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Remove unnecessary mirror for magic mount

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Mirror was previously used for accessing the original file during
magic mount when we are using a tmpfs to cover the target. However,
since we introduce atomic mount, we switch all tmpfs mount in
worker and then move to the target at once. It means that we can
still access the original file when we are constructing the tmpfs
mount point. Thus we no longer need mirror.
This commit is contained in:
LoveSy
2024-01-05 00:42:33 +08:00
committed by John Wu
parent d20b30c771
commit 92b305a389
3 changed files with 40 additions and 93 deletions
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48
native/src/core/module.cpp
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@@ -27,24 +27,18 @@ static int bind_mount(const char *reason, const char *from, const char *to) {
*************************/
tmpfs_node::tmpfs_node(node_entry *node) : dir_node(node, this) {
if (!skip_mirror()) {
string mirror = mirror_path();
if (auto dir = open_dir(mirror.data())) {
if (!replace()) {
if (auto dir = open_dir(node_path().data())) {
set_exist(true);
for (dirent *entry; (entry = xreaddir(dir.get()));) {
if (entry->d_type == DT_DIR) {
// create a dummy inter_node to upgrade later
emplace<inter_node>(entry->d_name, entry->d_name);
} else {
// Insert mirror nodes
emplace<mirror_node>(entry->d_name, entry);
}
// create a dummy inter_node to upgrade later
emplace<inter_node>(entry->d_name, entry);
}
}
}
for (auto it = children.begin(); it != children.end(); ++it) {
// Need to upgrade all inter_node children to tmpfs_node
// Upgrade resting inter_node children to tmpfs_node
if (isa<inter_node>(it->second))
it = upgrade<tmpfs_node>(it);
}
@@ -52,7 +46,7 @@ tmpfs_node::tmpfs_node(node_entry *node) : dir_node(node, this) {
bool dir_node::prepare() {
// If direct replace or not exist, mount ourselves as tmpfs
bool upgrade_to_tmpfs = skip_mirror() || !exist();
bool upgrade_to_tmpfs = replace() || !exist();
for (auto it = children.begin(); it != children.end();) {
// We also need to upgrade to tmpfs node if any child:
@@ -77,9 +71,9 @@ bool dir_node::prepare() {
upgrade_to_tmpfs = true;
}
if (auto dn = dyn_cast<dir_node>(it->second)) {
if (skip_mirror()) {
if (replace()) {
// Propagate skip mirror state to all children
dn->set_skip_mirror(true);
dn->set_replace(true);
}
if (dn->prepare()) {
// Upgrade child to tmpfs
@@ -98,7 +92,7 @@ void dir_node::collect_module_files(const char *module, int dfd) {
for (dirent *entry; (entry = xreaddir(dir.get()));) {
if (entry->d_name == ".replace"sv) {
set_skip_mirror(true);
set_replace(true);
continue;
}
@@ -141,18 +135,12 @@ void node_entry::create_and_mount(const char *reason, const string &src, bool ro
}
}
void mirror_node::mount() {
create_and_mount("mirror", mirror_path());
}
void module_node::mount() {
std::string path = module + (parent()->root()->prefix + node_path());
string mnt_src = module_mnt + path;
{
string src = MODULEROOT "/" + path;
if (exist()) clone_attr(mirror_path().data(), src.data());
// special case for /system/etc/hosts to ensure it is writable
if (node_path() == "/system/etc/hosts") mnt_src = std::move(src);
if (exist()) clone_attr(node_path().data(), src.data());
}
if (isa<tmpfs_node>(parent())) {
create_and_mount("module", mnt_src);
@@ -162,22 +150,23 @@ void module_node::mount() {
}
void tmpfs_node::mount() {
string src = mirror_path();
const char *src_path = access(src.data(), F_OK) == 0 ? src.data() : nullptr;
if (!is_dir()) {
create_and_mount("mirror", node_path());
return;
}
if (!isa<tmpfs_node>(parent())) {
const string &dest = node_path();
auto worker_dir = worker_path();
mkdirs(worker_dir.data(), 0);
bind_mount("tmpfs", worker_dir.data(), worker_dir.data());
clone_attr(src_path ?: parent()->node_path().data(), worker_dir.data());
clone_attr(exist() ? node_path().data() : parent()->node_path().data(), worker_dir.data());
dir_node::mount();
VLOGD(skip_mirror() ? "replace" : "move", worker_dir.data(), dest.data());
xmount(worker_dir.data(), dest.data(), nullptr, MS_MOVE, nullptr);
VLOGD(replace() ? "replace" : "move", worker_dir.data(), node_path().data());
xmount(worker_dir.data(), node_path().data(), nullptr, MS_MOVE, nullptr);
} else {
const string dest = worker_path();
// We don't need another layer of tmpfs if parent is tmpfs
mkdir(dest.data(), 0);
clone_attr(src_path ?: parent()->worker_path().data(), dest.data());
clone_attr(exist() ? node_path().data() : parent()->worker_path().data(), dest.data());
dir_node::mount();
}
}
@@ -265,7 +254,6 @@ static void inject_zygisk_libs(root_node *system) {
vector<module_info> *module_list;
void load_modules() {
node_entry::mirror_dir = get_magisk_tmp() + "/"s MIRRDIR;
node_entry::module_mnt = get_magisk_tmp() + "/"s MODULEMNT "/";
auto root = make_unique<root_node>("");