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Fix booting into recovery with Android 13 GKI kernels

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With Android 13 GKI kernels, the boot partition has no ramdisk, so
Magisk constructs one from scratch. In this scenario, there's no backup
init binary at /.backup/init. For normal boot, magiskinit will symlink
/init -> /system/bin/init if needed. This commit implements the same
for booting into recovery. Before, magiskinit would just exec itself
over and over again because it couldn't restore the backup init.

Signed-off-by: Andrew Gunnerson <chillermillerlong@hotmail.com>
This commit is contained in:
Andrew Gunnerson 2022-06-25 19:27:37 -04:00 committed by John Wu
parent 4874520d65
commit 1f8c063dc6
3 changed files with 18 additions and 12 deletions
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16
native/jni/init/init.cpp
View File

@ -59,6 +59,20 @@ static int dump_bin(const uint8_t *buf, size_t sz, const char *path, mode_t mode
return 0;
}
void restore_ramdisk_init() {
unlink("/init");
const char *orig_init = backup_init();
if (access(orig_init, F_OK) == 0) {
xrename(orig_init, "/init");
} else {
// If the backup init is missing, this means that the boot ramdisk
// was created from scratch, and the real init is in a separate CPIO,
// which is guaranteed to be placed at /system/bin/init.
xsymlink(INIT_PATH, "/init");
}
}
int dump_manager(const char *path, mode_t mode) {
return dump_bin(manager_xz, sizeof(manager_xz), path, mode);
}
@ -72,7 +86,7 @@ public:
using BaseInit::BaseInit;
void start() override {
LOGD("Ramdisk is recovery, abort\n");
rename(backup_init(), "/init");
restore_ramdisk_init();
rm_rf("/.backup");
exec_init();
}

2
native/jni/init/init.hpp
View File

@ -24,6 +24,7 @@ struct BootConfig {
};
#define DEFAULT_DT_DIR "/proc/device-tree/firmware/android"
#define INIT_PATH "/system/bin/init"
extern std::vector<std::string> mount_list;
@ -33,6 +34,7 @@ void load_kernel_info(BootConfig *config);
bool check_two_stage();
void setup_klog();
const char *backup_init();
void restore_ramdisk_init();
int dump_manager(const char *path, mode_t mode);
int dump_preload(const char *path, mode_t mode);

12
native/jni/init/twostage.cpp
View File

@ -8,7 +8,6 @@
using namespace std;
#define INIT_PATH "/system/bin/init"
#define REDIR_PATH "/data/magiskinit"
void FirstStageInit::prepare() {
@ -16,16 +15,7 @@ void FirstStageInit::prepare() {
xmount("tmpfs", "/data", "tmpfs", 0, "mode=755");
cp_afc("/init" /* magiskinit */, REDIR_PATH);
unlink("/init");
const char *orig_init = backup_init();
if (access(orig_init, F_OK) == 0) {
xrename(orig_init, "/init");
} else {
// If the backup init is missing, this means that the boot ramdisk
// was created from scratch, and the real init is in a separate CPIO,
// which is guaranteed to be placed at /system/bin/init.
xsymlink(INIT_PATH, "/init");
}
restore_ramdisk_init();
{
auto init = mmap_data("/init", true);