proc.h

// Segments in proc->gdt.
#define NSEGS     7

// Per-CPU state
struct cpu {
  int privilege;               // Make up for GAIA's lack of privilege control.
  uchar id;                    // Local APIC ID; index into cpus[] below
  struct context *scheduler;   // swtch() here to enter scheduler
  volatile uint started;       // Has the CPU started?
  int ncli;                    // Depth of pushcli nesting.
  int intena;                  // Were interrupts enabled before pushcli?

  // Cpu-local storage variables; see below
  struct cpu *cpu;
  struct proc *proc;           // The currently-running process.
};

extern struct cpu cpus[NCPU];
extern int ncpu;

// Per-CPU variables, holding pointers to the
// current cpu and to the current process.

extern struct cpu *cpu;
extern struct proc *proc;

// Saved registers for kernel context switches.
// Don't need to save the all registers, because the
// calling convention is that the caller has saved most of them.
// Contexts are stored at the bottom of the stack they
// describe; the stack pointer is the address of the context.
// The layout of the context matches the layout of the stack in swtch.S
// at the "Switch stacks" comment. Switch doesn't save pc explicitly,
// but it is on the stack and allocproc() manipulates it.
struct context {
  uint r28;
  uint r29;
  uint rbp;
};

enum procstate { UNUSED, EMBRYO, SLEEPING, RUNNABLE, RUNNING, ZOMBIE };

// Per-process state
struct proc {
  uint sz;                     // Size of process memory (bytes)
  pde_t* pgdir;                // Page table
  char *kstack;                // Bottom of kernel stack for this process
  enum procstate state;        // Process state
  int pid;                     // Process ID
  struct proc *parent;         // Parent process
  struct trapframe *tf;        // Trap frame for current syscall
  struct context *context;     // swtch() here to run process
  void *chan;                  // If non-zero, sleeping on chan
  int killed;                  // If non-zero, have been killed
  struct file *ofile[NOFILE];  // Open files
  struct inode *cwd;           // Current directory
  char name[16];               // Process name (debugging)
};