/NCU-Linux-Kernel

Primary LanguageC

Add System Call

Kernel 3.10.104

Members

楊佳峻
方廷宇
吳榕憲

Writeup

VM Set Up

Ubuntu 16.04.7 LTS on Virtual Box

  1. Install Necessary Packages

    sudo apt update && sudo apt install wget build-essential libncurses-dev libssl-dev libelf-dev bison flex -y

  2. Download Kernel 3.10.104 & Extract it

    wget https://mirrors.edge.kernel.org/pub/linux/kernel/v3.0/linux-3.10.104.tar.gz
    tar -xvf linux-3.10.104.tar.gz -C ~/Desktop

    -C extract to which folder

    cd ~/Desktop/linux-3.10.104/

  3. Set Up Kernel Config

    sudo make menuconfig       # eg. load config-`uname -r` and exit with save

    • You can copy current configuration from device and load it

      sudo cp /boot/config-`uname -r` .config

  4. Compile Kernel & Install

    sudo make -j5 && sudo make modules_install -j5 && sudo make install -j5

  5. Update GRUB Setting

    sudo update-grub

    Because the kernel version from 4.15.0-112 to 3.10.104, we do the following things before update-grub

    sudo nano /etc/default/grub
    1. Set GRUB_TIMEOUT=-1
    2. Comment out all items starting with GRUB_HIDDEN_TIMEOUT_

  6. Reboot the Machine

    reboot
    • Select kernel-3.10.104 in ubuntu advance option when booting

Create Your Own System Call

⚠️ Please create a folder in the kernel folder, eg. custom_syscall ⚠️

  1. Write Custom System Call and Add Them into Makefile

    # file: custom_syscall/Makefile

# custom syscall file & *.c=*.o
obj-y       := helloworld.o get_phy_addr.o get_segment.o
    # file: Makefile

# ...
core-y      += kernel/ mm/ fs/ ipc/ security/ crypto/ block/
# custom_syscall # add below after the above line
core-y      += custom_syscall/
# ...

  2. Add Custom System Call in the Button of include/linux/syscalls.h

    // file: include/linux/syscalls.h

// ...
// custom // add at the end before `#endif`
asmlinkage int helloworld(void); // 8787
asmlinkage unsigned long sys_get_phy_addr(unsigned long vaddr); // 8788
asmlinkage unsigned long sys_get_segment(unsigned long vaddr, void *out); // 8789
#endif

  3. Add Custom System Call in the Button of arch/x86/syscalls/syscall_32.tbl(32 bits)

    # file: arch/x86/syscalls/syscall_32.tbl

# ...
# custom # add at the end
8787 i386   helloworld      sys_helloworld
8788 i386   get_phy_addr    sys_get_phy_addr
8789 i386   get_segment     sys_get_segment

  4. Re-compile & Re-install Kernel

Compile and Use Your System Calls

Pre-require

If your are on amd64 installation, please

sudo apt install libc6-dev-i386 -y

StackExchange Link

Use Your System Call

  1. Use your system call and get return value by using function syscall(syscall_index, arg...)

  2. Compile your .c/.cpp files using

    gcc -m32 project1.c -o project1 -lpthread -Wall -fPIE

  3. To see printk() message, use dmesg command. Eg.

    ./test_helloworld && dmesg | tail