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am 63ea43de: am e942b3ed: Merge "Added test for ifunc support in dynamic linker."

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* commit '63ea43de8f2f5aa5c260165a1d4415f642656d75':
  Added test for ifunc support in dynamic linker.
This commit is contained in:
Dmitriy Ivanov
2014-08-14 00:38:50 +00:00
committed by Android Git Automerger
parent 89c57c8728 63ea43de8f
commit 3435d89666
7 changed files with 214 additions and 10 deletions
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3
libc/include/elf.h
View File

@@ -74,9 +74,12 @@ typedef struct {
#define STB_LOPROC 13
#define STB_HIPROC 15
#define STT_GNU_IFUNC 10
#define STT_LOOS 10
#define STT_HIOS 12
#define STT_LOPROC 13
#define STT_HIPROC 15
#define R_386_IRELATIVE 42
#endif /* _ELF_H */

110
linker/linker.cpp
View File

@@ -476,6 +476,29 @@ static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name,
return NULL;
}
static void resolve_ifunc_symbols(soinfo* si) {
phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias);
TRACE_TYPE(IFUNC, "CHECKING FOR IFUNCS AND PERFORMING SYMBOL UPDATES");
for (size_t i = 0; i < si->nchain; ++i) {
ElfW(Sym)* s = &si->symtab[i];
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
// The address of the ifunc in the symbol table is the address of the
// function that chooses the function to which the ifunc will refer.
// In order to return the proper value, we run the choosing function
// in the linker and then return its result (minus the base offset).
TRACE_TYPE(IFUNC, "FOUND IFUNC");
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
s->st_value = (ifunc_ptr() - si->base);
TRACE_TYPE(IFUNC, "NEW VALUE IS %p", (void*)s->st_value);
}
}
phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias);
}
static unsigned elfhash(const char* _name) {
const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
unsigned h = 0, g;
@@ -798,6 +821,10 @@ static soinfo* load_library(const char* name, int dlflags, const android_dlextin
return NULL;
}
// if the library has any ifuncs, we will need to resolve them so that dlsym
// can handle them properly
resolve_ifunc_symbols(si);
return si;
}
@@ -911,6 +938,53 @@ void do_dlclose(soinfo* si) {
protect_data(PROT_READ);
}
// ifuncs are only defined for x86
#if defined(__i386__)
static void soinfo_ifunc_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) {
for (size_t idx = 0; idx < count; ++idx, ++rel) {
ElfW(Sym)* s;
soinfo* lsi;
unsigned type = ELFW(R_TYPE)(rel->r_info);
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;
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC && type == R_386_JMP_SLOT) {
TRACE("IFUNC RELOCATION, PASS 2: %p", (void*)(sym_addr));
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
*reinterpret_cast<ElfW(Addr)*>(reloc) = ifunc_ptr();
}
}
}
#endif
#if defined(__x86_64__)
static void soinfo_ifunc_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
for (size_t idx = 0; idx < count; ++idx, ++rela) {
ElfW(Sym)* s;
soinfo* lsi;
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;
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC && type == R_X86_64_JUMP_SLOT) {
TRACE("IFUNC RELOCATION, PASS 2: %p", (void*)(sym_addr + rela->r_addend));
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
*reinterpret_cast<ElfW(Addr)*>(reloc) = ifunc_ptr();
}
}
}
#endif
#if defined(USE_RELA)
static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
ElfW(Sym)* s;
@@ -1122,7 +1196,11 @@ static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo*
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);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
si->set_has_ifuncs(true);
} else {
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
}
break;
case R_X86_64_GLOB_DAT:
count_relocation(kRelocAbsolute);
@@ -1301,7 +1379,11 @@ static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* n
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
si->set_has_ifuncs(true);
} else {
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
}
break;
case R_386_GLOB_DAT:
count_relocation(kRelocAbsolute);
@@ -1561,6 +1643,14 @@ void soinfo::set_st_ino(ino_t ino) {
st_ino = ino;
}
void soinfo::set_has_ifuncs(bool ifuncs) {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return;
}
has_ifuncs = ifuncs;
}
dev_t soinfo::get_st_dev() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return 0;
@@ -1577,6 +1667,14 @@ ino_t soinfo::get_st_ino() {
return st_ino;
}
bool soinfo::get_has_ifuncs() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return false;
}
return has_ifuncs;
}
// 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;
@@ -1961,6 +2059,18 @@ static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) {
}
#endif
// if there are ifuncs, we need to do an additional relocation pass.
// they cannot be resolved until the rest of the relocations are done
// because we need to call the resolution function which may be waiting
// on relocations.
if(si->get_has_ifuncs()) {
#if defined(__i386__)
soinfo_ifunc_relocate(si, si->plt_rel, si->plt_rel_count, needed);
#elif defined(__x86_64__)
soinfo_ifunc_relocate(si, si->plt_rela, si->plt_rela_count, needed);
#endif
}
#if defined(__mips__)
if (!mips_relocate_got(si, needed)) {
return false;

6
linker/linker.h
View File

@@ -204,8 +204,12 @@ struct soinfo {
void set_st_dev(dev_t st_dev);
void set_st_ino(ino_t st_ino);
void set_has_ifuncs(bool ifunc);
ino_t get_st_ino();
dev_t get_st_dev();
bool get_has_ifuncs();
soinfo_list_t& get_children();
@@ -218,6 +222,8 @@ struct soinfo {
// when FLAG_NEW_SOINFO is set in this->flags.
unsigned int version;
bool has_ifuncs;
dev_t st_dev;
ino_t st_ino;

1
linker/linker_debug.h
View File

@@ -42,6 +42,7 @@
#define TRACE_DEBUG 1
#define DO_TRACE_LOOKUP 1
#define DO_TRACE_RELO 1
#define DO_TRACE_IFUNC 1
#define TIMING 0
#define STATS 0
#define COUNT_PAGES 0

33
tests/dlfcn_test.cpp
View File

@@ -106,6 +106,39 @@ TEST(dlfcn, dlopen_noload) {
ASSERT_EQ(0, dlclose(handle2));
}
// ifuncs are only supported on intel for now
#if defined(__i386__) || defined(__x86_64__)
TEST(dlfcn, ifunc) {
const char* (*foo_ptr)();
const char* (*foo_library_ptr)();
// ifunc's choice depends on whether IFUNC_CHOICE has a value
// first check the set case
setenv("IFUNC_CHOICE", "set", 1);
void* handle = dlopen("libtest_ifunc.so", RTLD_NOW);
ASSERT_TRUE(handle != NULL);
*(void **)(&foo_ptr) = dlsym(handle, "foo");
*(void **)(&foo_library_ptr) = dlsym(handle, "foo_library");
ASSERT_TRUE(foo_ptr != NULL);
ASSERT_TRUE(foo_library_ptr != NULL);
ASSERT_EQ(strncmp("set", (*foo_ptr)(), 3), 0);
ASSERT_EQ(strncmp("set", (*foo_library_ptr)(), 3), 0);
dlclose(handle);
// then check the unset case
unsetenv("IFUNC_CHOICE");
handle = dlopen("libtest_ifunc.so", RTLD_NOW);
ASSERT_TRUE(handle != NULL);
*(void **)(&foo_ptr) = dlsym(handle, "foo");
*(void **)(&foo_library_ptr) = dlsym(handle, "foo_library");
ASSERT_TRUE(foo_ptr != NULL);
ASSERT_TRUE(foo_library_ptr != NULL);
ASSERT_EQ(strncmp("unset", (*foo_ptr)(), 5), 0);
ASSERT_EQ(strncmp("unset", (*foo_library_ptr)(), 3), 0);
dlclose(handle);
}
#endif
TEST(dlfcn, dlopen_failure) {
void* self = dlopen("/does/not/exist", RTLD_NOW);
ASSERT_TRUE(self == NULL);

14
tests/libs/Android.mk
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@@ -114,6 +114,20 @@ build_type := target
build_target := SHARED_LIBRARY
include $(TEST_PATH)/Android.build.mk
# -----------------------------------------------------------------------------
# Library used by ifunc tests
# -----------------------------------------------------------------------------
ifeq ($(TARGET_ARCH),$(filter $(TARGET_ARCH),x86 x86_64))
libtest_ifunc_src_files := \
dlopen_testlib_ifunc.c
LOCAL_SDK_VERSION := current
module := libtest_ifunc
build_type := target
build_target := SHARED_LIBRARY
include $(TEST_PATH)/Android.build.mk
endif
# -----------------------------------------------------------------------------
# Library used to test local symbol lookup
# -----------------------------------------------------------------------------

37
tests/libs/dlopen_testlib_ifunc.c Normal file
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@@ -0,0 +1,37 @@
/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stdio.h>
#include <stdlib.h>
const char* foo() __attribute__ ((ifunc ("foo_ifunc")));
const char* f1() {
return "unset";
}
const char* f2() {
return "set";
}
void* foo_ifunc() {
char* choice = getenv("IFUNC_CHOICE");
return choice == NULL ? f1 : f2;
}
const char* foo_library() {
return foo();
}