bd8434f4f4
Hi @tiann. Thanks for the great project, I had great fun playing around with it. This PR mainly tries to further minimize the possible delays caused by KernelSU hooking. There are 3 major changes: - Processes with 0 < UID < 2000 are blocked straight-up before going through the allow_list. I don't see any need for such processes to be interested in root, and this allows returning early before going through a more expensive lookup. If there's an expected breakage due to this change, I'll remove it. Let me know. - A page-sized (4K) bitmap is added. This allows O(1) lookup for UID <= 32767. This speeds up `ksu_is_allow_uid()` by about 4.8x by sacrificing a 4K memory. IMHO, a good trade-off. Most notably, this reduces the 99.999% result previously from worrying milliseconds scale to microseconds scale. For UID > 32767, another page-sized (4K) sequential array is used to cache allow_list. Compared to the previous PR #557, this new approach gives another nice 25% performance boost in average, 63-96% boost in worst cases. Benchmark results are available at https://docs.google.com/spreadsheets/d/1w_tO1zRLPNMFRer49pL1TQfL6ndEhilRrDU1XFIcWXY/edit?usp=sharing Thanks! --------- Signed-off-by: Juhyung Park <qkrwngud825@gmail.com>
252 lines
8.5 KiB
Markdown
252 lines
8.5 KiB
Markdown
# How to integrate KernelSU for non GKI kernel?
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KernelSU can be integrate to non GKI kernel, and it is backported to 4.14 now, it is also possible to run on kernel below 4.14.
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Since the fragmentization of non GKI kernels, we don't 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.
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First, you should be able to build a bootable kernel from kernel source code, if the kernel is not open sourced, then it is difficult to run KernelSU for your device.
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If you can build a bootable kernel, there are two ways to integrate KernelSU to the kernel source code:
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1. Automatically with `kprobe`
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2. Manully
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## Integrate with kprobe
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KernelSU use kprobe to do kernel hooks, if the *kprobe* runs well in your kernel, it is recommended to use this way.
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First, add KernelSU to your kernel source tree:
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```sh
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curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -
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```
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Then, you should check if *kprobe* is enabled in your kernel config, if it is not, please add these configs to it:
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```
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CONFIG_KPROBES=y
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CONFIG_HAVE_KPROBES=y
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CONFIG_KPROBE_EVENTS=y
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```
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And build your kernel again, KernelSU should works well.
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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)
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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.
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:::tip How to check if kprobe is broken？
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comment out `ksu_enable_sucompat()` and `ksu_enable_ksud()` in `KernelSU/kernel/ksu.c`, if the device boots normally, then kprobe may be broken.
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:::
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## Manully modify the kernel source
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If kprobe can not work in your kernel (maybe a upstream bug or kernel below 4.8), then you can try this way:
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First, add KernelSU to your kernel source tree:
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- Latest tag(stable)
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```sh
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curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -
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```
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- main branch(dev)
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```sh
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curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -s main
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```
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- Select tag(Such as v0.5.2)
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```sh
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curl -LSs "https://raw.githubusercontent.com/tiann/KernelSU/main/kernel/setup.sh" | bash -s v0.5.2
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```
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Then, add KernelSU calls to the kernel source, here is a patch to refer:
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```diff
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diff --git a/fs/exec.c b/fs/exec.c
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index ac59664eaecf..bdd585e1d2cc 100644
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--- a/fs/exec.c
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+++ b/fs/exec.c
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@@ -1890,11 +1890,14 @@ static int __do_execve_file(int fd, struct filename *filename,
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return retval;
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}
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+extern bool ksu_execveat_hook __read_mostly;
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+extern int ksu_handle_execveat(int *fd, struct filename **filename_ptr, void *argv,
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+ void *envp, int *flags);
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+extern int ksu_handle_execveat_sucompat(int *fd, struct filename **filename_ptr,
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+ void *argv, void *envp, int *flags);
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static int do_execveat_common(int fd, struct filename *filename,
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struct user_arg_ptr argv,
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struct user_arg_ptr envp,
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int flags)
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{
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+ if (unlikely(ksu_execveat_hook))
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+ ksu_handle_execveat(&fd, &filename, &argv, &envp, &flags);
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+ else
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+ ksu_handle_execveat_sucompat(&fd, &filename, &argv, &envp, &flags);
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return __do_execve_file(fd, filename, argv, envp, flags, NULL);
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}
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diff --git a/fs/open.c b/fs/open.c
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index 05036d819197..965b84d486b8 100644
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--- a/fs/open.c
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+++ b/fs/open.c
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@@ -348,6 +348,8 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
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return ksys_fallocate(fd, mode, offset, len);
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}
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+extern int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
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+ int *flags);
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/*
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* access() needs to use the real uid/gid, not the effective uid/gid.
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* We do this by temporarily clearing all FS-related capabilities and
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@@ -355,6 +357,7 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
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*/
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long do_faccessat(int dfd, const char __user *filename, int mode)
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{
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+ ksu_handle_faccessat(&dfd, &filename, &mode, NULL);
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const struct cred *old_cred;
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struct cred *override_cred;
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struct path path;
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diff --git a/fs/read_write.c b/fs/read_write.c
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index 650fc7e0f3a6..55be193913b6 100644
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--- a/fs/read_write.c
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+++ b/fs/read_write.c
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@@ -434,10 +434,14 @@ ssize_t kernel_read(struct file *file, void *buf, size_t count, loff_t *pos)
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}
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EXPORT_SYMBOL(kernel_read);
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+extern bool ksu_vfs_read_hook __read_mostly;
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+extern int ksu_handle_vfs_read(struct file **file_ptr, char __user **buf_ptr,
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+ size_t *count_ptr, loff_t **pos);
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ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
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{
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ssize_t ret;
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+ if (unlikely(ksu_vfs_read_hook))
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+ ksu_handle_vfs_read(&file, &buf, &count, &pos);
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+
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if (!(file->f_mode & FMODE_READ))
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return -EBADF;
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if (!(file->f_mode & FMODE_CAN_READ))
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diff --git a/fs/stat.c b/fs/stat.c
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index 376543199b5a..82adcef03ecc 100644
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--- a/fs/stat.c
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+++ b/fs/stat.c
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@@ -148,6 +148,8 @@ int vfs_statx_fd(unsigned int fd, struct kstat *stat,
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}
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EXPORT_SYMBOL(vfs_statx_fd);
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+extern int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
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+
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/**
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* vfs_statx - Get basic and extra attributes by filename
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* @dfd: A file descriptor representing the base dir for a relative filename
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@@ -170,6 +172,7 @@ int vfs_statx(int dfd, const char __user *filename, int flags,
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int error = -EINVAL;
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unsigned int lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
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+ ksu_handle_stat(&dfd, &filename, &flags);
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if ((flags & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
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AT_EMPTY_PATH | KSTAT_QUERY_FLAGS)) != 0)
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return -EINVAL;
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```
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You should found the four functions in kernel source:
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1. do_faccessat, usually in `fs/open.c`
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2. do_execveat_common, usually in `fs/exec.c`
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3. vfs_read, usually in `fs/read_write.c`
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4. vfs_statx, usually in `fs/stat.c`
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If your kernel does not have the `vfs_statx`, use `vfs_fstatat` instead:
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```diff
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diff --git a/fs/stat.c b/fs/stat.c
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index 068fdbcc9e26..5348b7bb9db2 100644
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--- a/fs/stat.c
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+++ b/fs/stat.c
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@@ -87,6 +87,8 @@ int vfs_fstat(unsigned int fd, struct kstat *stat)
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}
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EXPORT_SYMBOL(vfs_fstat);
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+extern int ksu_handle_stat(int *dfd, const char __user **filename_user, int *flags);
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+
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int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
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int flag)
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{
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@@ -94,6 +96,8 @@ int vfs_fstatat(int dfd, const char __user *filename, struct kstat *stat,
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int error = -EINVAL;
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unsigned int lookup_flags = 0;
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+ ksu_handle_stat(&dfd, &filename, &flag);
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+
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if ((flag & ~(AT_SYMLINK_NOFOLLOW | AT_NO_AUTOMOUNT |
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AT_EMPTY_PATH)) != 0)
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goto out;
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```
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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:
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```diff
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diff --git a/fs/open.c b/fs/open.c
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index 2ff887661237..e758d7db7663 100644
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--- a/fs/open.c
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+++ b/fs/open.c
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@@ -355,6 +355,9 @@ SYSCALL_DEFINE4(fallocate, int, fd, int, mode, loff_t, offset, loff_t, len)
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return error;
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}
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+extern int ksu_handle_faccessat(int *dfd, const char __user **filename_user, int *mode,
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+ int *flags);
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+
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/*
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* access() needs to use the real uid/gid, not the effective uid/gid.
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* We do this by temporarily clearing all FS-related capabilities and
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@@ -370,6 +373,8 @@ SYSCALL_DEFINE3(faccessat, int, dfd, const char __user *, filename, int, mode)
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int res;
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unsigned int lookup_flags = LOOKUP_FOLLOW;
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+ ksu_handle_faccessat(&dfd, &filename, &mode, NULL);
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+
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if (mode & ~S_IRWXO) /* where's F_OK, X_OK, W_OK, R_OK? */
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return -EINVAL;
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```
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To enable KernelSU's builtin SafeMode, You should also modify `input_handle_event` in `drivers/input/input.c`:
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:::tip
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It is strongly recommended to enable this feature, it is very helpful for recusing from bootloop!
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:::
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```diff
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diff --git a/drivers/input/input.c b/drivers/input/input.c
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index 45306f9ef247..815091ebfca4 100755
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--- a/drivers/input/input.c
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+++ b/drivers/input/input.c
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@@ -367,10 +367,13 @@ static int input_get_disposition(struct input_dev *dev,
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return disposition;
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}
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+extern bool ksu_input_hook __read_mostly;
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+extern int ksu_handle_input_handle_event(unsigned int *type, unsigned int *code, int *value);
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+
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static void input_handle_event(struct input_dev *dev,
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unsigned int type, unsigned int code, int value)
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{
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int disposition = input_get_disposition(dev, type, code, &value);
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+
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+ if (unlikely(ksu_input_hook))
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+ ksu_handle_input_handle_event(&type, &code, &value);
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if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
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add_input_randomness(type, code, value);
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```
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Finally, build your kernel again, KernelSU should works well.
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