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46 changes: 23 additions & 23 deletions Documentation/teaching/lectures/intro.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -43,9 +43,9 @@ User vs Kernel


Kernel and user are two terms that are often used in operating
systems. Their definition is pretty straight forward: The kernel is
systems. Their definition is pretty straightforward: The kernel is
the part of the operating system that runs with higher privileges
while user (space) usually means by applications running with low
while user (space) usually means applications running with low
privileges.

However these terms are heavily overloaded and might have very
Expand All @@ -55,7 +55,7 @@ User mode and kernel mode are terms that may refer specifically to the
processor execution mode. Code that runs in kernel mode can fully
[#hypervisor]_ control the CPU while code that runs in user mode has
certain limitations. For example, local CPU interrupts can only be
disabled or enable while running in kernel mode. If such an operation
disabled or enabled while running in kernel mode. If such an operation
is attempted while running in user mode an exception will be generated
and the kernel will take over to handle it.

Expand All @@ -70,8 +70,8 @@ kernel or user applications.

Grossly simplifying, the kernel space is the memory area that is
reserved to the kernel while user space is the memory area reserved to
a particular user process. The kernel space is accessed protected so
that user applications can not access it directly, while user space
a particular user process. The kernel space is access protected so
that user applications cannot access it directly, while user space
can be directly accessed from code running in kernel mode.


Expand Down Expand Up @@ -119,7 +119,7 @@ changed. Linux particularly enforces this (as opposed to in kernel
APIs that can change as needed).

The kernel code itself can be logically separated in core kernel
code and device drivers code. Device drivers code is responsible of
code and device drivers code. Device drivers code is responsible for
accessing particular devices while the core kernel code is
generic. The core kernel can be further divided into multiple logical
subsystems (e.g. file access, networking, process management, etc.)
Expand Down Expand Up @@ -174,7 +174,7 @@ directly called between various subsystems.

However, most monolithic kernels do enforce a logical separation
between subsystems especially between the core kernel and device
drivers with relatively strict APIs (but not necessarily fixed in
drivers, with relatively strict APIs (but not necessarily fixed in
stone) that must be used to access services offered by one subsystem
or device drivers. This, of course, depends on the particular kernel
implementation and the kernel's architecture.
Expand All @@ -184,10 +184,10 @@ Micro kernel
------------

A micro-kernel is one where large parts of the kernel are protected
from each-other, usually running as services in user space. Because
from eachother, usually running as services in user space. Because
significant parts of the kernel are now running in user mode, the
remaining code that runs in kernel mode is significantly smaller, hence
micro-kernel term.
the term micro-kernel.

.. slide:: Micro-kernel
:level: 2
Expand Down Expand Up @@ -220,7 +220,7 @@ micro-kernel term.

In a micro-kernel architecture the kernel contains just enough code
that allows for message passing between different running
processes. Practically that means implement the scheduler and an IPC
processes. Practically that means implementing the scheduler and an IPC
mechanism in the kernel, as well as basic memory management to setup
the protection between applications and services.

Expand All @@ -245,7 +245,7 @@ performance penalty [#minix-vs-linux]_.
Micro-kernels vs monolithic kernels
-----------------------------------

Advocates of micro-kernels often suggest that micro-kernel are
Advocates of micro-kernels often suggest that micro-kernels are
superior because of the modular design a micro-kernel
enforces. However, monolithic kernels can also be modular and there
are several approaches that modern monolithic kernels use toward this
Expand All @@ -255,7 +255,7 @@ goal:
:level: 2
:inline-contents: True

* Components can enabled or disabled at compile time
* Components can be enabled or disabled at compile time

* Support of loadable kernel modules (at runtime)

Expand All @@ -269,7 +269,7 @@ There is a class of operating systems that (used to) claim to be
hybrid kernels, in between monolithic and micro-kernels (e.g. Windows,
Mac OS X). However, since all of the typical monolithic services run
in kernel-mode in these operating systems, there is little merit to
qualify them other then monolithic kernels.
qualify them other than monolithic kernels.

.. slide:: "Hybrid" kernels
:level: 2
Expand Down Expand Up @@ -683,8 +683,8 @@ maintainers have a -next tree where they accept new features from
developers or maintainers downstream while even when the merge window
is closed.

Note that bug fixes are accepted even outside merge window in the
maintainer's tree from where they are periodically pulled by the
Note that bug fixes are accepted even outside merge window, in the
maintainer's tree, from where they are periodically pulled by the
upstream maintainer regularly, for every release candidate.


Expand Down Expand Up @@ -768,7 +768,7 @@ These are the top level of the Linux source code folders:
initialization code that runs during boot

* ipc - implementation for various Inter Process Communication system
calls such as message queue, semaphores, shared memory
calls such as message queues, semaphores, shared memory

* kernel - process management code (including support for kernel
thread, workqueues), scheduler, tracing, time management, generic
Expand All @@ -778,7 +778,7 @@ These are the top level of the Linux source code folders:
compression and decompression, bitmap manipulation, etc.

* mm - memory management code, for both physical and virtual memory,
including the page, SL*B and CMA allocators, swapping, virtual memory
including the page, SL*B, and CMA allocators, swapping, virtual memory
mapping, process address space manipulation, etc.

* net - implementation for various network stacks including IPv4 and
Expand All @@ -787,7 +787,7 @@ These are the top level of the Linux source code folders:

* samples - various driver samples

* scripts - parts the build system, scripts used for building modules,
* scripts - parts of the build system, scripts used for building modules,
kconfig the Linux kernel configurator, as well as various other
scripts (e.g. checkpatch.pl that checks if a patch is conform with
the Linux kernel coding style)
Expand All @@ -803,7 +803,7 @@ These are the top level of the Linux source code folders:
* tools - various user space tools for testing or interacting with
Linux kernel subsystems

* usr - support for embedding an initrd file in the kernel image
* usr - support embedding an initrd file in the kernel image

* virt - home of the KVM (Kernel Virtual Machine) hypervisor

Expand Down Expand Up @@ -912,7 +912,7 @@ Device drivers

* Each subsystem has its own specific driver interfaces

* Many device driver types (TTY, serial, SCSI, fileystem, ethernet,
* Many types of device drivers (TTY, serial, SCSI, filesystem, ethernet,
USB, framebuffer, input, sound, etc.)

The Linux kernel uses a unified device model whose purpose is to
Expand All @@ -928,7 +928,7 @@ to the devices it represents in order to make it easier to write
correct drivers and to reduce code duplication.

Linux supports one of the most diverse set of device drivers type,
some examples are: TTY, serial, SCSI, fileystem, ethernet, USB,
some examples are: TTY, serial, SCSI, filesystem, ethernet, USB,
framebuffer, input, sound, etc.


Expand All @@ -952,7 +952,7 @@ Linux implements the standard Unix process management APIs such as
fork(), exec(), wait(), as well as standard POSIX threads.

However, Linux processes and threads are implemented particularly
different than other kernels. There are no internal structures
differently than other kernels. There are no internal structures
implementing processes or threads, instead there is a :c:type:`struct
task_struct` that describe an abstract scheduling unit called task.

Expand Down Expand Up @@ -1157,7 +1157,7 @@ Linux Security Modules

* Used by several Linux security extensions:

* Security Enhancened Linux
* Security Enhanced Linux

* AppArmor

Expand Down