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.) + +
+$ add -f 6.828 ++ +
Fetch the xv6 source: + +
+$ mkdir 6.828 +$ cd 6.828 +$ git clone git://github.com/mit-pdos/xv6-riscv.git +Cloning into 'xv6-riscv'... +... +$ ++ +
XXX pointer to an update tools page + +
Build xv6 on Athena: +
+$ 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 +$ ++ +
+If you type ls at the prompt, you should output similar to the following: +
+$ 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 ++These are the programs/files that mkfs includes in the +initial file system. You just ran one of them: ls. + +
Write a program that sleeps for a user-specified number of seconds, + compile it, and run it. + +
Some hints: +
Run the program from the xv6 shell: +
+ $ make qemu + ... + init: starting sh + $ sleep 5 + (waits for a little while) + $ ++ +
Optional: write an uptime program that prints the uptime in terms + of ticks using the uptime system call. + +
In the previous exercise, if you made an error in sleep, the + program may have exited prematurely, but it didn't affect other + processes because xv6 isolates processes. Sometimes you want + processes to interact with each other. Xv6 provides two ways to do: + either through the file system (one process can create a file and + another process can read that file) or through pipes. In this + exercise you explore interprocess communication through pipes. + +
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 fd[1] and + the child receives it by reading from fd[0]. After + receiving a byte from parent, the child responds with its own byte + by writing to fd[1], which the parent then reads. + +
Some hints: +
Modify the shell to support lists of commands, separated by ";" + +
Modify the shell to support sub-shells by implementing "(" and ")" + + + + +