User space device driver implementation

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Assignment #3 - HDD Extension CMPSC311 - Introduction to Systems Programming Fall

2017- Prof. McDaniel Due date: November 17th, 2017 (11:59pm)

Overview You must start this assignment using the hdd_file_io.c code that you submitted in

assignment #2. This assignment will expand upon the previous one by saving the state of the HDD device in

a file called hdd_content.svd (you create this file from your tool). To be more precise, you’ll be able to create hdd_content.svd, which will hold all the device’s blocks. In this project, you’ll write three functions that allow for the creation, loading, and deletion of hdd_content.svd. You won’t actually be dealing with file IO directly (so no fopen or the like), but you will be using the same (and improved) functions provided last time (i.e. compare differences and look at your code comments to get started) to handle everything to do with hdd_content.svd. Continue reading for more clarity. Multiple Files

Unlike the previous assignment, you must be able to handle multiple open files at the same time. Additionally, files are no longer deleted when closed so change your hdd_close function to no longer delete a file. Thus, now hdd_close should “close” the file—meaning, once the user calls hdd_close, the seek position is reset and the user must re-open the file via hdd_open in order to then use hdd_write and hdd_read again.

Note, that in order to manage multiple files, it’s recommended you use an array of structs for your global data structure as all bytes are laid contiguously in memory (which you may find useful for other parts of this assignment). The Meta Block

The block storage now has a block that you can write to without needing a block ID: the meta block. You can create, read, and write to it just like you would any other block using hdd_data_lane except with the following changes:

• The BID within HddBitCmd should be set to 0 • The Flags within HddBitCmd should be set to HDD_META_BLOCK (i.e., a new enum for 1

defined in hdd_driver.h) The meta block should hold all the metadata about all of your files (i.e., in your global data structure). Thus, when the entire block storage is saved to hdd_content.svd, the meta block contents is saved so that when hdd_content.svd is loaded back into the device, you can retrieve the previous file system state. New Functions

Below details three new functions that YOU must implement. Note that in the previous assignment, the first function called was always hdd_open (at least, that’s the intended use of the functions as calling anything else first doesn’t make sense). However, in this assignment either

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hdd_format or hdd_mount will be called first. Thus, make sure you have an initialization check in both functions.

• [1] uint16_t hdd_format(void); o Returns 0 on success and -1 on failure o Initializes the device if not already done—this is done the same way as the previous

assignment  If initializing, then the following will happen automatically: the

hdd_content.svd file will be read and the device’s block storage will now match what was in hdd_content.svd

o Sends a format request to the device which will delete all blocks (how you do so is detailed later)

o Creates the meta block and saves your global data structure to it • [2] uint16_t hdd_mount(void);

o Returns 0 on success and -1 on failure o Initializes the device if not already done—this is done the same way as the previous

assignment  If initializing, then the following will happen automatically: the

hdd_content.svd file will be read and the device’s block storage will now match what was in hdd_content.svd.

o Reads from the meta block to populate your global data structure with previously saved values

• [3] uint16_t hdd_unmount(void); o Returns 0 on success and -1 on failure o Saves the current state of the global data structure to the meta block o Sends a save and close request to the device, which will create/update the

hdd_content.svd file (how you do so is detailed later) o Note: consider the device uninitialized after this function call

New Flags and Op Type

In order to communicate with the meta block, there’s a new flag called HDD_META_BLOCK that should be set in the HddBitCmd parameter of hdd_data_lane. In order to format the device, hdd_data_lane should also be used in which the HddBitCmd uses a new op type, HDD_DEVICE, and flag, HDD_FORMAT. Similarly, in order to save the blocks in the device to hdd_content.svd, the HDD_DEVICE op type is used and there’s a new flag, HDD_SAVE_AND_CLOSE. Below are more details:

• HDD_META_BLOCK o As mentioned previously, this flag value in HddBitCmd signifies a read or write to

the meta block • Both the HDD_FORMAT and HDD_SAVE_AND_CLOSE flags need to be used in conjunction

with the new op type, HDD_DEVICE. When the op type is HDD_DEVICE, every field besides the op field itself and the flags field should be 0. Additionally, the void data pointer (the second parameter to hdd_data_lane) can be set to NULL. Below are the details of the two flags to be used with the HDD_DEVICE op type:

o HDD_FORMAT

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 This will delete the hdd_content.svd file (if it exists) and clear the block storage of all blocks

o HDD_SAVE_AND_CLOSE  This will create the hdd_content.svd file (or overwrite it if it exists) and will

uninitialize the device

To accommodate the new flags hdd_read_block size is now defined as: int32_t hdd_read_block_size(HddBlockID bid, uint8_t flags);

This function works exactly the same way as before in assignment #2, but if you’d like to get the size of the meta block, then you provide a BID of 0 and set the flags to HDD_META_BLOCK. Getting the size of normal blocks is same except just set the flags parameter to HDD_NULL_FLAG (i.e., 0). General Compilation and Setup

1. From your virtual machine, download the starter source code provided for this assignment from CANVAS class website. Move the tgz file to your assignment directory (i.e. call it assign3). See class notes on Linux commands to do these steps.

2. Have the terminal open to the directory where the .tgz starter code file is located. Now unpackage the contents of the file: % tar xvfz assign3-starter.tgz (Remember % is a convention to represent your command line terminal, don’t type %).

3. You should be able to use the Makefile provided to build the program without modification. Thus, just compile by typing: % make clean; make

4. To get started, copy over your previous assignment’s functions (hdd_open, hdd_read,…) and any global data structures into this assignment’s hdd_file_io.c file.

5. Add appropriate English comments to your functions stating what the code is doing. All code must be correctly (and consistently) indented. Use your favorite text editor to help with this process! You will lose points if you do not comment and indent appropriately. Graders and TAs will need to understand your comments to follow your code and grade. Do not forget to add comments to the Makefile. The Makefile structure has been explained in class. On CAVAS, the Makefile book link is provided to you as a reference.

Testing (3 phases) The first phase of testing the program is performed by using the unit test function similarly

to last time (but updated to include calling the new functions). Run it by typing: ./hdd_sim -u -v

If the program completes successfully, the following should be displayed as the last log entry: HDD unit tests completed successfully.

The second phase of testing will run two workloads on your filesystem implementation. To do this, run the following commands

./hdd_sim -v workload-one.txt

./hdd_sim -v workload-two.txt If the program completes successfully, the following should be displayed as the last log entry for each workload:

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HDD simulation completed successfully. Be aware that running the first workload will produce a hdd_content.svd file that the second workload depends on. Thus, when testing, make sure you do so in the order specified here. Additionally, the next phase will depend on the hdd_content.svd file produced by workload two. In this last phase of testing, certain files loaded in the previous workloads will be extracted. Run by typing:

./hdd_sim -v -x simple.txt This should extract the file simple.txt from the device and write it to the local filesystem—meaning you’ll have a new file called simple.txt in your directory (if you want to re-run this command, delete the newly created .txt file). Next, use the diff command to compare the contents of the new file with the original version simple.txt.orig distributed with the starter code:

diff simple.txt simple.txt.orig If they are identical, diff will give no output (i.e., no differences). Repeat these commands to extract and compare the content for the files raven.txt, hamlet.txt, penn-state-alma-mater.txt, firecracker.txt, and solitude.txt.

Turn-in Instructions

1. Create a tarball file containing the assign3 directory, source code and build files. Upload the program to CANVAS by the assignment deadline (11:59pm of the day of the assignment). The tarball should be named LASTNAME-PSUEMAILID-assign3.tgz, where LASTNAME is your last name in all capital letters and PSUEMAILID is your PSU email address without the “@psu.edu”. For example, the professor was submitting a homework, he would call the file MCDANIEL-pdm12-assign3.tgz. Any file that is incorrectly named, has the incorrect directory structure, or has misnamed files, will be given a one day late penalty.

Check your structure i.e. LASTNAME-PSUEMAILID-assign3.tgz\ LASTNAME-PSUEMAILID-assign3.tar\assign3

2. Before sending the tarball, test it using the following commands (in a temporary directory – NOT the directory you used to develop the code):

% tar xvzf LASTNAME-PSUEMAILID-assign3.tgz % cd assign3 % make ... (TEST THE PROGRAM)

Note: Like all assignments in this class you are prohibited from copying any content from the Internet or discussing, sharing ideas, code, configuration, text, or anything else or getting help from anyone in or outside of the class. Consulting online sources is acceptable, but under no circumstances should anything be copied. Failure to abide by this requirement will result dismissal from the class as described in our course syllabus.