userprog

Folder structure

Here is a brief overview of the files in the userprog directory.

• exception.c
  exception.h:
  When a user process performs a privileged or prohibited operation, it traps into the kernel as an "exception" or "fault."(3) These files handle exceptions.

• gdt.c
  gdt.h:
  The 80x86 is a segmented architecture. The Global Descriptor Table (GDT) is a table that describes the segments in use. These files set up the GDT.

• pagedir.c
  pagedir.h:
  A simple manager for 80x86 hardware page tables. See section 4.1.2.3 Page Tables, for more information.

• process.c
  process.h:
  Loads ELF binaries and starts processes.

• syscall.c
  syscall.h:
  Whenever a user process wants to access some kernel functionality, it invokes a system call.

• tss.c
  tss.h:
  The Task-State Segment (TSS) is used for 80x86 architectural task switching. Pintos uses the TSS only for switching stacks when a user process enters an interrupt handler, as does Linux.

• Make.vars:
  Makefile variables specific to the userprog directory.

• Makefile:
  Makefile for building the userprog directory.