/*
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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/context_node.h"
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#include <limits.h>
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#include <unistd.h>
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#include <async_safe/log.h>
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#include "system_properties/system_properties.h"
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// pthread_mutex_lock() calls into system_properties in the case of contention.
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// This creates a risk of dead lock if any system_properties functions
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// use pthread locks after system_property initialization.
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//
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// For this reason, the below three functions use a bionic Lock and static
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// allocation of memory for each filename.
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bool ContextNode::Open(bool access_rw, bool* fsetxattr_failed) {
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lock_.lock();
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if (pa_) {
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lock_.unlock();
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return true;
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}
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char filename[PROP_FILENAME_MAX];
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int len = async_safe_format_buffer(filename, sizeof(filename), "%s/%s", filename_, context_);
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if (len < 0 || len >= PROP_FILENAME_MAX) {
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lock_.unlock();
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return false;
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}
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if (access_rw) {
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pa_ = prop_area::map_prop_area_rw(filename, context_, fsetxattr_failed);
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} else {
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pa_ = prop_area::map_prop_area(filename);
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}
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lock_.unlock();
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return pa_;
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}
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bool ContextNode::CheckAccessAndOpen() {
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if (!pa_ && !no_access_) {
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if (!CheckAccess() || !Open(false, nullptr)) {
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no_access_ = true;
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}
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}
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return pa_;
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}
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void ContextNode::ResetAccess() {
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if (!CheckAccess()) {
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Unmap();
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no_access_ = true;
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} else {
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no_access_ = false;
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}
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}
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bool ContextNode::CheckAccess() {
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char filename[PROP_FILENAME_MAX];
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int len = async_safe_format_buffer(filename, sizeof(filename), "%s/%s", filename_, context_);
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if (len < 0 || len >= PROP_FILENAME_MAX) {
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return false;
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}
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return access(filename, R_OK) == 0;
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}
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void ContextNode::Unmap() {
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prop_area::unmap_prop_area(&pa_);
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}
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