, local_si->name);
DEBUG("%s: looking up %s in %s (from local group)", si_from->name, name, local_si->name);
s = soinfo_elf_lookup(local_si, elf_hash, name);
if (s != nullptr) {
*lsi = local_si;
*si_found_in = local_si;
return false;
}
@@ -549,9 +541,9 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, c
if (s != nullptr) {
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));
si_from->name, name, reinterpret_cast<void*>(s->st_value),
(*si_found_in)->name, reinterpret_cast<void*>((*si_found_in)->base),
reinterpret_cast<void*>((*si_found_in)->load_bias));
}
return s;
@@ -916,6 +908,24 @@ static bool is_recursive(soinfo* si, soinfo* parent) {
});
}
// 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[],
soinfo* ld_preloads[], size_t ld_preloads_count, int rtld_flags, const android_dlextinfo* extinfo) {
// Step 0: prepare.
@@ -925,6 +935,9 @@ static bool find_libraries(soinfo* start_with, const char* const library_names[]
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
@@ -973,6 +986,11 @@ static bool find_libraries(soinfo* start_with, const char* const library_names[]
// 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[soinfos_count] = si;
}
@@ -993,7 +1011,7 @@ static bool find_libraries(soinfo* start_with, const char* const library_names[]
bool linked = local_group.visit([&](soinfo* si) {
if ((si->flags & FLAG_LINKED) == 0) {
if (!si->LinkImage(local_group, extinfo)) {
if (!si->LinkImage(global_group, local_group, extinfo)) {
return false;
}
si->flags |= FLAG_LINKED;
@@ -1128,7 +1146,7 @@ static ElfW(Addr) call_ifunc_resolver(ElfW(Addr) resolver_addr) {
}
#if defined(USE_RELA)
int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& local_group) {
int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& global_group, const soinfo_list_t& local_group) {
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);
@@ -1146,7 +1164,7 @@ int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& loca
if (sym != 0) {
sym_name = get_string(symtab[sym].st_name);
s = soinfo_do_lookup(this, sym_name, &lsi, local_group);
s = soinfo_do_lookup(this, sym_name, &lsi, global_group,local_group);
if (s == nullptr) {
// We only allow an undefined symbol if this is a weak reference...
s = &symtab[sym];
@@ -1405,7 +1423,7 @@ int soinfo::Relocate(ElfW(Rela)* rela, unsigned count, const soinfo_list_t& loca
}
#else // REL, not RELA.
int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& local_group) {
int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& global_group, const soinfo_list_t& local_group) {
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.
@@ -1424,7 +1442,7 @@ int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& local_
if (sym != 0) {
sym_name = get_string(symtab[sym].st_name);
s = soinfo_do_lookup(this, sym_name, &lsi, local_group);
s = soinfo_do_lookup(this, sym_name, &lsi, global_group, local_group);
if (s == nullptr) {
// We only allow an undefined symbol if this is a weak reference...
s = &symtab[sym];
@@ -1610,7 +1628,7 @@ int soinfo::Relocate(ElfW(Rel)* rel, unsigned count, const soinfo_list_t& local_
#endif
#if defined(__mips__)
static bool mips_relocate_got(soinfo* si, const soinfo::soinfo_list_t& local_group) {
static bool mips_relocate_got(soinfo* si, const soinfo::soinfo_list_t& global_group, const soinfo::soinfo_list_t& local_group) {
ElfW(Addr)** got = si->plt_got;
if (got == nullptr) {
return true;
@@ -1643,7 +1661,7 @@ static bool mips_relocate_got(soinfo* si, const soinfo::soinfo_list_t& local_gro
// This is an undefined reference... try to locate it.
const char* sym_name = si->get_string(sym->st_name);
soinfo* lsi = nullptr;
ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, local_group);
ElfW(Sym)* s = soinfo_do_lookup(si, sym_name, &lsi, global_group, local_group);
if (s == nullptr) {
// We only allow an undefined symbol if this is a weak reference.
s = &symtab[g];
@@ -1783,7 +1801,7 @@ void soinfo::remove_all_links() {
children.clear();
}
dev_t soinfo::get_st_dev() {
dev_t soinfo::get_st_dev() const {
if (has_min_version(0)) {
return st_dev;
}
@@ -1791,7 +1809,7 @@ dev_t soinfo::get_st_dev() {
return 0;
};
ino_t soinfo::get_st_ino() {
ino_t soinfo::get_st_ino() const {
if (has_min_version(0)) {
return st_ino;
}
@@ -1799,7 +1817,7 @@ ino_t soinfo::get_st_ino() {
return 0;
}
off64_t soinfo::get_file_offset() {
off64_t soinfo::get_file_offset() const {
if (has_min_version(1)) {
return file_offset;
}
@@ -1807,7 +1825,7 @@ off64_t soinfo::get_file_offset() {
return 0;
}
int soinfo::get_rtld_flags() {
uint32_t soinfo::get_rtld_flags() const {
if (has_min_version(1)) {
return rtld_flags;
}
@@ -1815,6 +1833,27 @@ int soinfo::get_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;
}
this->dt_flags_1 = dt_flags_1;
}
}
// 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;
@@ -1852,8 +1891,9 @@ const char* soinfo::get_string(ElfW(Word) index) const {
}
bool soinfo::can_unload() const {
return (rtld_flags & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
return (get_rtld_flags() & (RTLD_NODELETE | RTLD_GLOBAL)) == 0;
}
/* Force any of the closed stdin, stdout and stderr to be associated with
/dev/null. */
static int nullify_closed_stdio() {
@@ -2154,16 +2194,9 @@ bool soinfo::PrelinkImage() {
break;
case DT_FLAGS_1:
if ((d->d_un.d_val & DF_1_GLOBAL) != 0) {
rtld_flags |= RTLD_GLOBAL;
}
set_dt_flags_1(d->d_un.d_val);
if ((d->d_un.d_val & DF_1_NODELETE) != 0) {
rtld_flags |= RTLD_NODELETE;
}
// TODO: Implement other flags
if ((d->d_un.d_val & ~(DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE)) != 0) {
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;
@@ -2236,7 +2269,7 @@ bool soinfo::PrelinkImage() {
return true;
}
bool soinfo::LinkImage(const soinfo_list_t& local_group, const android_dlextinfo* extinfo) {
bool soinfo::LinkImage(const soinfo_list_t& global_group, const soinfo_list_t& local_group, const android_dlextinfo* extinfo) {
#if !defined(__LP64__)
if (has_text_relocations) {
@@ -2255,33 +2288,33 @@ bool soinfo::LinkImage(const soinfo_list_t& local_group, const android_dlextinfo
#if defined(USE_RELA)
if (rela != nullptr) {
DEBUG("[ relocating %s ]", name);
if (Relocate(rela, rela_count, local_group)) {
if (Relocate(rela, rela_count, global_group, local_group)) {
return false;
}
}
if (plt_rela != nullptr) {
DEBUG("[ relocating %s plt ]", name);
if (Relocate(plt_rela, plt_rela_count, local_group)) {
if (Relocate(plt_rela, plt_rela_count, global_group, local_group)) {
return false;
}
}
#else
if (rel != nullptr) {
DEBUG("[ relocating %s ]", name);
if (Relocate(rel, rel_count, local_group)) {
if (Relocate(rel, rel_count, global_group, local_group)) {
return false;
}
}
if (plt_rel != nullptr) {
DEBUG("[ relocating %s plt ]", name);
if (Relocate(plt_rel, plt_rel_count, local_group)) {
if (Relocate(plt_rel, plt_rel_count, global_group, local_group)) {
return false;
}
}
#endif
#if defined(__mips__)
if (!mips_relocate_got(this, local_group)) {
if (!mips_relocate_got(this, global_group, local_group)) {
return false;
}
#endif
@@ -2348,7 +2381,7 @@ static void add_vdso(KernelArgumentBlock& args __unused) {
si->load_bias = get_elf_exec_load_bias(ehdr_vdso);
si->PrelinkImage();
si->LinkImage(g_empty_list, nullptr);
si->LinkImage(g_empty_list, soinfo::soinfo_list_t::make_list(si), nullptr);
#endif
}
@@ -2479,6 +2512,9 @@ static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(
si->PrelinkImage();
// 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;
@@ -2622,7 +2658,13 @@ extern "C" ElfW(Addr) __linker_init(void* raw_args) {
linker_so.phnum = elf_hdr->e_phnum;
linker_so.flags |= FLAG_LINKER;
if (!(linker_so.PrelinkImage() && linker_so.LinkImage(g_empty_list, nullptr))) {
// 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.PrelinkImage() && linker_so.LinkImage(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