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Cache Magisk app ID for performance

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This commit is contained in:
topjohnwu 2021-09-20 05:47:15 -07:00
parent 4f0bced53e
commit 82c7662cdf
3 changed files with 33 additions and 1 deletions
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1
native/jni/zygisk/deny/deny.hpp
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@ -25,6 +25,7 @@ void revert_daemon(int pid, int client);
void revert_unmount(int pid = -1);
extern std::atomic<bool> denylist_enabled;
extern int cached_manager_app_id;
enum : int {
ENFORCE_DENY,

1
native/jni/zygisk/deny/utils.cpp
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@ -276,6 +276,7 @@ static void inotify_handler(pollfd *pfd) {
} u{};
read(pfd->fd, u.buf, sizeof(u.buf));
if (u.event.name == "packages.xml"sv) {
cached_manager_app_id = -1;
exec_task([] {
mutex_guard lock(data_lock);
rebuild_map();

32
native/jni/zygisk/entry.cpp
View File

@ -251,11 +251,41 @@ static void setup_files(int client, ucred *cred) {
write_string(client, path);
}
int cached_manager_app_id = -1;
static time_t last_modified = 0;
static void get_app_info(int client) {
AppInfo info{};
int uid = read_int(client);
string process = read_string(client);
if (to_app_id(uid) == get_manager_app_id()) {
// This function is called on every single zygote app process specialization,
// so performance is critical. get_manager_app_id() is expensive as it goes
// through a SQLite query and potentially multiple filesystem stats, so we
// really want to cache the app ID value. Check the last modify timestamp of
// packages.xml and only re-fetch the manager app ID if something changed since
// we last checked. Granularity in seconds is good enough.
// If denylist is enabled, inotify will invalidate the app ID cache for us.
// In this case, we can skip the timestamp check all together.
int manager_app_id = cached_manager_app_id;
// Denylist not enabled, check packages.xml timestamp
if (!denylist_enabled && manager_app_id > 0) {
struct stat st{};
stat("/data/system/packages.xml", &st);
if (st.st_atim.tv_sec > last_modified) {
manager_app_id = -1;
last_modified = st.st_atim.tv_sec;
}
}
if (manager_app_id < 0) {
manager_app_id = get_manager_app_id();
cached_manager_app_id = manager_app_id;
}
if (to_app_id(uid) == manager_app_id) {
info.is_magisk_app = true;
} else if (denylist_enabled) {
info.on_denylist = is_deny_target(uid, process);