AIM

Add a syscall to read process info into buffer.

In order to add a self-defined syscall, here is two ways:

• Insert a module.
• Patch the kernel.

CAUTION: NO SAFETY GUARANTEED

Test it in a Virtual Machine.

|- mycall.h	# Macros and Struct Definition
|- mycall.patch	# Patch for the kernel
|- mymod.c	# Module Implementation
|- myps.c	# My version of ps/pstree commands for testing my syscall

Insert a module

Tested on ubuntu 20.04 amd64 (5.15.0-105-generic).

1. Make sure headers installed
2. Compile

$ make

# or with clangd
$ bear -- make

3. Insert module

$ sudo insmod mymod.ko MYCALL_NUM=335

4. Test with my ps/pstree command.

$ ./ps
$ ./pstree

Patch the kernel

Tested with kernel linux-5.15.157.

1. Patch (with syscall number 335 in the patch file)

$ cd /usr/src/linux/
$ sudo patch -p1 < mycall.patch

2. Build the kernel

$ sudo make -j$(nproc)

3. Install the kernel and reboot

$ sudo make modules_install install
$ reboot

4. Test with my ps/pstree command.

$ ./ps -n 335
$ ./pstree -n 335