kernel – Page 2 – Tarik Billa

What is the “current” in Linux kernel source?

September 22, 2023 by Tarik

It’s a pointer to the current process (i.e. the process that issued the system call). On x86, it’s defined in arch/x86/include/asm/current.h (similar files for other archs). #ifndef _ASM_X86_CURRENT_H #define _ASM_X86_CURRENT_H #include <linux/compiler.h> #include <asm/percpu.h> #ifndef __ASSEMBLY__ struct task_struct; DECLARE_PER_CPU(struct task_struct *, current_task); static __always_inline struct task_struct *get_current(void) { return percpu_read_stable(current_task); } #define current get_current() #endif … Read more

How to speed up Linux kernel compilation?

September 21, 2023 by Tarik

Do not do make menuconfig for every change you make to the sources, because it will trigger a full compilation of everything, no matter how trivial your change is. This is only needed when the configuration option of the kernel changes, and that should sheldom happen during your development. Just do: make or if you … Read more

What changes in a jailbroken kernel?

September 14, 2023 by Tarik

All the “modern” kernel patches are based on comex’s patches. the main things which are being patched are: security.mac.proc_enforce cs_enforcement_disable (kernel and AMFI) PE_i_can_has_debugger vm_map_enter vm_map_protect … Oh, and there are sandbox patches too. If you wanna read more about all these patches I suggest you take a look at iOS Hacker’s Handbook. Edit: I … Read more

why is u8 u16 u32 u64 used instead of unsigned int in kernel programming

September 11, 2023 by Tarik

Often when working close to the hardware or when trying to control the size/format of a data structure you need to have precise control of the size of your integers. As for u8 vs uint8_t, this is simply because Linux predated <stdint.h> being available in C, which is technically a C99-ism, but in my experience … Read more

Learning kernel hacking and embedded development at home? [closed]

September 1, 2023 by Tarik

If you are completely new to kernel development, i would suggest not starting with hardware development and going to some “software-only” kernel modules like proc file / sysfs or for more complex examples filesystem / network development , developing on a uml/vmware/virtualbox/… machine so crashing your machine won’t hurt so much 🙂 For embedded development … Read more

How can I display the version of my Jupyter notebook and run cells in Jupyter notebooks? I get an error: bad interpreter

August 27, 2023 by Tarik

From your terminal, you can simply do: jupyter –version Or, if you are using a notebook then do: !jupyter –version Here is the output in my case: jupyter core : 4.5.0 jupyter-notebook : 5.2.2 qtconsole : 4.5.2 ipython : 5.5.0 ipykernel : 4.10.1 jupyter client : 5.3.1 jupyter lab : not installed nbconvert : 5.5.0 … Read more

When should I write a Linux kernel module?

August 24, 2023 by Tarik

Rule of thumb: try your absolute best to keep your code in user-space. If you don’t think you can, spend as much time researching alternatives to kernel code as you would writing the code (ie: a long time), and then try again to implement it in user-space. If you still can’t, research more to ensure … Read more

How / Where to find Linux Kernel Bugs to Fix?

August 17, 2023 by Tarik

1. Yes, you are right, one of the places to look is the kernel bug tracker. Searching the Linux kernel mailing list as well as the subsystem-related mailing lists could also be helpful but is probably more difficult. 2. The main kernel mailing list is here. You can find subscription instructions there. 3. There is … Read more

What parts of Linux kernel can I read for fun? [closed]

August 15, 2023 by Tarik

I would recommend looking at LXR. It makes it easier to follow the flow of the code (you do not have to search for each function that is called — well, you have, but the site does it for you). Some starting points, for the current version (2.6.30): start_kernel() — think of it as the … Read more

Mac OS X virtual audio driver

July 31, 2023 by Tarik

Take a look at the open-source WavTap, which is a simplified fork of the open-source SoundFlower virtual sound card driver. It is a .kext that I believe does substantially what you want. For reference, here is how some popular commercial closed-source options work: Rogue Amoeba’s Audio Hijack Pro -Captures system audio via code based off … Read more