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https://github.com/topjohnwu/Magisk.git
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402 lines
12 KiB
C++
402 lines
12 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include "system_properties/system_properties.h"
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#include <errno.h>
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#include <stdatomic.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <new>
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#include <async_safe/log.h>
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#include "private/ErrnoRestorer.h"
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#include "private/bionic_futex.h"
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#include "system_properties/context_node.h"
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#include "system_properties/prop_area.h"
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#include "system_properties/prop_info.h"
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#define SERIAL_DIRTY(serial) ((serial)&1)
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#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
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static bool is_dir(const char* pathname) {
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struct stat info;
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if (stat(pathname, &info) == -1) {
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return false;
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}
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return S_ISDIR(info.st_mode);
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}
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bool SystemProperties::Init(const char* filename) {
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// This is called from __libc_init_common, and should leave errno at 0 (http://b/37248982).
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ErrnoRestorer errno_restorer;
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if (initialized_) {
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/* resetprop remove */
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// contexts_->ResetAccess();
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return true;
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}
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if (strlen(filename) >= PROP_FILENAME_MAX) {
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return false;
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}
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strcpy(property_filename_, filename);
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if (is_dir(property_filename_)) {
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if (access("/dev/__properties__/property_info", R_OK) == 0) {
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contexts_ = new (contexts_data_) ContextsSerialized();
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if (!contexts_->Initialize(false, property_filename_, nullptr)) {
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return false;
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}
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} else {
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contexts_ = new (contexts_data_) ContextsSplit();
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if (!contexts_->Initialize(false, property_filename_, nullptr)) {
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return false;
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}
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}
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} else {
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contexts_ = new (contexts_data_) ContextsPreSplit();
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if (!contexts_->Initialize(false, property_filename_, nullptr)) {
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return false;
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}
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}
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initialized_ = true;
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return true;
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}
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bool SystemProperties::AreaInit(const char* filename, bool* fsetxattr_failed) {
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if (strlen(filename) >= PROP_FILENAME_MAX) {
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return false;
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}
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strcpy(property_filename_, filename);
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contexts_ = new (contexts_data_) ContextsSerialized();
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if (!contexts_->Initialize(true, property_filename_, fsetxattr_failed)) {
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return false;
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}
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initialized_ = true;
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return true;
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}
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uint32_t SystemProperties::AreaSerial() {
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if (!initialized_) {
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return -1;
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}
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prop_area* pa = contexts_->GetSerialPropArea();
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if (!pa) {
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return -1;
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}
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// Make sure this read fulfilled before __system_property_serial
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return atomic_load_explicit(pa->serial(), memory_order_acquire);
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}
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const prop_info* SystemProperties::Find(const char* name) {
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if (!initialized_) {
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return nullptr;
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}
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prop_area* pa = contexts_->GetPropAreaForName(name);
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if (!pa) {
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async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied finding property \"%s\"", name);
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return nullptr;
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}
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return pa->find(name);
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}
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static bool is_read_only(const char* name) {
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return strncmp(name, "ro.", 3) == 0;
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}
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int SystemProperties::Read(const prop_info* pi, char* name, char* value) {
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while (true) {
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uint32_t serial = Serial(pi); // acquire semantics
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size_t len = SERIAL_VALUE_LEN(serial);
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memcpy(value, pi->value, len + 1);
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// TODO: Fix the synchronization scheme here.
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// There is no fully supported way to implement this kind
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// of synchronization in C++11, since the memcpy races with
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// updates to pi, and the data being accessed is not atomic.
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// The following fence is unintuitive, but would be the
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// correct one if memcpy used memory_order_relaxed atomic accesses.
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// In practice it seems unlikely that the generated code would
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// would be any different, so this should be OK.
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atomic_thread_fence(memory_order_acquire);
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if (serial == load_const_atomic(&(pi->serial), memory_order_relaxed)) {
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if (name != nullptr) {
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size_t namelen = strlcpy(name, pi->name, PROP_NAME_MAX);
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if (namelen >= PROP_NAME_MAX) {
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async_safe_format_log(ANDROID_LOG_ERROR, "libc",
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"The property name length for \"%s\" is >= %d;"
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" please use __system_property_read_callback"
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" to read this property. (the name is truncated to \"%s\")",
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pi->name, PROP_NAME_MAX - 1, name);
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}
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}
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if (is_read_only(pi->name) && pi->is_long()) {
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async_safe_format_log(
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ANDROID_LOG_ERROR, "libc",
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"The property \"%s\" has a value with length %zu that is too large for"
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" __system_property_get()/__system_property_read(); use"
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" __system_property_read_callback() instead.",
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pi->name, strlen(pi->long_value()));
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}
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return len;
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}
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}
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}
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void SystemProperties::ReadCallback(const prop_info* pi,
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void (*callback)(void* cookie, const char* name,
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const char* value, uint32_t serial),
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void* cookie) {
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// Read only properties don't need to copy the value to a temporary buffer, since it can never
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// change.
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if (is_read_only(pi->name)) {
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uint32_t serial = Serial(pi);
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if (pi->is_long()) {
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callback(cookie, pi->name, pi->long_value(), serial);
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} else {
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callback(cookie, pi->name, pi->value, serial);
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}
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return;
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}
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while (true) {
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uint32_t serial = Serial(pi); // acquire semantics
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size_t len = SERIAL_VALUE_LEN(serial);
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char value_buf[len + 1];
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memcpy(value_buf, pi->value, len);
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value_buf[len] = '\0';
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// TODO: see todo in Read function
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atomic_thread_fence(memory_order_acquire);
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if (serial == load_const_atomic(&(pi->serial), memory_order_relaxed)) {
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callback(cookie, pi->name, value_buf, serial);
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return;
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}
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}
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}
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int SystemProperties::Get(const char* name, char* value) {
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const prop_info* pi = Find(name);
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if (pi != nullptr) {
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return Read(pi, nullptr, value);
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} else {
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value[0] = 0;
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return 0;
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}
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}
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int SystemProperties::Update(prop_info* pi, const char* value, unsigned int len) {
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if (len >= PROP_VALUE_MAX) {
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return -1;
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}
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if (!initialized_) {
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return -1;
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}
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prop_area* pa = contexts_->GetSerialPropArea();
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if (!pa) {
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return -1;
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}
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uint32_t serial = atomic_load_explicit(&pi->serial, memory_order_relaxed);
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serial |= 1;
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atomic_store_explicit(&pi->serial, serial, memory_order_relaxed);
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// The memcpy call here also races. Again pretend it
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// used memory_order_relaxed atomics, and use the analogous
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// counterintuitive fence.
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atomic_thread_fence(memory_order_release);
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strlcpy(pi->value, value, len + 1);
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atomic_store_explicit(&pi->serial, (len << 24) | ((serial + 1) & 0xffffff), memory_order_release);
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__futex_wake(&pi->serial, INT32_MAX);
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atomic_store_explicit(pa->serial(), atomic_load_explicit(pa->serial(), memory_order_relaxed) + 1,
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memory_order_release);
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__futex_wake(pa->serial(), INT32_MAX);
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return 0;
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}
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int SystemProperties::Add(const char* name, unsigned int namelen, const char* value,
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unsigned int valuelen) {
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if (valuelen >= PROP_VALUE_MAX && !is_read_only(name)) {
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return -1;
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}
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if (namelen < 1) {
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return -1;
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}
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if (!initialized_) {
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return -1;
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}
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prop_area* serial_pa = contexts_->GetSerialPropArea();
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if (serial_pa == nullptr) {
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return -1;
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}
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prop_area* pa = contexts_->GetPropAreaForName(name);
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if (!pa) {
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async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied adding property \"%s\"", name);
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return -1;
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}
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bool ret = pa->add(name, namelen, value, valuelen);
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if (!ret) {
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return -1;
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}
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// There is only a single mutator, but we want to make sure that
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// updates are visible to a reader waiting for the update.
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atomic_store_explicit(serial_pa->serial(),
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atomic_load_explicit(serial_pa->serial(), memory_order_relaxed) + 1,
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memory_order_release);
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__futex_wake(serial_pa->serial(), INT32_MAX);
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return 0;
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}
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int SystemProperties::Delete(const char *name) {
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if (!initialized_) {
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return -1;
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}
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prop_area* serial_pa = contexts_->GetSerialPropArea();
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if (serial_pa == nullptr) {
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return -1;
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}
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prop_area* pa = contexts_->GetPropAreaForName(name);
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if (!pa) {
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async_safe_format_log(ANDROID_LOG_ERROR, "libc", "Access denied adding property \"%s\"", name);
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return -1;
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}
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bool ret = pa->del(name);
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if (!ret) {
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return -1;
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}
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// There is only a single mutator, but we want to make sure that
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// updates are visible to a reader waiting for the update.
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atomic_store_explicit(serial_pa->serial(),
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atomic_load_explicit(serial_pa->serial(), memory_order_relaxed) + 1,
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memory_order_release);
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__futex_wake(serial_pa->serial(), INT32_MAX);
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return 0;
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}
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// Wait for non-locked serial, and retrieve it with acquire semantics.
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uint32_t SystemProperties::Serial(const prop_info* pi) {
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uint32_t serial = load_const_atomic(&pi->serial, memory_order_acquire);
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while (SERIAL_DIRTY(serial)) {
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__futex_wait(const_cast<_Atomic(uint_least32_t)*>(&pi->serial), serial, nullptr);
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serial = load_const_atomic(&pi->serial, memory_order_acquire);
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}
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return serial;
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}
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uint32_t SystemProperties::WaitAny(uint32_t old_serial) {
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uint32_t new_serial;
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Wait(nullptr, old_serial, &new_serial, nullptr);
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return new_serial;
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}
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bool SystemProperties::Wait(const prop_info* pi, uint32_t old_serial, uint32_t* new_serial_ptr,
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const timespec* relative_timeout) {
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// Are we waiting on the global serial or a specific serial?
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atomic_uint_least32_t* serial_ptr;
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if (pi == nullptr) {
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if (!initialized_) {
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return -1;
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}
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prop_area* serial_pa = contexts_->GetSerialPropArea();
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if (serial_pa == nullptr) {
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return -1;
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}
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serial_ptr = serial_pa->serial();
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} else {
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serial_ptr = const_cast<atomic_uint_least32_t*>(&pi->serial);
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}
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uint32_t new_serial;
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do {
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int rc;
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if ((rc = __futex_wait(serial_ptr, old_serial, relative_timeout)) != 0 && rc == -ETIMEDOUT) {
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return false;
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}
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new_serial = load_const_atomic(serial_ptr, memory_order_acquire);
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} while (new_serial == old_serial);
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*new_serial_ptr = new_serial;
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return true;
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}
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const prop_info* SystemProperties::FindNth(unsigned n) {
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struct find_nth {
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const uint32_t sought;
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uint32_t current;
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const prop_info* result;
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explicit find_nth(uint32_t n) : sought(n), current(0), result(nullptr) {
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}
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static void fn(const prop_info* pi, void* ptr) {
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find_nth* self = reinterpret_cast<find_nth*>(ptr);
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if (self->current++ == self->sought) self->result = pi;
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}
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} state(n);
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Foreach(find_nth::fn, &state);
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return state.result;
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}
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int SystemProperties::Foreach(void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
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if (!initialized_) {
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return -1;
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}
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contexts_->ForEach(propfn, cookie);
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return 0;
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}
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