MarcoBuster/Magisk
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Boot MagiskInit as actual system-as-root

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WIP, no customization. DO NOT USE YET!
This commit is contained in:
topjohnwu 2019-06-23 15:14:47 -07:00
parent 28cd6a75e7
commit 9ec8bc2166
5 changed files with 93 additions and 29 deletions
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2
native/jni/Android.mk
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@ -106,7 +106,7 @@ LOCAL_C_INCLUDES := \
LOCAL_SRC_FILES := \
init/init.cpp \
init/early_mount.cpp \
init/rootfs.cpp \
init/rootdir.cpp \
init/getinfo.cpp \
magiskpolicy/api.cpp \
magiskpolicy/magiskpolicy.cpp \

43
native/jni/init/early_mount.cpp
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@ -53,17 +53,20 @@ static void collect_devices() {
closedir(dir);
}
static void setup_block(const char *partname, char *block_dev) {
static void setup_block(const char *partname, char *block_dev = nullptr) {
if (dev_list.empty())
collect_devices();
for (;;) {
for (auto &dev : dev_list) {
if (strcasecmp(dev.partname, partname) == 0) {
sprintf(block_dev, "/dev/block/%s", dev.devname);
LOGD("Found %s: [%s] (%d, %d)\n", dev.partname, dev.devname, dev.major, dev.minor);
xmkdir("/dev", 0755);
xmkdir("/dev/block", 0755);
mknod(block_dev, S_IFBLK | 0600, makedev(dev.major, dev.minor));
if (block_dev) {
sprintf(block_dev, "/dev/block/%s", dev.devname);
xmkdir("/dev/block", 0755);
}
LOGD("Found %s: [%s] (%d, %d)\n", dev.partname, dev.devname, dev.major, dev.minor);
mknod(block_dev ? block_dev : "/dev/root", S_IFBLK | 0600,
makedev(dev.major, dev.minor));
return;
}
}
@ -148,6 +151,36 @@ void SARCompatInit::early_mount() {
mount_root(odm);
}
static void switch_root(const string &path) {
LOGD("Switch root to %s\n", path.data());
vector<string> mounts;
parse_mnt("/proc/mounts", [&](mntent *me) {
if (me->mnt_dir != "/"sv && me->mnt_dir != path)
mounts.emplace_back(me->mnt_dir);
return true;
});
for (auto &dir : mounts) {
auto new_path = path + dir;
mkdir(new_path.data(), 0755);
xmount(dir.data(), new_path.c_str(), nullptr, MS_MOVE, nullptr);
}
chdir(path.data());
xmount(path.data(), "/", nullptr, MS_MOVE, nullptr);
chroot(".");
}
void SARInit::early_mount() {
char partname[32];
LOGD("Early mount system_root\n");
sprintf(partname, "system%s", cmd->slot);
setup_block(partname);
xmkdir("/system_root", 0755);
if (xmount("/dev/root", "/system_root", "ext4", MS_RDONLY, nullptr))
xmount("/dev/root", "/system_root", "erofs", MS_RDONLY, nullptr);
switch_root("/system_root");
}
#define umount_root(name) \
if (mnt_##name) \
umount("/" #name);

46
native/jni/init/init.cpp
View File

@ -132,6 +132,14 @@ void LegacyInit::preset() {
rename("/.backup/init", "/init");
}
void SARInit::preset() {
full_read("/init", &self.buf, &self.sz);
LOGD("Cleaning rootfs\n");
root = open("/", O_RDONLY | O_CLOEXEC);
frm_rf(root, { "proc", "sys" });
}
void SARCompatInit::preset() {
full_read("/init", &self.buf, &self.sz);
@ -140,23 +148,19 @@ void SARCompatInit::preset() {
frm_rf(root, { "overlay", "proc", "sys" });
}
void MagiskInit::start() {
// Prevent file descriptor confusion
mknod("/null", S_IFCHR | 0666, makedev(1, 3));
int null = open("/null", O_RDWR | O_CLOEXEC);
unlink("/null");
xdup3(null, STDIN_FILENO, O_CLOEXEC);
xdup3(null, STDOUT_FILENO, O_CLOEXEC);
xdup3(null, STDERR_FILENO, O_CLOEXEC);
if (null > STDERR_FILENO)
close(null);
void RootFSInit::start() {
preset();
early_mount();
setup_rootfs();
re_exec_init();
}
void SARInit::start() {
preset();
early_mount();
re_exec_init();
}
class RecoveryInit : public BaseInit {
public:
RecoveryInit(char *argv[], cmdline *cmd) : BaseInit(argv, cmd) {};
@ -168,13 +172,12 @@ public:
}
};
class TestInit : public SARCompatInit {
class TestInit : public SARInit {
public:
TestInit(char *argv[], cmdline *cmd) : SARCompatInit(argv, cmd) {};
TestInit(char *argv[], cmdline *cmd) : SARInit(argv, cmd) {};
void start() override {
preset();
early_mount();
setup_rootfs();
cleanup();
}
};
@ -210,6 +213,16 @@ int main(int argc, char *argv[]) {
if (getpid() != 1)
return 1;
setup_klog();
// Prevent file descriptor confusion
mknod("/null", S_IFCHR | 0666, makedev(1, 3));
int null = open("/null", O_RDWR | O_CLOEXEC);
unlink("/null");
xdup3(null, STDIN_FILENO, O_CLOEXEC);
xdup3(null, STDOUT_FILENO, O_CLOEXEC);
xdup3(null, STDERR_FILENO, O_CLOEXEC);
if (null > STDERR_FILENO)
close(null);
}
cmdline cmd{};
@ -219,7 +232,10 @@ int main(int argc, char *argv[]) {
if (run_test) {
init = make_unique<TestInit>(argv, &cmd);
} else if (cmd.system_as_root) {
init = make_unique<SARCompatInit>(argv, &cmd);
if (access("/overlay", F_OK) == 0) /* Compatible mode */
init = make_unique<SARCompatInit>(argv, &cmd);
else
init = make_unique<SARInit>(argv, &cmd);
} else {
decompress_ramdisk();
if (access("/sbin/recovery", F_OK) == 0)

29
native/jni/init/init.h
View File

@ -35,29 +35,44 @@ protected:
virtual void preset() = 0;
virtual void early_mount() = 0;
void setup_rootfs();
bool read_dt_fstab(const char *name, char *partname, char *fstype);
bool patch_sepolicy();
void cleanup() override;
public:
MagiskInit(char *argv[], cmdline *cmd) : BaseInit(argv, cmd) {};
};
class SARInit : public MagiskInit {
protected:
void preset() override;
void early_mount() override;
public:
SARInit(char *argv[], cmdline *cmd) : MagiskInit(argv, cmd) {};
void start() override;
};
class LegacyInit : public MagiskInit {
class RootFSInit : public MagiskInit {
protected:
void preset() override;
void early_mount() override;
void setup_rootfs();
public:
LegacyInit(char *argv[], cmdline *cmd) : MagiskInit(argv, cmd) {};
RootFSInit(char *argv[], cmdline *cmd) : MagiskInit(argv, cmd) {};
void start() override;
};
class SARCompatInit : public MagiskInit {
class LegacyInit : public RootFSInit {
protected:
void preset() override;
void early_mount() override;
public:
SARCompatInit(char *argv[], cmdline *cmd) : MagiskInit(argv, cmd) {};
LegacyInit(char *argv[], cmdline *cmd) : RootFSInit(argv, cmd) {};
};
class SARCompatInit : public RootFSInit {
protected:
void preset() override;
void early_mount() override;
public:
SARCompatInit(char *argv[], cmdline *cmd) : RootFSInit(argv, cmd) {};
};
static inline bool is_lnk(const char *name) {

2
native/jni/init/rootfs.cpp → native/jni/init/rootdir.cpp
View File

@ -39,7 +39,7 @@ constexpr const char wrapper[] =
"exec /sbin/magisk.bin \"$0\" \"$@\"\n"
;
void MagiskInit::setup_rootfs() {
void RootFSInit::setup_rootfs() {
bool patch_init = patch_sepolicy();
if (cmd->system_as_root) {