How to integrate KernelSU for non GKI kernels?

KernelSU can be integrated into non GKI kernels, and was backported to 4.14 and below.

Due to the fragmentization of non GKI kernels, we do not have a uniform way to build it, so we can not provide non GKI boot images. But you can build the kernel yourself with KernelSU integrated.

First, you should be able to build a bootable kernel from kernel source code. If the kernel is not open source, then it is difficult to run KernelSU for your device.

If you can build a bootable kernel, there are two ways to integrate KernelSU to the kernel source code:

1. Automatically with kprobe
2. Manually

Integrate with kprobe

KernelSU uses kprobe to do kernel hooks, if the kprobe runs well in your kernel, it is recommended to use this way.

First, add KernelSU to your kernel source tree:

curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -

Then, you should check if kprobe is enabled in your kernel config, if it is not, please add these configs to it:

CONFIG_KPROBES=y
CONFIG_HAVE_KPROBES=y
CONFIG_KPROBE_EVENTS=y

And build your kernel again, KernelSU should works well.

If you find that KPROBES is still not activated, you can try enabling CONFIG_MODULES. (If it still doesn't take effect, use make menuconfig to search for other dependencies of KPROBES)

But if you encounter a boot loop when integrated KernelSU, it is maybe kprobe is broken in your kernel, you should fix the kprobe bug or use the second way.

How to check if kprobe is broken？

comment out ksu_enable_sucompat() and ksu_enable_ksud() in KernelSU/kernel/ksu.c, if the device boots normally, then kprobe may be broken.

How to get module umount feature working on pre-GKI?

If your kernel is older than 5.9, you should backport path_umount to fs/namespace.c. This is required to get module umount feature working. If you don't backport path_umount, module umount feature won't work. You can get more info on how to achieve this at the end of this page.

Manually modify the kernel source

If kprobe does not work in your kernel (may be an upstream or kernel bug below 4.8), then you can try this way:

First, add KernelSU to your kernel source tree:

Latest tag(stable)

curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -

main branch(dev)

curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -s main

Select tag(Such as v0.5.2)

curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -s v0.5.2

Keep in mind that on some devices, your defconfig may be in arch/arm64/configs or in other cases arch/arm64/configs/vendor/your_defconfig. For example in your defconfig, Enable CONFIG_KSU with y to enable, or n to disable. Your path will be something like: arch/arm64/configs/...

# KernelSU
CONFIG_KSU=y

Then, add KernelSU calls to the kernel source, here are some patches to refer:

exec.c

diff --git a/fs/exec.c b/fs/exec.c
index ac59664eaecf..bdd585e1d2cc 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1890,11 +1890,14 @@ static int __do_execve_file(int fd, struct filename *filename,
 	return retval;
 }

+#ifdef CONFIG_KSU
+extern bool ksu_execveat_hook __read_mostly;
+extern int ksu_handle_execveat(int *fd, struct filename **filename_ptr, void *argv,
+			void *envp, int *flags);
+extern int ksu_handle_execveat_sucompat(int *fd, struct filename **filename_ptr,
+				 void *argv, void *envp, int *flags);
+#endif
 static int do_execveat_common(int fd, struct filename *filename,
 			      struct user_arg_ptr argv,
 			      struct user_arg_ptr envp,
 			      int flags)
 {
+   #ifdef CONFIG_KSU
+	if (unlikely(ksu_execveat_hook))
+		ksu_handle_execveat(&fd, &filename, &argv, &envp, &flags);
+	else
+		ksu_handle_execveat_sucompat(&fd, &filename, &argv, &envp, &flags);
+   #endif
 	return __do_execve_file(fd, filename, argv, envp, flags, NULL);
 }

open.c

diff --git a/fs/open.c b/fs/open.c
index 05036d819197..965b84d486b8 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -348,6 +348,8 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 	return ksys_fallocate(fd, mode, offset, len);
 }

+#ifdef CONFIG_KSU
+extern int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
+			 int *flags);
+#endif
 /*
  * access() needs to use the real uid/gid, not the effective uid/gid.
  * We do this by temporarily clearing all FS-related capabilities and
@@ -355,6 +357,7 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
  */
 long do_faccessat(int dfd, const char __user *filename, int mode)
 {
 	const struct cred *old_cred;
 	struct cred *override_cred;
 	struct path path;
 	struct inode *inode;
 	struct vfsmount *mnt;
 	int res;
 	unsigned int lookup_flags = LOOKUP_FOLLOW;
+   #ifdef CONFIG_KSU
+	ksu_handle_faccessat(&dfd, &filename, &mode, NULL);
+   #endif
 
 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
 		return -EINVAL;

read_write.c

diff --git a/fs/read_write.c b/fs/read_write.c
index 650fc7e0f3a6..55be193913b6 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -434,10 +434,14 @@ ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
 }
 EXPORT_SYMBOL(kernel_read);

+#ifdef CONFIG_KSU
+extern bool ksu_vfs_read_hook __read_mostly;
+extern int ksu_handle_vfs_read(struct file **file_ptr, char __user **buf_ptr,
+			size_t *count_ptr, loff_t **pos);
+#endif
 ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
 {
 	ssize_t ret;
+   #ifdef CONFIG_KSU 
+	if (unlikely(ksu_vfs_read_hook))
+		ksu_handle_vfs_read(&file, &buf, &count, &pos);
+   #endif
+
 	if (!(file->f_mode & FMODE_READ))
 		return -EBADF;
 	if (!(file->f_mode & FMODE_CAN_READ))

stat.c

diff --git a/fs/stat.c b/fs/stat.c
index 376543199b5a..82adcef03ecc 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -148,6 +148,8 @@ int vfs_statx_fd(unsigned int fd, struct kstat *stat,
 }
 EXPORT_SYMBOL(vfs_statx_fd);

+#ifdef CONFIG_KSU
+extern int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
+#endif
+
 /**
  * vfs_statx - Get basic and extra attributes by filename
  * @dfd: A file descriptor representing the base dir for a relative filename
@@ -170,6 +172,7 @@ int vfs_statx(int dfd, const char __user *filename, int flags,
 	int error = -EINVAL;
 	unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;

+   #ifdef CONFIG_KSU
+	ksu_handle_stat(&dfd, &filename, &flags);
+   #endif
 	if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
 		       AT_EMPTY_PATH | KSTAT_QUERY_FLAGS)) != 0)
 		return -EINVAL;

You should find the four functions in kernel source:

1. do_faccessat, usually in fs/open.c
2. do_execveat_common, usually in fs/exec.c
3. vfs_read, usually in fs/read_write.c
4. vfs_statx, usually in fs/stat.c

If your kernel does not have the vfs_statx, use vfs_fstatat instead:

diff --git a/fs/stat.c b/fs/stat.c
index 068fdbcc9e26..5348b7bb9db2 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -87,6 +87,8 @@ int vfs_fstat(unsigned int fd, struct kstat *stat)
 }
 EXPORT_SYMBOL(vfs_fstat);

+#ifdef CONFIG_KSU
+extern int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
+#endif
 int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
 		int flag)
 {
@@ -94,6 +96,8 @@ int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
 	int error = -EINVAL;
 	unsigned int lookup_flags = 0;
+   #ifdef CONFIG_KSU 
+	ksu_handle_stat(&dfd, &filename, &flag);
+   #endif
+
 	if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
 		      AT_EMPTY_PATH)) != 0)
 		goto out;

For kernels eariler than 4.17, if you cannot find do_faccessat, just go to the definition of the faccessat syscall and place the call there:

diff --git a/fs/open.c b/fs/open.c
index 2ff887661237..e758d7db7663 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -355,6 +355,9 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
 	return error;
 }

+#ifdef CONFIG_KSU
+extern int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
+			        int *flags);
+#endif
+
 /*
  * access() needs to use the real uid/gid, not the effective uid/gid.
  * We do this by temporarily clearing all FS-related capabilities and
@@ -370,6 +373,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
 	int res;
 	unsigned int lookup_flags = LOOKUP_FOLLOW;
+   #ifdef CONFIG_KSU
+	ksu_handle_faccessat(&dfd, &filename, &mode, NULL);
+   #endif
+
 	if (mode & ~S_IRWXO)	/* where's F_OK, X_OK, W_OK, R_OK? */
 		return -EINVAL;

To enable KernelSU's builtin SafeMode, You should also modify input_handle_event in drivers/input/input.c:

TIP

It is strongly recommended to enable this feature, it is very helpful to prevent bootloops!

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 45306f9ef247..815091ebfca4 100755
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -367,10 +367,13 @@ static int input_get_disposition(struct input_dev *dev,
 	return disposition;
 }

+#ifdef CONFIG_KSU
+extern bool ksu_input_hook __read_mostly;
+extern int ksu_handle_input_handle_event(unsigned int *type, unsigned int *code, int *value);
+#endif
+
 static void input_handle_event(struct input_dev *dev,
 			       unsigned int type, unsigned int code, int value)
 {
	int disposition = input_get_disposition(dev, type, code, &value);
+   #ifdef CONFIG_KSU
+	if (unlikely(ksu_input_hook))
+		ksu_handle_input_handle_event(&type, &code, &value);
+   #endif
 
 	if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
 		add_input_randomness(type, code, value);

How to backport path_umount

You can get module umount feature working on pre-GKI kernels by manually backporting path_umount from 5.9. You can use this patch as reference:

--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1739,6 +1739,39 @@ static inline bool may_mandlock(void)
 }
 #endif

+static int can_umount(const struct path *path, int flags)
+{
+	struct mount *mnt = real_mount(path->mnt);
+
+	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
+		return -EINVAL;
+	if (!may_mount())
+		return -EPERM;
+	if (path->dentry != path->mnt->mnt_root)
+		return -EINVAL;
+	if (!check_mnt(mnt))
+		return -EINVAL;
+	if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
+		return -EINVAL;
+	if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+int path_umount(struct path *path, int flags)
+{
+	struct mount *mnt = real_mount(path->mnt);
+	int ret;
+
+	ret = can_umount(path, flags);
+	if (!ret)
+		ret = do_umount(mnt, flags);
+
+	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
+	dput(path->dentry);
+	mntput_no_expire(mnt);
+	return ret;
+}
 /*
  * Now umount can handle mount points as well as block devices.
  * This is important for filesystems which use unnamed block devices.

Finally, build your kernel again, KernelSU should work well.

Entering safe mode accidiently?

If you use manual integration and do not disable CONFIG_KPROBES, then the user may trigger safe mode by pressing the volume down button after booting! Therefore if using manual integration you need to disable CONFIG_KPROBES!