Added root companion and logging macros

module/jni/include/logging.hpp

@@ -6,10 +6,10 @@
 #ifndef NDEBUG
 static constexpr auto TAG = "ZygiskAssistant/JNI";
 #define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG, TAG, __VA_ARGS__)
-#define LOGI(...) __android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)
+#define LOGW(...) __android_log_print(ANDROID_LOG_WARN, TAG, __VA_ARGS__)
 #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, TAG, __VA_ARGS__)
 #else
 #define LOGD(...)
-#define LOGI(...)
+#define LOGW(...)
 #define LOGE(...)
 #endif

module/jni/include/utils.hpp

@@ -1,10 +1,20 @@
 #pragma once
 #include <string>
+#include <errno.h>
+#include "logging.hpp"
 #include "zygisk.hpp"
 
 #define DCL_HOOK_FUNC(ret, func, ...) \
     ret (*old_##func)(__VA_ARGS__) = nullptr;   \
     ret new_##func(__VA_ARGS__)
 
+#define ASSERT_LOG(tag, expr) if(!(expr)) { \
+    LOGE("%s:%d Assertion %s failed. %d:%s", tag, __LINE__, #expr, errno, std::strerror(errno)); }
+
+#define ASSERT_EXIT(tag, expr, ret) if(!(expr)) { \
+    LOGE("%s:%d Assertion %s failed. %d:%s", tag, __LINE__, #expr, errno, std::strerror(errno)); \
+    ret; }
+
+bool switchMountNS(int pid);
 int isUserAppUID(int uid);
 bool hookPLTByName(zygisk::Api *api, const std::string &libName, const std::string &symbolName, void *hookFunc, void **origFunc);

module/jni/main.cpp

@@ -1,6 +1,10 @@
 #include <unistd.h>
 #include <sched.h>
 #include <sys/mount.h>
+#include <grp.h>
+
+#include <cstdint>
+#include <functional>
 
 #include "zygisk.hpp"
 #include "logging.hpp"
@@ -13,6 +17,8 @@ using zygisk::ServerSpecializeArgs;
 void doUnmount();
 void doRemount();
 
+static std::function<void()> callbackFunction = []() {};
+
 /*
  * [What's the purpose of this hook?]
  * Calling unshare twice invalidates existing FD links, which fails Zygote sanity checks.
@@ -28,9 +34,7 @@ void doRemount();
  */
 DCL_HOOK_FUNC(static int, unshare, int flags)
 {
-    doUnmount();
+    callbackFunction();
-    doRemount();
-
     // Do not allow CLONE_NEWNS.
     flags &= ~(CLONE_NEWNS);
     if (!flags)
@@ -68,27 +72,41 @@ public:
         /*
          * Read the comment above unshare hook.
          */
-        if (unshare(CLONE_NEWNS) == -1)
+        ASSERT_EXIT("preAppSpecialize", unshare(CLONE_NEWNS) != -1, return);
-        {
-            LOGE("unshare(CLONE_NEWNS) returned -1: %d (%s)", errno, strerror(errno));
-            return;
-        }
 
         /*
          * Mount the app mount namespace's root as MS_SLAVE, so every mount/umount from
          * Zygote shared pre-specialization namespace is propagated to this one.
          */
-        if (mount("rootfs", "/", NULL, (MS_SLAVE | MS_REC), NULL) == -1)
+        ASSERT_EXIT("preAppSpecialize", mount("rootfs", "/", NULL, (MS_SLAVE | MS_REC), NULL) != -1, return);
-        {
-            LOGE("mount(\"rootfs\", \"/\", NULL, (MS_SLAVE | MS_REC), NULL) returned -1: %d (%s)", errno, strerror(errno));
-            return;
-        }
 
-        if (!hookPLTByName("libandroid_runtime.so", "unshare", new_unshare, &old_unshare))
+        ASSERT_EXIT("preAppSpecialize", hookPLTByName("libandroid_runtime.so", "unshare", new_unshare, &old_unshare), return);
+
+        ASSERT_LOG("preAppSpecialize", (companionFd = api->connectCompanion()) != -1);
+
+        callbackFunction = [fd = companionFd]()
         {
-            LOGE("plt_hook_wrapper(\"libandroid_runtime.so\", \"unshare\", new_unshare, old_unshare) returned false");
+            bool result = false;
-            return;
+            if (fd != -1)
-        }
+            {
+                do
+                {
+                    pid_t pid = getpid();
+                    ASSERT_EXIT("invokeZygiskCompanion", write(fd, &pid, sizeof(pid)) == sizeof(pid), break);
+                    ASSERT_EXIT("invokeZygiskCompanion", read(fd, &result, sizeof(result)) == sizeof(result), break);
+                } while (false);
+                close(fd);
+            }
+
+            if (result)
+                LOGD("Invoking the companion was successful.");
+            else
+            {
+                LOGW("Invoking the companion failed. Performing operations in Zygote context!");
+                doUnmount();
+                doRemount();
+            }
+        };
     }
 
     void preServerSpecialize(ServerSpecializeArgs *args) override
@@ -98,10 +116,8 @@ public:
 
     void postAppSpecialize(const AppSpecializeArgs *args) override
     {
-        if (old_unshare != nullptr && !hookPLTByName("libandroid_runtime.so", "unshare", old_unshare))
+        if (old_unshare != nullptr)
-        {
+            ASSERT_LOG("postAppSpecialize", hookPLTByName("libandroid_runtime.so", "unshare", old_unshare));
-            LOGE("plt_hook_wrapper(\"libandroid_runtime.so\", \"unshare\", old_unshare) returned false");
-        }
     }
 
     template <typename T>
@@ -111,8 +127,30 @@ public:
     }
 
 private:
+    int companionFd = -1;
     Api *api;
     JNIEnv *env;
 };
 
+void zygisk_companion_handler(int fd)
+{
+    bool result = [&]() -> bool
+    {
+        pid_t pid;
+        ASSERT_EXIT("zygisk_companion_handler", read(fd, &pid, sizeof(pid)) == sizeof(pid), return false);
+        LOGD("zygisk_companion_handler received pid=%d", pid);
+
+        ASSERT_EXIT("zygisk_companion_handler", unshare(CLONE_NEWNS) != -1, return false);
+        ASSERT_EXIT("zygisk_companion_handler", switchMountNS(pid), return false);
+
+        doUnmount();
+        doRemount();
+
+        return true;
+    }();
+
+    ASSERT_LOG("zygisk_companion_handler", write(fd, &result, sizeof(result)) == sizeof(result));
+}
+
 REGISTER_ZYGISK_MODULE(ZygiskModule)
+REGISTER_ZYGISK_COMPANION(zygisk_companion_handler)

module/jni/mount_parser.cpp

@@ -7,6 +7,7 @@
 
 #include "mount_parser.hpp"
 #include "logging.hpp"
+#include "utils.hpp"
 
 mount_entry_t::mount_entry_t(::mntent *entry)
     : fsname(entry->mnt_fsname), dir(entry->mnt_dir), type(entry->mnt_type), freq(entry->mnt_freq), passno(entry->mnt_passno)
@@ -25,12 +26,8 @@ std::vector<mount_entry_t> parseMountsFromPath(const char *path)
 {
     std::vector<mount_entry_t> result;
 
-    FILE *file = setmntent(path, "r");
+    FILE *file;
-    if (file == NULL)
+    ASSERT_EXIT("parseMountsFromPath", (file = setmntent(path, "r")) != NULL, return result);
-    {
-        LOGE("setmntent(\"%s\", \"r\") returned NULL: %d (%s)", path, errno, strerror(errno));
-        return result;
-    }
 
     struct mntent *entry;
     while ((entry = getmntent(file)) != NULL)

module/jni/unmount.cpp

@@ -8,6 +8,7 @@
 #include "logging.hpp"
 #include "mount_parser.hpp"
 #include "mountinfo_parser.hpp"
+#include "utils.hpp"
 
 constexpr std::array<const char *, 4> fsname_list = {"KSU", "APatch", "magisk", "worker"};
 
@@ -91,7 +92,7 @@ void doUnmount()
         }
         else
         {
-            LOGE("umount2(\"%s\", MNT_DETACH) returned -1: %d (%s)", mountPoint.c_str(), errno, strerror(errno));
+            LOGW("umount2(\"%s\", MNT_DETACH) returned -1: %d (%s)", mountPoint.c_str(), errno, strerror(errno));
         }
     }
 }
@@ -108,14 +109,8 @@ void doRemount()
         // If errors=remount-ro, remount it with errors=continue
         if (options.find("errors") != options.end() && options.at("errors") == "remount-ro")
         {
-            if (mount(NULL, "/data", NULL, MS_REMOUNT, "errors=continue") == 0)
+            LOGD("Trying to remount: /data");
-            {
+            ASSERT_LOG("doRemount", mount(NULL, "/data", NULL, MS_REMOUNT, "errors=continue") == 0);
-                LOGD("mount(NULL, \"/data\", NULL, MS_REMOUNT, \"errors=continue\") returned 0");
-            }
-            else
-            {
-                LOGE("mount(NULL, \"/data\", NULL, MS_REMOUNT, \"errors=continue\") returned -1: %d (%s)", errno, strerror(errno));
-            }
         }
     }
 }

module/jni/utils.cpp

@@ -1,9 +1,14 @@
 #include <string>
+#include <format>
+#include <unistd.h>
+#include <sched.h>
+#include <fcntl.h>
 
 #include "map_parser.hpp"
 #include "utils.hpp"
 #include "android_filesystem_config.h"
 #include "zygisk.hpp"
+#include "logging.hpp"
 
 bool hookPLTByName(zygisk::Api *api, const std::string &libName, const std::string &symbolName, void *hookFunc, void **origFunc)
 {
@@ -27,3 +32,17 @@ int isUserAppUID(int uid)
         return true;
     return false;
 }
+
+bool switchMountNS(int pid)
+{
+    std::string path = std::string("/proc/") + std::to_string(pid) + "/ns/mnt";
+    int ret, fd;
+    if ((fd = open(path.c_str(), O_RDONLY)) < 0)
+    {
+        return false;
+    }
+
+    ret = setns(fd, 0);
+    close(fd);
+    return ret == 0;
+}