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| author | Frans Kaashoek <[email protected]> | 2019-08-20 20:23:18 -0400 |
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| committer | Frans Kaashoek <[email protected]> | 2019-08-20 20:23:18 -0400 |
| commit | 7241838b4cecefb32bad4698e748fc31d008d94d (patch) | |
| tree | 7b52f0c55604ee8801d2a6edfe46c4d931e35273 /labs/xv6.html | |
| parent | c612d452fdb03080c77517f6c1b32b8d11c6c40a (diff) | |
| download | xv6-labs-7241838b4cecefb32bad4698e748fc31d008d94d.tar.gz xv6-labs-7241838b4cecefb32bad4698e748fc31d008d94d.tar.bz2 xv6-labs-7241838b4cecefb32bad4698e748fc31d008d94d.zip | |
Move labs into 6.828 repo. The lab text isn't dependent on specific
xv6 code. Lab submission instructions etc. are likely going to be more
MIT 6.828 specific.
Diffstat (limited to 'labs/xv6.html')
| -rw-r--r-- | labs/xv6.html | 238 |
1 files changed, 0 insertions, 238 deletions
diff --git a/labs/xv6.html b/labs/xv6.html deleted file mode 100644 index 13d581e..0000000 --- a/labs/xv6.html +++ /dev/null @@ -1,238 +0,0 @@ -<html> -<head> -<title>Lab: xv6</title> -<link rel="stylesheet" href="homework.css" type="text/css" /> -</head> -<body> - -<h1>Lab: xv6</h1> - -This lab makes you familiar with xv6 and its system calls. - -<h2>Boot xv6</h2> - -<p>Login to Athena (e.g., ssh -X athena.dialup.mit.edu) and attach the course -locker: (You must run this command every time you log in; or add it to your -~/.environment file.) - -<pre> -$ add -f 6.828 -</pre> - -<p>Fetch the xv6 source: - -<pre> -$ mkdir 6.828 -$ cd 6.828 -$ git clone git://github.com/mit-pdos/xv6-riscv.git -Cloning into 'xv6-riscv'... -... -$ -</pre> - -<p>XXX pointer to an update tools page - -<p>Build xv6 on Athena: -<pre> -$ cd xv6-public -$ makeriscv64-linux-gnu-gcc -c -o kernel/entry.o kernel/entry.S -riscv64-linux-gnu-gcc -Wall -Werror -O -fno-omit-frame-pointer -ggdb -MD -mcmodel=medany -ffreestanding -fno-common -nostdlib -mno-relax -I. -fno-stack-protector -fno-pie -no-pie -c -o kernel/start.o kernel/start.c -... -$ make qemu -... -mkfs/mkfs fs.img README user/_cat user/_echo user/_forktest user/_grep user/_init user/_kill user/_ln user/_ls user/_mkdir user/_rm user/_sh user/_stressfs user/_usertests user/_wc user/_zombie user/_cow -nmeta 46 (boot, super, log blocks 30 inode blocks 13, bitmap blocks 1) blocks 954 total 1000 -balloc: first 497 blocks have been allocated -balloc: write bitmap block at sector 45 -qemu-system-riscv64 -machine virt -kernel kernel/kernel -m 3G -smp 3 -nographic -drive file=fs.img,if=none,format=raw,id=x0 -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0 -hart 0 starting -hart 2 starting -hart 1 starting -init: starting sh -$ -</pre> - -<p> -If you type <tt>ls</tt> at the prompt, you should output similar to the following: -<pre> -$ ls -. 1 1 1024 -.. 1 1 1024 -README 2 2 2181 -cat 2 3 21024 -echo 2 4 19776 -forktest 2 5 11456 -grep 2 6 24512 -init 2 7 20656 -kill 2 8 19856 -ln 2 9 19832 -ls 2 10 23280 -mkdir 2 11 19952 -rm 2 12 19936 -sh 2 13 38632 -stressfs 2 14 20912 -usertests 2 15 106264 -wc 2 16 22160 -zombie 2 17 19376 -cow 2 18 27152 -console 3 19 0 -</pre> -These are the programs/files that <tt>mkfs</tt> includes in the -initial file system. You just ran one of them: <tt>ls</tt>. - -<h2>sleep</h2> - -<p>Implement the UNIX program sleep for xv6; your sleep should pause - for a user-specified number of ticks. - -<p>Some hints: - <ul> - <li>Look at some of the other programs in <tt>user/</tt> to see - how you can obtain the command-line arguments passed to a program. If the user - forgets to pass an argument, sleep should print an error message. - - <li>The command-line argument is passed as a string; you can convert it to an - integer using <tt>atoi</tt> (see user/ulib.c). - - <li>Use the system call <tt>sleep</tt> (see user/usys.S and kernel/sysproc.c). - - <li>Make sure <tt>main</tt> calls <tt>exit()</tt> in order to exit - your program. - - <li>Add the program to <tt>UPROGS</tt> in Makefile and compile - user programs by typing <tt>make fs.img</tt>. - - </ul> - - <p>Run the program from the xv6 shell: - <pre> - $ make qemu - ... - init: starting sh - $ sleep 10 - (waits for a little while) - $ - </pre> - - <p>Optional: write an uptime program that prints the uptime in terms - of ticks using the <tt>uptime</tt> system call. - -<h2>pingpong</h2> - -<p> Write a program that uses UNIX system calls to ``ping-pong'' a - byte between two processes over a pair of pipes, one for each - direction. The parent sends by writing a byte to <tt>fd[1]</tt> and - the child receives it by reading from <tt>fd[0]</tt>. After - receiving a byte from parent, the child responds with its own byte - by writing to <tt>fd[1]</tt>, which the parent then reads. - -<p>Some hints: - <ul> - <li>Use <tt>pipe</tt> to create a pipe. - <li>Use <tt>fork</tt> to create a child. - <li>Use <tt>read</tt> to read from the pipe, and <tt>write</tt> to write to the pipe. - </ul> - -<h2>primes</h2> - - <p>Write a concurrent version of prime sieve using pipes. This idea - is due to Doug McIlroy, inventor of Unix pipes. The picture - halfway down <a href="http://swtch.com/~rsc/thread/">the page</a> - and the text surrounding it explain how to do it. - - <p>Your goal is to use <tt>pipe</tt> and <tt>fork</tt> to set up - the pipeline. The first process feeds the numbers 2 through 35 - into the pipeline. For each prime number, you will arrange to - create one process that reads from its left neighbor over a pipe - and writes to its right neighbor over another pipe. Since xv6 has - limited number of file descriptors and processes, the first - process can stop at 35. - -<p>Some hints: - <ul> - <li>Be careful to close file descriptors that a process doesn't - need, because otherwise your program will run xv6 out of resources - before the first process reaches 35. - - <li>Once the first process reach 35, you should arrange that the - pipeline terminates cleanly (Hint: read will return an end-of-file - when the write-side of the pipe is closed). - </ul> - -<h2>find</h2> - -<p>Write a simple version of the UNIX find program: find all the files - in a directory tree whose name matches a string. For example if the - file system contains a file <tt>a/b</tt>, then running find as - follows should produce: - <pre> - $ find . b - ./a/b - $ - </pre> - -<p>Some hints: - <ul> - <li>Look at user/ls.c to see how to read directories. - <li>Use recursion to run find in sub-directories. - <li>Don't recurse into "." and "..". - </ul> - -<p>Optional: support regular expressions in name matching. Grep has some - primitive support for regular expressions. - -<h2>xargs</h2> - -<p>Write a simple version of the UNIX xargs program: read lines from - standard in and run a command for each line, supplying the line as - arguments to the command. The following example illustrates xarg's - behavior: - <pre> - $ xargs echo bye - hello too - bye hello too - <ctrl-d> - $ - </pre> - Note that the command here is "echo bye" and the additional - arguments are "hello too", making the command "echo bye hello too", - which outputs "bye hello too". - -<p>xargs and find combine well: - <pre> - find . b | xargs grep hello - </pre> - will run "grep hello" on each file named b in the directories below ".". - -<p>Some hints: - <ul> - <li>Use <tt>fork</tt> and <tt>exec</tt> system call to invoke the - command on each line of input. Use <tt>wait</tt> in the parent - to wait for the child to complete running the command. - <li>Read from stdin a character at the time until the newline - character ('\n'). - <li>kernel/param.h declares MAXARG, which may be useful if you need - to declare an argv. - </ul> - -<h2>Optional: modify the shell</h2> - -There are endless ways in which the shell could be extended. Here are -some suggestions: - -<ul> - -<li>Modify the shell to support wait. - -<li>Modify the shell to support lists of commands, separated by ";" - -<li>Modify the shell to support sub-shells by implementing "(" and ")" - -<li>Modify the shell to allow users to edit the command line - -</ul> - -</body> -</html> - - |