https://saurvs.github.io/ Recent content on Saurav Sachidanand Hugo -- gohugo.io en-us sauravsachidanand@gmail.com (Saurav Sachidanand) sauravsachidanand@gmail.com (Saurav Sachidanand) Thu, 02 Feb 2017 00:00:00 +0000 https://saurvs.github.io/post/writing-netbsd-kern-mod/ Thu, 02 Feb 2017 00:00:00 +0000 sauravsachidanand@gmail.com (Saurav Sachidanand) https://saurvs.github.io/post/writing-netbsd-kern-mod/ Kernel modules are object files used to extend an operating system’s kernel functionality at run time. In this post, we’ll look at implementing a simple character device driver as a kernel module in NetBSD. Once it is loaded, userspace processes will be able to write an arbitrary byte string to the device, and on every successive read expect a cryptographically-secure pseudorandom permutation of the original byte string. Before we begin, compiling a kernel module requires the NetBSD source code to live in /usr/src.