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Add support for hash-style=gnu

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Change-Id: I171434a587420895feac8a9b1ad2342087197568
This commit is contained in:
Dmitriy Ivanov 2014-11-09 19:27:20 -08:00
parent e5cabca516
commit ec18ce06f2
6 changed files with 241 additions and 68 deletions
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3
libc/include/elf.h
View File

@ -94,6 +94,9 @@ typedef struct {
#define DT_PREINIT_ARRAY 32
#define DT_PREINIT_ARRAYSZ 33
/* gnu hash entry */
#define DT_GNU_HASH 0x6ffffef5
#define ELFOSABI_SYSV 0 /* Synonym for ELFOSABI_NONE used by valgrind. */
#define PT_GNU_RELRO 0x6474e552

2
linker/dlfcn.cpp
View File

@ -145,7 +145,7 @@ int dladdr(const void* addr, Dl_info* info) {
info->dli_fbase = reinterpret_cast<void*>(si->base);
// Determine if any symbol in the library contains the specified address.
ElfW(Sym)* sym = dladdr_find_symbol(si, addr);
ElfW(Sym)* sym = si->find_symbol_by_address(addr);
if (sym != nullptr) {
info->dli_sname = si->get_string(sym->st_name);
info->dli_saddr = reinterpret_cast<void*>(si->resolve_symbol_address(sym));

221
linker/linker.cpp
View File

@ -35,6 +35,7 @@
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <unistd.h>
#include <new>
@ -316,6 +317,7 @@ static void soinfo_free(soinfo* si) {
}
prev = trav;
}
if (trav == nullptr) {
// si was not in solist
DL_ERR("name \"%s\" is not in solist!", si->name);
@ -335,7 +337,6 @@ static void soinfo_free(soinfo* si) {
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 == nullptr) {
@ -415,39 +416,72 @@ int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void
return rv;
}
static ElfW(Sym)* soinfo_elf_lookup(const soinfo* si, unsigned hash, const char* name) {
ElfW(Sym)* symtab = si->symtab;
ElfW(Sym)* soinfo::find_symbol_by_name(SymbolName& symbol_name) {
return is_gnu_hash() ? gnu_lookup(symbol_name) : elf_lookup(symbol_name);
}
TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p %x %zd",
name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
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->name);
}
for (unsigned n = si->bucket[hash % si->nbucket]; n != 0; n = si->chain[n]) {
return false;
}
ElfW(Sym)* soinfo::gnu_lookup(SymbolName& symbol_name) {
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];
// test against bloom filter
if ((1 & (bloom_word >> (hash % bloom_mask_bits)) & (bloom_word >> (h2 % bloom_mask_bits))) == 0) {
return nullptr;
}
// bloom test says "probably yes"...
uint32_t n = bucket[hash % nbucket];
if (n == 0) {
return nullptr;
}
do {
ElfW(Sym)* s = symtab + n;
if (strcmp(si->get_string(s->st_name), name)) continue;
if (((chain[n] ^ hash) >> 1) == 0 &&
strcmp(get_string(s->st_name), symbol_name.get_name()) == 0 &&
is_symbol_global_and_defined(this, s)) {
return s;
}
} while ((chain[n++] & 1) == 0);
// 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;
}
return nullptr;
}
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;
case STB_LOCAL:
continue;
default:
__libc_fatal("ERROR: Unexpected ST_BIND value: %d for '%s' in '%s'",
ELF_ST_BIND(s->st_info), name, si->name);
ElfW(Sym)* soinfo::elf_lookup(SymbolName& symbol_name) {
uint32_t hash = symbol_name.elf_hash();
TRACE_TYPE(LOOKUP, "SEARCH %s in %s@%p h=%x(elf) %zd",
symbol_name.get_name(), name, reinterpret_cast<void*>(base), hash, hash % nbucket);
for (uint32_t n = bucket[hash % nbucket]; n != 0; n = chain[n]) {
ElfW(Sym)* s = symtab + n;
if (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(), name, reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
return s;
}
}
TRACE_TYPE(LOOKUP, "NOT FOUND %s in %s@%p %x %zd",
name, si->name, reinterpret_cast<void*>(si->base), hash, hash % si->nbucket);
symbol_name.get_name(), name, reinterpret_cast<void*>(base), hash, hash % nbucket);
return nullptr;
}
@ -468,22 +502,44 @@ soinfo::soinfo(const char* name, const struct stat* file_stat, off64_t file_offs
this->rtld_flags = rtld_flags;
}
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;
uint32_t SymbolName::elf_hash() {
if (!has_elf_hash_) {
const unsigned char* name = reinterpret_cast<const unsigned char*>(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 h;
return elf_hash_;
}
uint32_t SymbolName::gnu_hash() {
if (!has_gnu_hash_) {
uint32_t h = 5381;
const unsigned char* name = reinterpret_cast<const unsigned char*>(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_;
}
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);
SymbolName symbol_name(name);
ElfW(Sym)* s = nullptr;
/* "This element's presence in a shared object library alters the dynamic linker's
@ -499,7 +555,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** s
*/
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);
s = si_from->find_symbol_by_name(symbol_name);
if (s != nullptr) {
*si_found_in = si_from;
}
@ -509,7 +565,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** s
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);
s = global_si->find_symbol_by_name(symbol_name);
if (s != nullptr) {
*si_found_in = global_si;
return false;
@ -528,7 +584,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si_from, const char* name, soinfo** s
}
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);
s = local_si->find_symbol_by_name(symbol_name);
if (s != nullptr) {
*si_found_in = local_si;
return false;
@ -665,11 +721,11 @@ static bool walk_dependencies_tree(soinfo* root_soinfos[], size_t root_soinfos_s
// specified soinfo object and its dependencies in breadth first order.
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
ElfW(Sym)* result = nullptr;
uint32_t elf_hash = elfhash(name);
SymbolName symbol_name(name);
walk_dependencies_tree(&si, 1, [&](soinfo* current_soinfo) {
result = soinfo_elf_lookup(current_soinfo, elf_hash, name);
result = current_soinfo->find_symbol_by_name(symbol_name);
if (result != nullptr) {
*found = current_soinfo;
return false;
@ -687,7 +743,7 @@ ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name) {
specified soinfo (for RTLD_NEXT).
*/
ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
unsigned elf_hash = elfhash(name);
SymbolName symbol_name(name);
if (start == nullptr) {
start = solist;
@ -699,7 +755,7 @@ ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start)
continue;
}
s = soinfo_elf_lookup(si, elf_hash, name);
s = si->find_symbol_by_name(symbol_name);
if (s != nullptr) {
*found = si;
break;
@ -724,16 +780,45 @@ soinfo* find_containing_library(const void* p) {
return nullptr;
}
ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr) {
ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - si->base;
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) - base;
for (size_t i = 0; i < nbucket; ++i) {
uint32_t n = bucket[i];
if (n == 0) {
continue;
}
do {
ElfW(Sym)* sym = symtab + n;
if (symbol_matches_soaddr(sym, soaddr)) {
return sym;
}
} while ((chain[n++] & 1) == 0);
}
return nullptr;
}
ElfW(Sym)* soinfo::elf_addr_lookup(const void* addr) {
ElfW(Addr) soaddr = reinterpret_cast<ElfW(Addr)>(addr) - 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) {
for (size_t i = 0; i < nchain; ++i) {
ElfW(Sym)* sym = symtab + i;
if (symbol_matches_soaddr(sym, soaddr)) {
return sym;
}
}
@ -1898,6 +1983,10 @@ const char* soinfo::get_string(ElfW(Word) index) const {
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;
}
@ -2003,12 +2092,42 @@ bool soinfo::PrelinkImage() {
break;
case DT_HASH:
if (nbucket != 0) {
// in case of --hash-style=both, we prefer gnu
break;
}
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:
if (nbucket != 0) {
// in case of --hash-style=both, we prefer gnu
nchain = 0;
}
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);
bucket = reinterpret_cast<uint32_t*>(gnu_bloom_filter + gnu_maskwords);
// amend chain for symndx = header[1]
chain = bucket + 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, name);
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;
@ -2023,7 +2142,7 @@ bool soinfo::PrelinkImage() {
case DT_SYMENT:
if (d->d_un.d_val != sizeof(ElfW(Sym))) {
DL_ERR("invalid DT_SYMENT: %zd", static_cast<size_t>(d->d_un.d_val));
DL_ERR("invalid DT_SYMENT: %zd in \"%s\"", static_cast<size_t>(d->d_un.d_val), name);
return false;
}
break;
@ -2263,7 +2382,7 @@ bool soinfo::PrelinkImage() {
return false;
}
if (nbucket == 0) {
DL_ERR("empty/missing DT_HASH in \"%s\" (built with --hash-style=gnu?)", name);
DL_ERR("empty/missing DT_HASH/DT_GNU_HASH in \"%s\" (new hash type from the future?)", name);
return false;
}
if (strtab == 0) {

46
linker/linker.h
View File

@ -87,6 +87,7 @@
#define FLAG_LINKED 0x00000001
#define FLAG_EXE 0x00000004 // The main executable
#define FLAG_LINKER 0x00000010 // The linker itself
#define FLAG_GNU_HASH 0x00000040 // uses gnu hash
#define FLAG_NEW_SOINFO 0x40000000 // new soinfo format
#define SUPPORTED_DT_FLAGS_1 (DF_1_NOW | DF_1_GLOBAL | DF_1_NODELETE)
@ -105,14 +106,38 @@ typedef void (*linker_function_t)();
struct soinfo;
class SoinfoListAllocator {
public:
public:
static LinkedListEntry<soinfo>* alloc();
static void free(LinkedListEntry<soinfo>* entry);
private:
private:
// unconstructable
DISALLOW_IMPLICIT_CONSTRUCTORS(SoinfoListAllocator);
};
class SymbolName {
public:
explicit SymbolName(const char* name)
: name_(name), has_elf_hash_(false), has_gnu_hash_(false),
elf_hash_(0), gnu_hash_(0) { }
const char* get_name() {
return name_;
}
uint32_t elf_hash();
uint32_t gnu_hash();
private:
const char* name_;
bool has_elf_hash_;
bool has_gnu_hash_;
uint32_t elf_hash_;
uint32_t gnu_hash_;
DISALLOW_IMPLICIT_CONSTRUCTORS(SymbolName);
};
struct soinfo {
public:
typedef LinkedList<soinfo, SoinfoListAllocator> soinfo_list_t;
@ -140,7 +165,6 @@ struct soinfo {
private:
const char* strtab;
public:
ElfW(Sym)* symtab;
size_t nbucket;
@ -148,6 +172,7 @@ struct soinfo {
uint32_t* bucket;
uint32_t* chain;
public:
#if defined(__mips__) || !defined(__LP64__)
// This is only used by mips and mips64, but needs to be here for
// all 32-bit architectures to preserve binary compatibility.
@ -225,16 +250,24 @@ struct soinfo {
soinfo_list_t& get_children();
soinfo_list_t& get_parents();
ElfW(Sym)* find_symbol_by_name(SymbolName& symbol_name);
ElfW(Sym)* find_symbol_by_address(const void* addr);
ElfW(Addr) resolve_symbol_address(ElfW(Sym)* s);
const char* get_string(ElfW(Word) index) const;
bool can_unload() const;
bool is_gnu_hash() const;
bool inline has_min_version(uint32_t min_version) const {
return (flags & FLAG_NEW_SOINFO) != 0 && version >= min_version;
}
private:
ElfW(Sym)* elf_lookup(SymbolName& symbol_name);
ElfW(Sym)* elf_addr_lookup(const void* addr);
ElfW(Sym)* gnu_lookup(SymbolName& symbol_name);
ElfW(Sym)* gnu_addr_lookup(const void* addr);
void CallArray(const char* array_name, linker_function_t* functions, size_t count, bool reverse);
void CallFunction(const char* function_name, linker_function_t function);
#if defined(USE_RELA)
@ -262,6 +295,12 @@ struct soinfo {
uint32_t dt_flags_1;
size_t strtab_size;
// version >= 2
uint32_t gnu_maskwords;
uint32_t gnu_shift2;
ElfW(Addr)* gnu_bloom_filter;
friend soinfo* get_libdl_info();
};
@ -275,7 +314,6 @@ void do_dlclose(soinfo* si);
ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start);
soinfo* find_containing_library(const void* addr);
ElfW(Sym)* dladdr_find_symbol(soinfo* si, const void* addr);
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, soinfo** found, const char* name);
void debuggerd_init();

29
tests/dlfcn_test.cpp
View File

@ -648,19 +648,32 @@ TEST(dlfcn, dladdr_invalid) {
ASSERT_TRUE(dlerror() == NULL); // dladdr(3) doesn't set dlerror(3).
}
// Our dynamic linker doesn't support GNU hash tables.
#if defined(__BIONIC__)
// GNU-style ELF hash tables are incompatible with the MIPS ABI.
// MIPS requires .dynsym to be sorted to match the GOT but GNU-style requires sorting by hash code.
#if !defined(__mips__)
TEST(dlfcn, dlopen_library_with_only_gnu_hash) {
#if !defined(__mips__)
dlerror(); // Clear any pending errors.
void* handle = dlopen("no-elf-hash-table-library.so", RTLD_NOW);
ASSERT_TRUE(handle == NULL);
ASSERT_STREQ("dlopen failed: empty/missing DT_HASH in \"no-elf-hash-table-library.so\" (built with --hash-style=gnu?)", dlerror());
void* handle = dlopen("libgnu-hash-table-library.so", RTLD_NOW);
ASSERT_TRUE(handle != nullptr) << dlerror();
auto guard = make_scope_guard([&]() {
dlclose(handle);
});
void* sym = dlsym(handle, "getRandomNumber");
ASSERT_TRUE(sym != nullptr) << dlerror();
int (*fn)(void);
fn = reinterpret_cast<int (*)(void)>(sym);
EXPECT_EQ(4, fn());
Dl_info dlinfo;
ASSERT_TRUE(0 != dladdr(reinterpret_cast<void*>(fn), &dlinfo));
ASSERT_TRUE(fn == dlinfo.dli_saddr);
ASSERT_STREQ("getRandomNumber", dlinfo.dli_sname);
ASSERT_STREQ("libgnu-hash-table-library.so", dlinfo.dli_fname);
#else
GTEST_LOG_(INFO) << "This test does nothing for mips/mips64; mips toolchain does not support '--hash-style=gnu'\n";
#endif
}
#endif
#endif
TEST(dlfcn, dlopen_bad_flags) {
dlerror(); // Clear any pending errors.

8
tests/libs/Android.mk
View File

@ -31,13 +31,13 @@ common_additional_dependencies := \
# Library used by dlfcn tests.
# -----------------------------------------------------------------------------
ifneq ($(TARGET_ARCH),$(filter $(TARGET_ARCH),mips mips64))
no-elf-hash-table-library_src_files := \
empty.cpp \
libgnu-hash-table-library_src_files := \
dlext_test_library.cpp \
no-elf-hash-table-library_ldflags := \
libgnu-hash-table-library_ldflags := \
-Wl,--hash-style=gnu \
module := no-elf-hash-table-library
module := libgnu-hash-table-library
module_tag := optional
include $(LOCAL_PATH)/Android.build.testlib.mk
endif