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Merge "Refactor linker allocator"

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This commit is contained in:
Dmitriy Ivanov 2014-05-13 15:49:18 +00:00 committed by Gerrit Code Review
commit d44927b8e9
6 changed files with 434 additions and 61 deletions
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3
linker/Android.mk
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@ -6,6 +6,7 @@ LOCAL_SRC_FILES:= \
debugger.cpp \
dlfcn.cpp \
linker.cpp \
linker_allocator.cpp \
linker_environ.cpp \
linker_phdr.cpp \
rt.cpp \
@ -67,3 +68,5 @@ LOCAL_INSTALLED_MODULE_STEM :=
LOCAL_INTERMEDIATE_TARGETS :=
include $(LOCAL_PATH)/linker_executable.mk
endif
include $(call first-makefiles-under,$(LOCAL_PATH))

79
linker/linker.cpp Executable file → Normal file
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@ -48,6 +48,7 @@
#include "linker_debug.h"
#include "linker_environ.h"
#include "linker_phdr.h"
#include "linker_allocator.h"
/* >>> IMPORTANT NOTE - READ ME BEFORE MODIFYING <<<
*
@ -69,14 +70,8 @@ static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
// We can't use malloc(3) in the dynamic linker. We use a linked list of anonymous
// maps, each a single page in size. The pages are broken up into as many struct soinfo
// objects as will fit, and they're all threaded together on a free list.
#define SOINFO_PER_POOL ((PAGE_SIZE - sizeof(soinfo_pool_t*)) / sizeof(soinfo))
struct soinfo_pool_t {
soinfo_pool_t* next;
soinfo info[SOINFO_PER_POOL];
};
static struct soinfo_pool_t* gSoInfoPools = NULL;
static soinfo* gSoInfoFreeList = NULL;
// objects as will fit.
static LinkerAllocator<soinfo> gSoInfoAllocator;
static soinfo* solist = &libdl_info;
static soinfo* sonext = &libdl_info;
@ -269,56 +264,13 @@ void notify_gdb_of_libraries() {
rtld_db_dlactivity();
}
static bool ensure_free_list_non_empty() {
if (gSoInfoFreeList != NULL) {
return true;
}
// Allocate a new pool.
soinfo_pool_t* pool = reinterpret_cast<soinfo_pool_t*>(mmap(NULL, sizeof(*pool),
PROT_READ|PROT_WRITE,
MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
if (pool == MAP_FAILED) {
return false;
}
// Add the pool to our list of pools.
pool->next = gSoInfoPools;
gSoInfoPools = pool;
// Chain the entries in the new pool onto the free list.
gSoInfoFreeList = &pool->info[0];
soinfo* next = NULL;
for (int i = SOINFO_PER_POOL - 1; i >= 0; --i) {
pool->info[i].next = next;
next = &pool->info[i];
}
return true;
}
static void set_soinfo_pool_protection(int protection) {
for (soinfo_pool_t* p = gSoInfoPools; p != NULL; p = p->next) {
if (mprotect(p, sizeof(*p), protection) == -1) {
abort(); // Can't happen.
}
}
}
static soinfo* soinfo_alloc(const char* name) {
if (strlen(name) >= SOINFO_NAME_LEN) {
DL_ERR("library name \"%s\" too long", name);
return NULL;
}
if (!ensure_free_list_non_empty()) {
DL_ERR("out of memory when loading \"%s\"", name);
return NULL;
}
// Take the head element off the free list.
soinfo* si = gSoInfoFreeList;
gSoInfoFreeList = gSoInfoFreeList->next;
soinfo* si = gSoInfoAllocator.alloc();
// Initialize the new element.
memset(si, 0, sizeof(soinfo));
@ -357,8 +309,8 @@ static void soinfo_free(soinfo* si) {
if (si == sonext) {
sonext = prev;
}
si->next = gSoInfoFreeList;
gSoInfoFreeList = si;
gSoInfoAllocator.free(si);
}
@ -794,8 +746,8 @@ static int soinfo_unload(soinfo* si) {
munmap(reinterpret_cast<void*>(si->base), si->size);
notify_gdb_of_unload(si);
soinfo_free(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);
@ -822,19 +774,19 @@ soinfo* do_dlopen(const char* name, int flags, const android_dlextinfo* extinfo)
DL_ERR("invalid extended flags to android_dlopen_ext: %x", extinfo->flags);
return NULL;
}
set_soinfo_pool_protection(PROT_READ | PROT_WRITE);
gSoInfoAllocator.protect_all(PROT_READ | PROT_WRITE);
soinfo* si = find_library(name, extinfo);
if (si != NULL) {
si->CallConstructors();
}
set_soinfo_pool_protection(PROT_READ);
gSoInfoAllocator.protect_all(PROT_READ);
return si;
}
int do_dlclose(soinfo* si) {
set_soinfo_pool_protection(PROT_READ | PROT_WRITE);
gSoInfoAllocator.protect_all(PROT_READ | PROT_WRITE);
int result = soinfo_unload(si);
set_soinfo_pool_protection(PROT_READ);
gSoInfoAllocator.protect_all(PROT_READ);
return result;
}
@ -1382,7 +1334,7 @@ void soinfo::CallFunction(const char* function_name __unused, linker_function_t
// 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).
set_soinfo_pool_protection(PROT_READ | PROT_WRITE);
gSoInfoAllocator.protect_all(PROT_READ | PROT_WRITE);
}
void soinfo::CallPreInitConstructors() {
@ -1933,6 +1885,11 @@ static ElfW(Addr) __linker_init_post_relocation(KernelArgumentBlock& args, ElfW(
ldpreload_env = linker_env_get("LD_PRELOAD");
}
// Linker does not call constructors for its own
// global variables so we need to initialize
// the allocator explicitly.
gSoInfoAllocator.init();
INFO("[ android linker & debugger ]");
soinfo* si = soinfo_alloc(args.argv[0]);
@ -2150,7 +2107,7 @@ extern "C" ElfW(Addr) __linker_init(void* raw_args) {
args.abort_message_ptr = &gAbortMessage;
ElfW(Addr) start_address = __linker_init_post_relocation(args, linker_addr);
set_soinfo_pool_protection(PROT_READ);
gSoInfoAllocator.protect_all(PROT_READ);
// Return the address that the calling assembly stub should jump to.
return start_address;

142
linker/linker_allocator.cpp Normal file
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@ -0,0 +1,142 @@
/*
* 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 "linker_allocator.h"
#include <inttypes.h>
#include <sys/mman.h>
#include <unistd.h>
struct LinkerAllocatorPage {
LinkerAllocatorPage* next;
uint8_t bytes[PAGE_SIZE-sizeof(LinkerAllocatorPage*)];
};
struct FreeBlockInfo {
void* next_block;
size_t num_free_blocks;
};
LinkerBlockAllocator::LinkerBlockAllocator()
: block_size_(0),
page_list_(nullptr),
free_block_list_(nullptr)
{}
void LinkerBlockAllocator::init(size_t block_size) {
block_size_ = block_size < sizeof(FreeBlockInfo) ? sizeof(FreeBlockInfo) : block_size;
}
void* LinkerBlockAllocator::alloc() {
if (free_block_list_ == nullptr) {
create_new_page();
} else {
protect_page(free_block_list_, PROT_READ | PROT_WRITE);
}
FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(free_block_list_);
if (block_info->num_free_blocks > 1) {
FreeBlockInfo* next_block_info = reinterpret_cast<FreeBlockInfo*>(
reinterpret_cast<char*>(free_block_list_) + block_size_);
next_block_info->next_block = block_info->next_block;
next_block_info->num_free_blocks = block_info->num_free_blocks - 1;
free_block_list_ = next_block_info;
} else {
free_block_list_ = block_info->next_block;
}
block_info->next_block = nullptr;
block_info->num_free_blocks = 0;
return block_info;
}
void LinkerBlockAllocator::free(void* block) {
if (block == nullptr) {
return;
}
LinkerAllocatorPage* page = find_page(block);
if (page == nullptr) {
abort();
}
ssize_t offset = reinterpret_cast<uint8_t*>(block) - page->bytes;
if (offset % block_size_ != 0) {
abort();
}
FreeBlockInfo* block_info = reinterpret_cast<FreeBlockInfo*>(block);
protect_page(block_info, PROT_READ | PROT_WRITE);
block_info->next_block = free_block_list_;
block_info->num_free_blocks = 1;
protect_page(block_info, PROT_READ);
free_block_list_ = block_info;
}
void LinkerBlockAllocator::protect_all(int prot) {
for (LinkerAllocatorPage* page = page_list_; page != nullptr; page = page->next) {
if (mprotect(page, PAGE_SIZE, prot) == -1) {
abort();
}
}
}
void LinkerBlockAllocator::protect_page(void* block, int prot) {
LinkerAllocatorPage* page = find_page(block);
if (page == nullptr || mprotect(page, PAGE_SIZE, prot) == -1) {
abort();
}
}
void LinkerBlockAllocator::create_new_page() {
LinkerAllocatorPage* page = reinterpret_cast<LinkerAllocatorPage*>(mmap(nullptr, PAGE_SIZE,
PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, 0, 0));
if (page == MAP_FAILED) {
abort(); // oom
}
FreeBlockInfo* first_block = reinterpret_cast<FreeBlockInfo*>(page->bytes);
first_block->next_block = free_block_list_;
first_block->num_free_blocks = (PAGE_SIZE - sizeof(LinkerAllocatorPage*))/block_size_;
free_block_list_ = first_block;
page->next = page_list_;
page_list_ = page;
}
LinkerAllocatorPage* LinkerBlockAllocator::find_page(void* block) {
if (block == nullptr) {
abort();
}
LinkerAllocatorPage* page = page_list_;
const uint8_t* page_ptr = reinterpret_cast<const uint8_t*>(page);
while (page != nullptr) {
if (block >= (page_ptr + sizeof(page->next)) && block < (page_ptr + PAGE_SIZE)) {
return page;
}
page = page->next;
}
abort();
}

72
linker/linker_allocator.h Normal file
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@ -0,0 +1,72 @@
/*
* 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.
*/
#ifndef __LINKER_ALLOCATOR_H
#define __LINKER_ALLOCATOR_H
#include <stdlib.h>
#include <limits.h>
#include "private/bionic_macros.h"
struct LinkerAllocatorPage;
/*
* This class is a non-template version of the LinkerAllocator
* It keeps code inside .cpp file by keeping the interface
* template-free.
*
* Please use LinkerAllocator<type> where possible (everywhere).
*/
class LinkerBlockAllocator {
public:
LinkerBlockAllocator();
void init(size_t block_size);
void* alloc();
void free(void* block);
void protect_page(void* block, int prot);
void protect_all(int prot);
private:
void create_new_page();
LinkerAllocatorPage* find_page(void* block);
size_t block_size_;
LinkerAllocatorPage* page_list_;
void* free_block_list_;
DISALLOW_COPY_AND_ASSIGN(LinkerBlockAllocator);
};
/*
* A simple allocator for the dynamic linker. An allocator allocates instances
* of a single fixed-size type. Allocations are backed by page-sized private
* anonymous mmaps.
*/
template<typename T>
class LinkerAllocator {
public:
LinkerAllocator() : block_allocator_() {}
void init() { block_allocator_.init(sizeof(T)); }
T* alloc() { return reinterpret_cast<T*>(block_allocator_.alloc()); }
void free(T* t) { block_allocator_.free(t); }
void protect_page(T* t, int prot) { block_allocator_.protect_page(t, prot); }
void protect_all(int prot) { block_allocator_.protect_all(prot); }
private:
LinkerBlockAllocator block_allocator_;
DISALLOW_COPY_AND_ASSIGN(LinkerAllocator);
};
#endif // __LINKER_ALLOCATOR_H

38
linker/tests/Android.mk Normal file
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@ -0,0 +1,38 @@
#
# Copyright (C) 2012 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.
#
ifneq ($(BUILD_TINY_ANDROID),true)
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MULTILIB := both
LOCAL_MODULE := linker-unit-tests
LOCAL_MODULE_STEM_32 := $(LOCAL_MODULE)32
LOCAL_MODULE_STEM_64 := $(LOCAL_MODULE)64
LOCAL_ADDITIONAL_DEPENDENCIES := $(LOCAL_PATH)/Android.mk
LOCAL_CFLAGS += -g -Wall -Wextra -Werror -std=gnu++11
LOCAL_C_INCLUDES := $(LOCAL_PATH)/../../libc/
LOCAL_SRC_FILES := \
linker_allocator_test.cpp \
../linker_allocator.cpp
include $(BUILD_NATIVE_TEST)
endif # !BUILD_TINY_ANDROID

161
linker/tests/linker_allocator_test.cpp Normal file
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@ -0,0 +1,161 @@
/*
* Copyright (C) 2013 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 <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <gtest/gtest.h>
#include "../linker_allocator.h"
#include <unistd.h>
namespace {
struct test_struct_nominal {
void* pointer;
ssize_t value;
};
/*
* this one has size below allocator cap which is 2*sizeof(void*)
*/
struct test_struct_small {
char dummy_str[5];
};
/*
* 1009 byte struct (1009 is prime)
*/
struct test_struct_larger {
char dummy_str[1009];
};
static size_t kPageSize = sysconf(_SC_PAGE_SIZE);
};
TEST(linker_allocator, test_nominal) {
LinkerAllocator<test_struct_nominal> allocator;
allocator.init();
test_struct_nominal* ptr1 = allocator.alloc();
ASSERT_TRUE(ptr1 != nullptr);
test_struct_nominal* ptr2 = allocator.alloc();
ASSERT_TRUE(ptr2 != nullptr);
// they should be next to each other.
ASSERT_EQ(ptr1+1, ptr2);
ptr1->value = 42;
allocator.protect_page(ptr1, PROT_READ);
allocator.free(ptr1);
allocator.free(ptr2);
}
TEST(linker_allocator, test_small) {
LinkerAllocator<test_struct_small> allocator;
allocator.init();
char* ptr1 = reinterpret_cast<char*>(allocator.alloc());
char* ptr2 = reinterpret_cast<char*>(allocator.alloc());
ASSERT_TRUE(ptr1 != nullptr);
ASSERT_TRUE(ptr2 != nullptr);
ASSERT_EQ(ptr1+2*sizeof(void*), ptr2);
}
TEST(linker_allocator, test_larger) {
LinkerAllocator<test_struct_larger> allocator;
allocator.init();
test_struct_larger* ptr1 = allocator.alloc();
test_struct_larger* ptr2 = allocator.alloc();
ASSERT_TRUE(ptr1 != nullptr);
ASSERT_TRUE(ptr2 != nullptr);
ASSERT_EQ(ptr1+1, ptr2);
allocator.protect_page(ptr2, PROT_READ);
// lets allocate until we reach next page.
size_t n = kPageSize/sizeof(test_struct_larger) + 1 - 2;
for (size_t i=0; i<n; ++i) {
ASSERT_TRUE(allocator.alloc() != nullptr);
}
}
static void protect_one_page() {
LinkerAllocator<test_struct_larger> allocator;
allocator.init();
// number of allocs to reach the end of first page
size_t n = kPageSize/sizeof(test_struct_larger) - 1;
test_struct_larger* page1_ptr = allocator.alloc();
for (size_t i=0; i<n; ++i) {
allocator.alloc();
}
test_struct_larger* page2_ptr = allocator.alloc();
allocator.protect_page(page2_ptr, PROT_READ);
// check that we still have access to page1
page1_ptr->dummy_str[17] = 52;
fprintf(stderr, "trying to access protected page");
// this should result in segmentation fault
page2_ptr->dummy_str[12] = 3;
}
static void protect_all() {
LinkerAllocator<test_struct_larger> allocator;
allocator.init();
// number of allocs to reach the end of first page
size_t n = kPageSize/sizeof(test_struct_larger) - 1;
test_struct_larger* page1_ptr = allocator.alloc();
for (size_t i=0; i<n; ++i) {
allocator.alloc();
}
test_struct_larger* page2_ptr = allocator.alloc();
allocator.protect_all(PROT_READ);
allocator.protect_all(PROT_READ | PROT_WRITE);
// check access
page2_ptr->dummy_str[23] = 27;
page1_ptr->dummy_str[13] = 11;
allocator.protect_all(PROT_READ);
fprintf(stderr, "trying to access protected page");
// this should result in segmentation fault
page1_ptr->dummy_str[11] = 7;
}
TEST(linker_allocator, test_protect) {
testing::FLAGS_gtest_death_test_style = "threadsafe";
ASSERT_EXIT(protect_one_page(), testing::KilledBySignal(SIGSEGV), "trying to access protected page");
ASSERT_EXIT(protect_all(), testing::KilledBySignal(SIGSEGV), "trying to access protected page");
}