#EMACS MACROS CODE#
Ok, what do we see here? This simple code represents Hello world assembly program for the Linux x86_64 architecture. We can compile the above with the following commands: $ gcc -c test.S Let's look on a simple Hello world example that's written in the assembly programming language. For example: the x86_64 provides 322 system calls and the x86 provides 358 different system calls. The Linux kernel provides a set of these functions and each architecture provides its own set. In other words, a system call is just a C kernel space function that user space programs call to handle some request. When your program wants to write to or read from a file, start to listen for connections on a socket, delete or create directory, or even to finish its work, a program uses a system call. Yes, the operating system kernel provides many services. What is it?Ī system call is just a userspace request of a kernel service. We will see an implementation of a couple system call handlers in the Linux kernel, VDSO and vsyscall concepts and many many more.īefore we dive into Linux system call implementation, it is good to know some theory about system calls. For example, we will learn what's happening when a system call occurs from userspace. We will see many different aspects that are related to the system call concept.
#EMACS MACROS SOFTWARE#
This is because the most common way to implement system calls is as software interrupts. The concept of system calls is very similar to that of interrupts. In the previous chapter we saw interrupts and interrupt handling. The choice of topic for this chapter is not accidental. This post opens up a new chapter in linux-insides book, and as you may understand from the title, this chapter will be devoted to the System call concept in the Linux kernel.
#EMACS MACROS PATCH#
Write and Submit your first Linux kernel Patch How the Linux kernel handles a system call Initialization of external hardware interrupts structures Implementation of some exception handlers Initialization of non-early interrupt gates Last preparations before the kernel entry pointĬontinue architecture-specific boot-time initializationsĪrchitecture-specific initializations, again.Įnd of the architecture-specific initializations, almost. ^[O3d it stands for the key combination Alt+ Left, and your bindings will work.Video mode initialization and transition to protected mode Once you've declared these translations, Emacs will know that when the terminal sends e.g. (kbd "M-") or (kbd "") are alternative ways of writing. emacs): (define-key input-decode-map "\eO3a" ) You'll see something like ^[O3d where that ^[ is not the two characters ^[ but an escape character, better written in an Emacs Lisp string as \e.Īdd each key combination's escape sequence to input-decode-map. The Ctrl+ Q command tells Emacs to interpret the leading escape character literally. Alt+ Left) to enter the key sequence in a buffer. Press Ctrl+ Q then the key combination (e.g. Unfortunately, some of these character sequences are not standardized, so you need to declare what your terminal sends to Emacs. When you press Alt+ Left, it is translated into the sequence of characters \eO3d where \e is an escape character. Terminals know characters, not keys, so keys with no corresponding character need to be translated into escape sequences and back.
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