Magisk/native/jni/systemproperties/prop_area.cpp

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/*
* Copyright (C) 2008 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include "system_properties/prop_area.h"
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/cdefs.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include <unistd.h>
#include <new>
#include <async_safe/log.h>
constexpr size_t PA_SIZE = 128 * 1024;
constexpr uint32_t PROP_AREA_MAGIC = 0x504f5250;
constexpr uint32_t PROP_AREA_VERSION = 0xfc6ed0ab;
size_t prop_area::pa_size_ = 0;
size_t prop_area::pa_data_size_ = 0;
prop_area* prop_area::map_prop_area_rw(const char* filename, const char* context,
bool* fsetxattr_failed) {
/* dev is a tmpfs that we can use to carve a shared workspace
* out of, so let's do that...
*/
const int fd = open(filename, O_RDWR | O_CREAT | O_NOFOLLOW | O_CLOEXEC | O_EXCL, 0444);
if (fd < 0) {
if (errno == EACCES) {
/* for consistency with the case where the process has already
* mapped the page in and segfaults when trying to write to it
*/
abort();
}
return nullptr;
}
if (context) {
if (fsetxattr(fd, XATTR_NAME_SELINUX, context, strlen(context) + 1, 0) != 0) {
async_safe_format_log(ANDROID_LOG_ERROR, "libc",
"fsetxattr failed to set context (%s) for \"%s\"", context, filename);
/*
* fsetxattr() will fail during system properties tests due to selinux policy.
* We do not want to create a custom policy for the tester, so we will continue in
* this function but set a flag that an error has occurred.
* Init, which is the only daemon that should ever call this function will abort
* when this error occurs.
* Otherwise, the tester will ignore it and continue, albeit without any selinux
* property separation.
*/
if (fsetxattr_failed) {
*fsetxattr_failed = true;
}
}
}
if (ftruncate(fd, PA_SIZE) < 0) {
close(fd);
return nullptr;
}
pa_size_ = PA_SIZE;
pa_data_size_ = pa_size_ - sizeof(prop_area);
void* const memory_area = mmap(nullptr, pa_size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (memory_area == MAP_FAILED) {
close(fd);
return nullptr;
}
prop_area* pa = new (memory_area) prop_area(PROP_AREA_MAGIC, PROP_AREA_VERSION);
close(fd);
return pa;
}
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/* resetprop: map_fd_ro -> map_fd_rw */
prop_area* prop_area::map_fd_rw(const int fd) {
struct stat fd_stat;
if (fstat(fd, &fd_stat) < 0) {
return nullptr;
}
if ((fd_stat.st_uid != 0) || (fd_stat.st_gid != 0) ||
((fd_stat.st_mode & (S_IWGRP | S_IWOTH)) != 0) ||
(fd_stat.st_size < static_cast<off_t>(sizeof(prop_area)))) {
return nullptr;
}
pa_size_ = fd_stat.st_size;
pa_data_size_ = pa_size_ - sizeof(prop_area);
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/* resetprop: add PROT_WRITE */
void* const map_result = mmap(nullptr, pa_size_, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (map_result == MAP_FAILED) {
return nullptr;
}
prop_area* pa = reinterpret_cast<prop_area*>(map_result);
if ((pa->magic() != PROP_AREA_MAGIC) || (pa->version() != PROP_AREA_VERSION)) {
munmap(pa, pa_size_);
return nullptr;
}
return pa;
}
prop_area* prop_area::map_prop_area(const char* filename) {
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/* resetprop: O_RDONLY -> O_RDWR */
int fd = open(filename, O_CLOEXEC | O_NOFOLLOW | O_RDWR);
if (fd == -1) return nullptr;
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prop_area* map_result = map_fd_rw(fd);
close(fd);
return map_result;
}
void* prop_area::allocate_obj(const size_t size, uint_least32_t* const off) {
const size_t aligned = __BIONIC_ALIGN(size, sizeof(uint_least32_t));
if (bytes_used_ + aligned > pa_data_size_) {
return nullptr;
}
*off = bytes_used_;
bytes_used_ += aligned;
return data_ + *off;
}
prop_bt* prop_area::new_prop_bt(const char* name, uint32_t namelen, uint_least32_t* const off) {
uint_least32_t new_offset;
void* const p = allocate_obj(sizeof(prop_bt) + namelen + 1, &new_offset);
if (p != nullptr) {
prop_bt* bt = new (p) prop_bt(name, namelen);
*off = new_offset;
return bt;
}
return nullptr;
}
prop_info* prop_area::new_prop_info(const char* name, uint32_t namelen, const char* value,
uint32_t valuelen, uint_least32_t* const off) {
uint_least32_t new_offset;
void* const p = allocate_obj(sizeof(prop_info) + namelen + 1, &new_offset);
if (p == nullptr) return nullptr;
prop_info* info;
if (valuelen >= PROP_VALUE_MAX) {
uint32_t long_value_offset = 0;
char* long_location = reinterpret_cast<char*>(allocate_obj(valuelen + 1, &long_value_offset));
if (!long_location) return nullptr;
memcpy(long_location, value, valuelen);
long_location[valuelen] = '\0';
// Both new_offset and long_value_offset are offsets based off of data_, however prop_info
// does not know what data_ is, so we change this offset to be an offset from the prop_info
// pointer that contains it.
long_value_offset -= new_offset;
info = new (p) prop_info(name, namelen, long_value_offset);
} else {
info = new (p) prop_info(name, namelen, value, valuelen);
}
*off = new_offset;
return info;
}
void* prop_area::to_prop_obj(uint_least32_t off) {
if (off > pa_data_size_) return nullptr;
return (data_ + off);
}
inline prop_bt* prop_area::to_prop_bt(atomic_uint_least32_t* off_p) {
uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
return reinterpret_cast<prop_bt*>(to_prop_obj(off));
}
inline prop_info* prop_area::to_prop_info(atomic_uint_least32_t* off_p) {
uint_least32_t off = atomic_load_explicit(off_p, memory_order_consume);
return reinterpret_cast<prop_info*>(to_prop_obj(off));
}
inline prop_bt* prop_area::root_node() {
return reinterpret_cast<prop_bt*>(to_prop_obj(0));
}
static int cmp_prop_name(const char* one, uint32_t one_len, const char* two, uint32_t two_len) {
if (one_len < two_len)
return -1;
else if (one_len > two_len)
return 1;
else
return strncmp(one, two, one_len);
}
prop_bt* prop_area::find_prop_bt(prop_bt* const bt, const char* name, uint32_t namelen,
bool alloc_if_needed) {
prop_bt* current = bt;
while (true) {
if (!current) {
return nullptr;
}
const int ret = cmp_prop_name(name, namelen, current->name, current->namelen);
if (ret == 0) {
return current;
}
if (ret < 0) {
uint_least32_t left_offset = atomic_load_explicit(&current->left, memory_order_relaxed);
if (left_offset != 0) {
current = to_prop_bt(&current->left);
} else {
if (!alloc_if_needed) {
return nullptr;
}
uint_least32_t new_offset;
prop_bt* new_bt = new_prop_bt(name, namelen, &new_offset);
if (new_bt) {
atomic_store_explicit(&current->left, new_offset, memory_order_release);
}
return new_bt;
}
} else {
uint_least32_t right_offset = atomic_load_explicit(&current->right, memory_order_relaxed);
if (right_offset != 0) {
current = to_prop_bt(&current->right);
} else {
if (!alloc_if_needed) {
return nullptr;
}
uint_least32_t new_offset;
prop_bt* new_bt = new_prop_bt(name, namelen, &new_offset);
if (new_bt) {
atomic_store_explicit(&current->right, new_offset, memory_order_release);
}
return new_bt;
}
}
}
}
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prop_bt *prop_area::find_prop_bt(prop_bt *const trie, const char *name, bool alloc_if_needed) {
if (!trie) return nullptr;
const char* remaining_name = name;
prop_bt* current = trie;
while (true) {
const char* sep = strchr(remaining_name, '.');
const bool want_subtree = (sep != nullptr);
const uint32_t substr_size = (want_subtree) ? sep - remaining_name : strlen(remaining_name);
if (!substr_size) {
return nullptr;
}
prop_bt* root = nullptr;
uint_least32_t children_offset = atomic_load_explicit(&current->children, memory_order_relaxed);
if (children_offset != 0) {
root = to_prop_bt(&current->children);
} else if (alloc_if_needed) {
uint_least32_t new_offset;
root = new_prop_bt(remaining_name, substr_size, &new_offset);
if (root) {
atomic_store_explicit(&current->children, new_offset, memory_order_release);
}
}
if (!root) {
return nullptr;
}
current = find_prop_bt(root, remaining_name, substr_size, alloc_if_needed);
if (!current) {
return nullptr;
}
if (!want_subtree) break;
remaining_name = sep + 1;
}
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return current;
}
const prop_info* prop_area::find_property(prop_bt* const trie, const char* name, uint32_t namelen,
const char* value, uint32_t valuelen,
bool alloc_if_needed) {
const char* remaining_name = name;
prop_bt* current = find_prop_bt(trie, name, alloc_if_needed);
if (!current)
return nullptr;
uint_least32_t prop_offset = atomic_load_explicit(&current->prop, memory_order_relaxed);
if (prop_offset != 0) {
return to_prop_info(&current->prop);
} else if (alloc_if_needed) {
uint_least32_t new_offset;
prop_info* new_info = new_prop_info(name, namelen, value, valuelen, &new_offset);
if (new_info) {
atomic_store_explicit(&current->prop, new_offset, memory_order_release);
}
return new_info;
} else {
return nullptr;
}
}
bool prop_area::foreach_property(prop_bt* const trie,
void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
if (!trie) return false;
uint_least32_t left_offset = atomic_load_explicit(&trie->left, memory_order_relaxed);
if (left_offset != 0) {
const int err = foreach_property(to_prop_bt(&trie->left), propfn, cookie);
if (err < 0) return false;
}
uint_least32_t prop_offset = atomic_load_explicit(&trie->prop, memory_order_relaxed);
if (prop_offset != 0) {
prop_info* info = to_prop_info(&trie->prop);
if (!info) return false;
propfn(info, cookie);
}
uint_least32_t children_offset = atomic_load_explicit(&trie->children, memory_order_relaxed);
if (children_offset != 0) {
const int err = foreach_property(to_prop_bt(&trie->children), propfn, cookie);
if (err < 0) return false;
}
uint_least32_t right_offset = atomic_load_explicit(&trie->right, memory_order_relaxed);
if (right_offset != 0) {
const int err = foreach_property(to_prop_bt(&trie->right), propfn, cookie);
if (err < 0) return false;
}
return true;
}
const prop_info* prop_area::find(const char* name) {
return find_property(root_node(), name, strlen(name), nullptr, 0, false);
}
bool prop_area::add(const char* name, unsigned int namelen, const char* value,
unsigned int valuelen) {
return find_property(root_node(), name, namelen, value, valuelen, true);
}
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bool prop_area::del(const char *name) {
prop_bt* node = find_prop_bt(root_node(), name, false);
if (!node)
return false;
atomic_store_explicit(&node->prop, 0, memory_order_release);
return true;
}
bool prop_area::foreach (void (*propfn)(const prop_info* pi, void* cookie), void* cookie) {
return foreach_property(root_node(), propfn, cookie);
}