How to Change Linux Kernel Entry Point (Easy Guide for Beginners)

So, I wanted to mess around with the Linux kernel a bit, specifically, I wanted to change the entry point, you know, where the whole thing kicks off.

First, I dug into the boot process. I mean, how does the computer even know where to start running the kernel code? Turns out, it’s the bootloader, like GRUB, that loads the kernel into memory and then jumps to a specific address. This address is the entry point I was after.

I grabbed the kernel source code from my distro’s repository. It was a massive chunk of C code, pretty intimidating at first glance. I spent some time poking around, trying to get a feel for the overall structure.

Next, I needed to find where this entry point was defined. I started grepping around for keywords like “start_kernel”, “entry”, and similar stuff, It was referenced in some make files. After a bit of searching, I found out that some scripts was used to set or change saved entry.

Then came the tricky part, actually changing the entry point. I figured I couldn’t just change it to any random location, it had to be somewhere sensible, another function that did some initial setup. I picked a function that seemed to initialize some basic stuff, made a note of its address.

• Edit the Linker Script: I had to dive into the linker script.
• Recompile the Kernel: After changing the linker script, I needed to recompile the whole thing.
• Update the Bootloader: Finally, I needed to update the bootloader configuration to point to the newly compiled kernel.

I rebooted the system, fingers crossed. And guess what? It booted up! I checked the system logs and ran some basic tests to make sure everything was working as expected. There were a few hiccups, I mean, it is a big change, after all. I did some more digging and figured out that I messed up a few things during the initial setup, but I managed to iron out those wrinkles.

So yeah, I successfully changed the Linux kernel entry point. It was a pretty wild ride, lots of trial and error, but I learned a ton about how the kernel boots up and how the different pieces fit together. It’s definitely not something I’d recommend doing on a production system, but it was a fun experiment!