xv6_with_shared_memory

This was an assignment for the class of Operating Systems in DIT @ University of Athens (2017).

• Modified xv6 kernel adding shared memory & semaphores

Source Code

New files have been added and some existing code has been updated.

• shmem.c:
  • shared memory implementation
• sem.c:
  • semaphores implementation
• proc.c:
  • changed fork to copy the addresses under the KERNBASE memory (copyuvm)
  • changed exit
• vm.c:
  • changed copyuvm to copy high addresses
  • changed deallocuvm to not kfree a shared page if it is being used from another proccess
  • added some functions for mappages and unmap_addr (via walkpgdir)
• syscall.c:
  • changed argptr to accept pointers to high addresses (shared memory)
• sysproc.c:
  • added syscalls (shmget, shmrem, sem_init, sem_up, sem_down)

Build & Run

Check the instructions in the original README.

$ cd ./src/xv6
$ make
$ make qemu-nox

Test

Test xv6 with test.c and test2.c or create new workloads.

Fork

• test.c:

// We are inside QEMU running our kernel
$ test

Multiple processes

• test2.c:

// We are inside QEMU running our kernel
$ test2&;test2&;test2&

Exit

Terminate QEMU by pressing Ctrl-A X