# Add System Call to Arm64 Linux kernel with M2 Chip ## Environment - MBP with M2 chip (2023) - MacOS 13.3 (22E252) - Vmware with Ubuntu 64bit 22.04.3 arm-64 architecture ## Prepare **Download the Linux Kernel Archives** (https://www.kernel.org) **or using** ```shell wget -P ~/ https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.15.137.tar.xz ``` **Get into root mode** ```shell sudo su // or sudo -i ``` **Decompress files to /usr/src** ```shell tar -xvf linux-5.15.137.tar.xz -C /usr/src ``` **Update apt** ```shell sudo apt update && sudo apt upgrade -y ``` **Install package which can help us to build kernel** ```shell sudo apt install build-essential libncurses-dev libssl-dev libelf-dev bison flex -y ``` **Install vim** ```shell sudo apt install vim -y ``` **Clear package** ```shell sudo apt clean && sudo apt autoremove -y ``` ## Add system calls hello **Create directory** ```bash cd /usr/src/linux-5.15.137 mkdir hello cd hello ``` **Create hello.c** ```shell vim hello.c ``` **Content of hello.c** ```C #include <linux/kernel.h> #include <linux/syscalls.h> SYSCALL_DEFINE0(hello){ printk("Hello world!\n"); return 0; } ``` **Create Makefile under the same dir** ```shell vim Makefile ``` **Content of Makefile** ``` obj-y := hello.o ``` **Back to previous dir and open makefile** ```shell # 回上個目錄 cd .. # 打開此目錄下的 Makefile vim Makefile ``` **Find core-y and append the hello/ into it** ``` core-y := kernel/ certs/ mm/ fs/ ipc/ security/ crypto/ hello/ ``` **Add system call to table and note the system call number** **----------- For ARM64 -----------** /usr/src/linux-5.15.137/include/uapi/asm-generic/unistd.h ```c // add your syscall #define __NR_hello 441 __SYSCALL(__NR_hello, sys_hello) ... // modify the total number 441 -> 442 #define __NR_syscalls 442 ``` /arch/arm64/include/asm/unistd.h ```c #define __NR_compat_syscalls number+1 ``` **------------------------------------** **Add asmlinkage long sys_hello(void); to syscalls.h** ```bash # 把目錄轉回去 cd /usr/src/linux-5.15.137 vim include/linux/syscalls.h #加入一行(這行直接加在檔案的最下面就好) 註: 在vim編輯檔案的時候 可以按shift+G就會跳到最後一行 asmlinkage long sys_hello(void); ``` ## Compile Kernel **make localmodconfig** ``` make localmodconfig #這邊會跳出一大堆問你要不要裝的套件,全部按enter跳過就好 ``` **Check processor number** ```bash nproc ``` **用幾核心去編譯** ```bash make -j12 ``` **如果要重新make，請先使用** ```bash make clean make -j12 ``` **Install Kernel** ```bash sudo make modules_install -j12 sudo make install -j12 ``` **Update boot loader and rboot** ```bash sudo update-grub reboot ``` **Check kernel version** ```bash uname -r ``` ## Issues **If kernel version doesn't update** ```shell vim /etc/default/grub GRUB_TIMEOUT_STYLE: hidden -> menu GRUB_TIMEOUT: 0 -> -1 update-grub reboot ``` **Make Failed --> Modify .config** ``` can't read modules.order: No such file or directory make:*** [Makefile:1544 __modinstpre] Error2 ``` ```shell sudo vim .config CONFIG_SYSTEM_TRUSTED_KEYS = "" CONFIG_SYSTEM_REVOCATION_KEYS = "" ``` **Make modules failed --> Install dwarves** ``` .tmp_vmlinux.btf: pahole(pahole) is not available Failed to generate BTF for vmlinux Try to disable CONFIG_DEBUG_INFO_BTF make:***[Makefile:1227:vmlinux] Error1 ``` ``` shell sudo apt-get install dwarves ``` ## Ref - TA's note: https://hackmd.io/aist49C9R46-vaBIlP3LDA?view