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linker: add dlvsym(3)

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This changes implements dlvsym - dlsym for versioned symbols.

Bug: http://b/22865643
Change-Id: Ic90a60d512104261a1416c43f9100f0d88e3b46f
This commit is contained in:
Dimitry Ivanov 2015-12-11 14:22:24 -08:00
parent d3e5301a75
commit 9cf99cbad8
12 changed files with 67 additions and 27 deletions
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11
libc/include/dlfcn.h
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@ -43,11 +43,12 @@ typedef struct {
in dli_sname */
} Dl_info;
extern void* dlopen(const char* filename, int flag);
extern int dlclose(void* handle);
extern const char* dlerror(void);
extern void* dlsym(void* handle, const char* symbol);
extern int dladdr(const void* addr, Dl_info *info);
extern void* dlopen(const char* filename, int flag);
extern int dlclose(void* handle);
extern const char* dlerror(void);
extern void* dlsym(void* handle, const char* symbol) __nonnull((2));
extern void* dlvsym(void* handle, const char* symbol, const char* version) __nonnull((2, 3));
extern int dladdr(const void* addr, Dl_info *info);
enum {
#if defined(__LP64__)

1
libdl/libdl.arm.map
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@ -18,6 +18,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

1
libdl/libdl.arm64.map
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@ -17,6 +17,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

8
libdl/libdl.c
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@ -24,9 +24,17 @@
// in the dynamic linker and hijacked at runtime.
void* dlopen(const char* filename __unused, int flag __unused) { return 0; }
const char* dlerror(void) { return 0; }
void* dlsym(void* handle __unused, const char* symbol __unused) { return 0; }
void* dlvsym(void* handle __unused, const char* symbol __unused, const char* version __unused) {
return 0;
}
int dladdr(const void* addr __unused, Dl_info* info __unused) { return 0; }
int dlclose(void* handle __unused) { return 0; }
#if defined(__arm__)

1
libdl/libdl.map.txt
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@ -32,6 +32,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

1
libdl/libdl.mips.map
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@ -17,6 +17,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

1
libdl/libdl.mips64.map
View File

@ -17,6 +17,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

1
libdl/libdl.x86.map
View File

@ -17,6 +17,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

1
libdl/libdl.x86_64.map
View File

@ -17,6 +17,7 @@ LIBC_N {
global:
android_init_namespaces;
android_create_namespace;
dlvsym;
} LIBC;
LIBC_PRIVATE {

30
linker/dlfcn.cpp
View File

@ -88,11 +88,10 @@ void* dlopen(const char* filename, int flags) {
extern android_namespace_t* g_anonymous_namespace;
void* dlsym(void* handle, const char* symbol) {
void* caller_addr = __builtin_return_address(0);
void* dlsym_impl(void* handle, const char* symbol, const char* version, void* caller_addr) {
ScopedPthreadMutexLocker locker(&g_dl_mutex);
void* result;
if (!do_dlsym(handle, symbol, nullptr, caller_addr, &result)) {
if (!do_dlsym(handle, symbol, version, caller_addr, &result)) {
__bionic_format_dlerror(linker_get_error_buffer(), nullptr);
return nullptr;
}
@ -100,6 +99,16 @@ void* dlsym(void* handle, const char* symbol) {
return result;
}
void* dlsym(void* handle, const char* symbol) {
void* caller_addr = __builtin_return_address(0);
return dlsym_impl(handle, symbol, nullptr, caller_addr);
}
void* dlvsym(void* handle, const char* symbol, const char* version) {
void* caller_addr = __builtin_return_address(0);
return dlsym_impl(handle, symbol, version, caller_addr);
}
int dladdr(const void* addr, Dl_info* info) {
ScopedPthreadMutexLocker locker(&g_dl_mutex);
return do_dladdr(addr, info);
@ -179,11 +188,11 @@ static const char ANDROID_LIBDL_STRTAB[] =
// 00000000001 1111111112222222222 3333333333444444444455555555556666666666777 777777788888888889999999999
// 01234567890 1234567890123456789 0123456789012345678901234567890123456789012 345678901234567890123456789
"erate_phdr\0android_dlopen_ext\0android_set_application_target_sdk_version\0android_get_application_tar"
// 0000000000111111 111122222222223333333333 4444444444555555555566666
// 0123456789012345 678901234567890123456789 0123456789012345678901234
"get_sdk_version\0android_init_namespaces\0android_create_namespace\0"
// 0000000000111111 111122222222223333333333 4444444444555555555566666 6666677
// 0123456789012345 678901234567890123456789 0123456789012345678901234 5678901
"get_sdk_version\0android_init_namespaces\0android_create_namespace\0dlvsym\0"
#if defined(__arm__)
// 265
// 272
"dl_unwind_find_exidx\0"
#endif
;
@ -207,8 +216,9 @@ static ElfW(Sym) g_libdl_symtab[] = {
ELFW(SYM_INITIALIZER)(173, &android_get_application_target_sdk_version, 1),
ELFW(SYM_INITIALIZER)(216, &android_init_namespaces, 1),
ELFW(SYM_INITIALIZER)(240, &android_create_namespace, 1),
ELFW(SYM_INITIALIZER)(265, &dlvsym, 1),
#if defined(__arm__)
ELFW(SYM_INITIALIZER)(265, &dl_unwind_find_exidx, 1),
ELFW(SYM_INITIALIZER)(272, &dl_unwind_find_exidx, 1),
#endif
};
@ -225,9 +235,9 @@ static ElfW(Sym) g_libdl_symtab[] = {
// Note that adding any new symbols here requires stubbing them out in libdl.
static unsigned g_libdl_buckets[1] = { 1 };
#if defined(__arm__)
static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 0 };
static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 0 };
#else
static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 0 };
static unsigned g_libdl_chains[] = { 0, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 0 };
#endif
static uint8_t __libdl_info_buf[sizeof(soinfo)] __attribute__((aligned(8)));

6
linker/linker.cpp
View File

@ -2187,7 +2187,7 @@ static std::string symbol_display_name(const char* sym_name, const char* sym_ver
return sym_name;
}
return std::string(sym_name) + "@" + sym_ver;
return std::string(sym_name) + ", version " + sym_ver;
}
void do_android_get_LD_LIBRARY_PATH(char* buffer, size_t buffer_size) {
@ -2312,8 +2312,8 @@ bool do_dlsym(void* handle, const char* sym_name, const char* sym_ver,
version_info* vi = nullptr;
if (sym_ver != nullptr) {
vi_instance.name = sym_name;
vi_instance.elf_hash = calculate_elf_hash(sym_name);
vi_instance.name = sym_ver;
vi_instance.elf_hash = calculate_elf_hash(sym_ver);
vi = &vi_instance;
}

32
tests/dlfcn_test.cpp
View File

@ -624,8 +624,10 @@ TEST(dlfcn, dlopen_check_loop) {
handle = dlopen("libtest_with_dependency_loop.so", RTLD_NOW | RTLD_NOLOAD);
ASSERT_TRUE(handle == nullptr);
#ifdef __BIONIC__
// TODO: glibc returns nullptr on dlerror() here. Is it bug?
ASSERT_STREQ("dlopen failed: library \"libtest_with_dependency_loop.so\" wasn't loaded and RTLD_NOLOAD prevented it", dlerror());
#else
// TODO: glibc returns nullptr on dlerror() here. Is it bug?
ASSERT_TRUE(dlerror() == nullptr);
#endif
handle = dlopen("libtest_with_dependency_a.so", RTLD_NOW | RTLD_NOLOAD);
@ -763,14 +765,6 @@ TEST(dlfcn, dlsym_failures) {
ASSERT_STREQ("dlsym failed: library handle is null", dlerror());
#endif
// NULL symbol name.
#if defined(__BIONIC__)
// glibc marks this parameter non-null and SEGVs if you cheat.
sym = dlsym(self, nullptr);
ASSERT_TRUE(sym == nullptr);
ASSERT_STREQ("dlsym failed: symbol name is null", dlerror());
#endif
// Symbol that doesn't exist.
sym = dlsym(self, "ThisSymbolDoesNotExist");
ASSERT_TRUE(sym == nullptr);
@ -1054,6 +1048,26 @@ TEST(dlfcn, symbol_versioning_default_via_dlsym) {
dlclose(handle);
}
TEST(dlfcn, dlvsym_smoke) {
void* handle = dlopen("libtest_versioned_lib.so", RTLD_NOW);
ASSERT_TRUE(handle != nullptr) << dlerror();
typedef int (*fn_t)();
{
fn_t fn = reinterpret_cast<fn_t>(dlvsym(handle, "versioned_function", "nonversion"));
ASSERT_TRUE(fn == nullptr);
ASSERT_SUBSTR("undefined symbol: versioned_function, version nonversion", dlerror());
}
{
fn_t fn = reinterpret_cast<fn_t>(dlvsym(handle, "versioned_function", "TESTLIB_V2"));
ASSERT_TRUE(fn != nullptr) << dlerror();
ASSERT_EQ(2, fn());
}
dlclose(handle);
}
// This preempts the implementation from libtest_versioned_lib.so
extern "C" int version_zero_function() {
return 0;