Operating System - Case Study - MINIX Notes, Study notes of Operating Systems

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Case Study : Minix

• (^) Basics of OS is already discussed:
  • (^) Processor Management
  • (^) Memory Management
  • (^) File Management
  • (^) Disk Management
• (^) Lets apply all this with Minix.

The Internal Structure of MINIX 3

• (^) MINIX 3 is structured in four layers, with each layer performing a well-defined function.

Assembly Language in Minix

• (^) Minix is primarily written in C.
  • (^) But some assembly language code is also there.

Assembly Language in Minix

• (^) The assembly language parts deal with
  • (^) interrupt handling,
  • (^) the low-level mechanics of managing context switches between processes (saving and restoring registers and the like),
  • (^) and low-level parts of manipulating the MMU hardware.

Limitations of User Layer

• (^) Layers are divided into 2 groups;
  • (^) Kernel Layer
  • (^) User Process, Server Process and Device Drivers
• (^) Layers other than kernel is limited to user mode instructions, and each is scheduled to run by the kernel.
• (^) None of them can access I/O ports directly. Furthermore, none of them can access memory outside the segments allotted to it.

File System Server

• (^) The file system (FS) carries out all the file system calls, such as - (^) read, - (^) mount, - (^) and chdir.

Kernel calls

• (^) Kernel calls are low-level functions provided by the system task to allow the drivers and servers to do their work.
• (^) Reading a hardware I/O port is a typical kernel call.

Posix Calls

• (^) In contrast, the POSIX system calls such as read, fork, and unlink are high-level calls defined by the POSIX standard, and are available to user programs in layer 4.
• (^) User programs contain many POSIX calls but no kernel calls.

Overview of System Task (1)

The message types accepted by the system task.

Overview of System Task (2)

“Any” means any system process; user processes cannot call the system task directly

Information server (IS)

• (^) The information server (IS) handles jobs such as providing debugging and status information about drivers and servers.

• The Internal Structure of MINIX
• The Internal Structure of MINIX
• The Internal Structure of MINIX
• The Internal Structure of MINIX
• The Internal Structure of MINIX