3.1 Kernel OrganizationThe FreeBSD kernel can be viewed as a service provider to user processes. Processes usually access these services through system calls. Some services, such as process scheduling and memory management, are implemented as processes that execute in kernel mode or as routines that execute periodically within the kernel.In this chapter, we describe how kernel services are provi..

2.8 DevicesHistorically, the device interface was static and simple. Devices were discovered as the system was booted and did not change thereafter. A typical disk driver could be written in a few hundred lines of code. As the system has evolved, the complexity of the I/O system has increased, with the addition of new functionality. Devices may appear and later disappear while the system is runn..

2.6 Memory ManagementEach process has its own private address space. The address space is initially divided into three logical segments: text, data, and stack. The text segment is read-only and contains the machine instructions of a program. The data and stack segments are both readable and writable. The data segment contains the initialized and uninitialized data portions of a program, whereas ..

2.5 Security The FreeBSD security model has been developed over 40 years of evolving application needs. The key insight is that security must be part of system design; it cannot be successfully added later. The model addresses many different goals:Support authenticated local and remote access by multiple users, as well as integration with distributed authentication and directory servicesAllow us..

Kernel Services The boundary between the kernel- and user-level code is enforced by hardware-protection facilities provided by the underlying hardware. The kernel operates in a separate address space that is inaccessible to user processes. Privileged operations—such as starting I/O and halting the central processing unit (CPU)—are available to only the kernel. Applications request services from ..

The kernel     커널이란? The kernel is the part of the system that runs in protected mode and mediates access by all user programs to the underlying hardware (e.g., CPU, keyboard, monitor, disks, network links) and software constructs (e.g., filesystem, network protocols). The kernel provides the basic system facilities; it creates and manages processes and provides functions to access the filesyste..