OSTEP第4章 抽象：进程

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// the registers xv6 will save and restore 
// to stop and subsequently restart a process 
struct context { 
    int eip; 
    int esp; 
    int ebx; 
    int ecx; 
    int edx; 
    int esi; 
    int edi; 
    int ebp;
};
// the different states a process can be in 
enum proc_state { UNUSED, EMBRYO, SLEEPING, 
                  RUNNABLE, RUNNING, ZOMBIE };
// the information xv6 tracks about each process 
// including its register context and state 
struct proc { 
    char *mem;                  // Start of process memory
    uint sz;                    // Size of process memory
    char *kstack;               // Bottom of kernel stack
                                // for this process
    enum proc_state state;      // Process state
    int pid;                    // Process ID
    struct proc *parent;        // Parent 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
    struct context context;     // Switch here to run process
    struct trapframe *tf;       // Trap frame for the
                                // current interrupt
};