All remaining assignments for this class are based on the creation and extension of a user-space device driver for a remotely connected cloud device called a Lion Cloud device.

INSTRUCTIONS TO CANDIDATES

ANSWER ALL QUESTIONS

LionCloud (v1.0)

 

All remaining assignments for this class are based on the creation and extension of a user-space

device driver for a remotely connected cloud device (called a Lion Cloud device). The vast majority

of code you will write and debug will be to provide a filesystem interface on top of the virtual

device (which is provided). At the highest level, you will translate file system commands into device

operations (see IC device interface specification below). The file system commands include open,

read, write , seek, dose and shutdown for files that are written to your file system driver. These

operations perform the same function with essentially the same arguments as the normal UNIX

I/O operations, with the caveat that they direct file contents to the LC storage device instead of the

local host/OS filesystem.

Note: This assignment description provides an overview of the assignment. The associated slides

(and in class presentation) provide more information, hints, and guidance for the project. Please

refer to those materials as well in completing this assignment.

System and Project Overview

You are to write a basic device driver that will sit between a virtual application and virtualized

hardware devices. The application makes use of the abstraction you will provide called the

LionCloud driver. The design of the system is shown in the figure here:

The LionCloud device is a software simulation of a storage device. It has a basic protocol by which

you communicate with it through a series of registers and data transfer region. You will

communicate with this device and place and get data in form of blocks. You will provide all the code

to talk to these devices and implement a simple flat filesystem (no directories).

Described in detail below, we can see three layers. The icloud_sim application is provided to you

and will call your device driver functions with the basic UNIX file operations (open, read, ...). You

are to write the device driver code to implement the file OS operations. Your code will

communicate with a virtual devices by setting registers and passing data through a virtual bus that

connects to one more more virtual cloud devices.

All of the code for application (called the simulator) and the virtual LionCloud devices is given to

you. Numerous utility functions are also provided to help debug and test your program, as well as

create readable output. A sample workload has been generated and will be used to extensively test

the program. Students that make use of all of these tools (which take a bit of time up front to figure

out) will find that the later assignments will become much easier to complete.

The LionCloud Filesystem (Icloud)

You are to write the driver that will implement the the basic UNIX file interface using the memory

system. You will write code to implement the filesystem, and make several design decisions that

will determine the structure and performance of the driver. In essence you will write code for the

read, write, open, close and other high level filesystem functions. Each function will translate the

call into low-level operations on the device (see below).

The functions you will implement for this assignment are:

. LcFHandle Lcoperi( const char ‘path ); - This function will open a file (named path, e.g.,) in the

filesystem. If the file does not exist, it should be created and set to zero length. If it does exist, it

should be opened and its read/write postion should be set to the first byte (position O). Note

that there are no subdirectories in the fllesystem, just files (so you can treat the path as a

unique filename). The function should return a unique file handle used for subsequent

operations or -1 if a failure occurs.

. mt tcctose( LcFHondte fh ); - This function closes the file referenced by the file handle that

was previously open. The function should fail (and return -1) if the file handle is bad or the file

was not previously open.

•nt lcread( LcFHandle fh, char ‘buf, size_t len ); -Thisfunction should read count bytes

from the file referenced by the file handle at the current position. Note that if there are not

enough bytes left in the file, the function should read to the end of the file and return the

number of bytes read. If there are enough bytes to fulfill the read, the function should return

count . The function should fail (and return -1) if the file handle is bad or the file was not

previously open.

. tnt lcwrite( LcFHondte fh, char buf, size_t ten ); -Thefunctionshouldwrite count bytes

into the file referenced by the file handle. If the write goes beyond the end of the file the size

should be increased. The function should always return the number of bytes written, e.g.,

count . The function should fail (and return -1) if the file handle is bad or the file was not

previously open.

tnt lcseek( I.cFHandte fh, size_t off ); - The function should set the current position into

the file to toc , where O ¡s the first byte ¡n the file ( toc is an absolute position from the front of

the file). The function should fail (and return-i) if the bc is beyond the end of the file, the file

handle is bad or the file was not previously open.

tnt lcshutdown( void ); - The function should shut down the system, including powering off

the devices and closing all files.

The Lion Cloud Device Cluster (LionC loud)

You will implement your driver on top of the Lion Cloud device cluster, which is a collection of

virtual storage devices that communicate over a kind of virtual bus/network connection. You

will begin by powering on the bus, probing to find out how many devices are available (there

are a maximum of 16), then allocating space on the devices as the application creates and

writes file data to the devices. Each device is uniquely identified by is device Id (whose type is

LcDeviceld) which is discovered during the probe process. Each device has a two-level

addressing scheme, where it has a number of sectors (s) containing blocks (b); therefore each

device has sb total blocks. A block is a region of memory of IC_DEVICE_BLOCK_SIZE bytes, as

declared in the (see tcloud_controtter.h header file.

4-bits 8-bits 8-bits 8-bits 16-bits 16-bits

GOBi CO Ci C2 DO Dl

. You communicate with the devices system by sending requests and receiving responses

through a set of packed registers. These registers are set within a 64-bit value to encode the

opcode and arguments to the hardware device.

 

Attachments:

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