main.c

操作系统课程设计 在minix3下实现实时进程

/* This file contains the main program of MINIX as well as its shutdown code.
 * The routine main() initializes the system and starts the ball rolling by
 * setting up the process table, interrupt vectors, and scheduling each task 
 * to run to initialize itself.
 * The routine shutdown() does the opposite and brings down MINIX. 
 *
 * The entries into this file are:
 *   main:	    	MINIX main program
 *   prepare_shutdown:	prepare to take MINIX down
 *
 * Changes:
 *   Nov 24, 2004   simplified main() with system image  (Jorrit N. Herder)
 *   Aug 20, 2004   new prepare_shutdown() and shutdown()  (Jorrit N. Herder)
 */
#include "kernel.h"
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include <a.out.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include "proc.h"

/* Prototype declarations for PRIVATE functions. */
FORWARD _PROTOTYPE( void announce, (void));	
FORWARD _PROTOTYPE( void shutdown, (timer_t *tp));

/*===========================================================================*
 *				main                                         *
 *===========================================================================*/
PUBLIC void main()
{
/* Start the ball rolling. */
  struct boot_image *ip;	/* boot image pointer */
  register struct proc *rp;	/* process pointer */
  register struct priv *sp;	/* privilege structure pointer */
  register int i, s;
  int hdrindex;			/* index to array of a.out headers */
  phys_clicks text_base;
  vir_clicks text_clicks, data_clicks;
  reg_t ktsb;			/* kernel task stack base */
  struct exec e_hdr;		/* for a copy of an a.out header */

  /* Initialize the interrupt controller. */
  intr_init(1);

  /* Clear the process table. Anounce each slot as empty and set up mappings 
   * for proc_addr() and proc_nr() macros. Do the same for the table with 
   * privilege structures for the system processes. 
   */
  for (rp = BEG_PROC_ADDR, i = -NR_TASKS; rp < END_PROC_ADDR; ++rp, ++i) {
  	rp->p_rts_flags = SLOT_FREE;		/* initialize free slot */
	rp->p_nr = i;				/* proc number from ptr */
        (pproc_addr + NR_TASKS)[i] = rp;        /* proc ptr from number */
  }
  for (sp = BEG_PRIV_ADDR, i = 0; sp < END_PRIV_ADDR; ++sp, ++i) {
	sp->s_proc_nr = NONE;			/* initialize as free */
	sp->s_id = i;				/* priv structure index */
	ppriv_addr[i] = sp;			/* priv ptr from number */
  }

  /* Set up proc table entries for processes in boot image.  The stacks of the
   * kernel tasks are initialized to an array in data space.  The stacks
   * of the servers have been added to the data segment by the monitor, so
   * the stack pointer is set to the end of the data segment.  All the
   * processes are in low memory on the 8086.  On the 386 only the kernel
   * is in low memory, the rest is loaded in extended memory.
   */

  /* Task stacks. */
  ktsb = (reg_t) t_stack;

  for (i=0; i < NR_BOOT_PROCS; ++i) {
	ip = &image[i];				/* process' attributes */
	rp = proc_addr(ip->proc_nr);		/* get process pointer */
	rp->deadline = -1L;
	rp->p_max_priority = ip->priority;	/* max scheduling priority */
	rp->p_priority = ip->priority;		/* current priority */
	rp->p_quantum_size = ip->quantum;	/* quantum size in ticks */
	rp->p_ticks_left = ip->quantum;		/* current credit */
	strncpy(rp->p_name, ip->proc_name, P_NAME_LEN); /* set process name */
	(void) get_priv(rp, (ip->flags & SYS_PROC));    /* assign structure */
	priv(rp)->s_flags = ip->flags;			/* process flags */
	priv(rp)->s_trap_mask = ip->trap_mask;		/* allowed traps */
	priv(rp)->s_call_mask = ip->call_mask;		/* kernel call mask */
	priv(rp)->s_ipc_to.chunk[0] = ip->ipc_to;	/* restrict targets */
	if (iskerneln(proc_nr(rp))) {		/* part of the kernel? */ 
		if (ip->stksize > 0) {		/* HARDWARE stack size is 0 */
			rp->p_priv->s_stack_guard = (reg_t *) ktsb;
			*rp->p_priv->s_stack_guard = STACK_GUARD;
		}
		ktsb += ip->stksize;	/* point to high end of stack */
		rp->p_reg.sp = ktsb;	/* this task's initial stack ptr */
		text_base = kinfo.code_base >> CLICK_SHIFT;
					/* processes that are in the kernel */
		hdrindex = 0;		/* all use the first a.out header */
	} else {
		hdrindex = 1 + i-NR_TASKS;	/* servers, drivers, INIT */
	}

	/* The bootstrap loader created an array of the a.out headers at
	 * absolute address 'aout'. Get one element to e_hdr.
	 */
	phys_copy(aout + hdrindex * A_MINHDR, vir2phys(&e_hdr),
						(phys_bytes) A_MINHDR);
	/* Convert addresses to clicks and build process memory map */
	text_base = e_hdr.a_syms >> CLICK_SHIFT;
	text_clicks = (e_hdr.a_text + CLICK_SIZE-1) >> CLICK_SHIFT;
	if (!(e_hdr.a_flags & A_SEP)) text_clicks = 0;	   /* common I&D */
	data_clicks = (e_hdr.a_total + CLICK_SIZE-1) >> CLICK_SHIFT;
	rp->p_memmap[T].mem_phys = text_base;
	rp->p_memmap[T].mem_len  = text_clicks;
	rp->p_memmap[D].mem_phys = text_base + text_clicks;
	rp->p_memmap[D].mem_len  = data_clicks;
	rp->p_memmap[S].mem_phys = text_base + text_clicks + data_clicks;
	rp->p_memmap[S].mem_vir  = data_clicks;	/* empty - stack is in data */

	/* Set initial register values.  The processor status word for tasks 
	 * is different from that of other processes because tasks can
	 * access I/O; this is not allowed to less-privileged processes 
	 */
	rp->p_reg.pc = (reg_t) ip->initial_pc;
	rp->p_reg.psw = (iskernelp(rp)) ? INIT_TASK_PSW : INIT_PSW;

	/* Initialize the server stack pointer. Take it down one word
	 * to give crtso.s something to use as "argc".
	 */
	if (isusern(proc_nr(rp))) {		/* user-space process? */ 
		rp->p_reg.sp = (rp->p_memmap[S].mem_vir +
				rp->p_memmap[S].mem_len) << CLICK_SHIFT;
		rp->p_reg.sp -= sizeof(reg_t);
	}
	
	/* Set ready. The HARDWARE task is never ready. */
	if (rp->p_nr != HARDWARE) {
		rp->p_rts_flags = 0;		/* runnable if no flags */
		lock_enqueue(rp);		/* add to scheduling queues */
	} else {
		rp->p_rts_flags = NO_MAP;	/* prevent from running */
	}

	/* Code and data segments must be allocated in protected mode. */
	alloc_segments(rp);
  }

#if ENABLE_BOOTDEV 
  /* Expect an image of the boot device to be loaded into memory as well. 
   * The boot device is the last module that is loaded into memory, and, 
   * for example, can contain the root FS (useful for embedded systems). 
   */
  hdrindex ++;
  phys_copy(aout + hdrindex * A_MINHDR,vir2phys(&e_hdr),(phys_bytes) A_MINHDR);
  if (e_hdr.a_flags & A_IMG) {
  	kinfo.bootdev_base = e_hdr.a_syms; 
  	kinfo.bootdev_size = e_hdr.a_data; 
  }
#endif

  /* MINIX is now ready. All boot image processes are on the ready queue.
   * Return to the assembly code to start running the current process. 
   */
  bill_ptr = proc_addr(IDLE);		/* it has to point somewhere */
  announce();				/* print MINIX startup banner */
  restart();
}

/*===========================================================================*
 *				announce				     *
 *===========================================================================*/
PRIVATE void announce(void)
{
  /* Display the MINIX startup banner. */
  kprintf("\nMINIX %s.%s. "
      "Copyright 2006, Vrije Universiteit, Amsterdam, The Netherlands\n",
      OS_RELEASE, OS_VERSION);
#if (CHIP == INTEL)
  /* Real mode, or 16/32-bit protected mode? */
  kprintf("Executing in %s mode.\n\n",
      machine.protected ? "32-bit protected" : "real");
#endif
}

/*===========================================================================*
 *				prepare_shutdown			     *
 *===========================================================================*/
PUBLIC void prepare_shutdown(how)
int how;
{
/* This function prepares to shutdown MINIX. */
  static timer_t shutdown_timer;
  register struct proc *rp; 
  message m;

  /* Send a signal to all system processes that are still alive to inform 
   * them that the MINIX kernel is shutting down. A proper shutdown sequence
   * should be implemented by a user-space server. This mechanism is useful
   * as a backup in case of system panics, so that system processes can still
   * run their shutdown code, e.g, to synchronize the FS or to let the TTY
   * switch to the first console. 
   */
  kprintf("Sending SIGKSTOP to system processes ...\n"); 
  for (rp=BEG_PROC_ADDR; rp<END_PROC_ADDR; rp++) {
      if (!isemptyp(rp) && (priv(rp)->s_flags & SYS_PROC) && !iskernelp(rp))
          send_sig(proc_nr(rp), SIGKSTOP);
  }

  /* Continue after 1 second, to give processes a chance to get scheduled to 
   * do shutdown work.  Set a watchog timer to call shutdown(). The timer 
   * argument passes the shutdown status. 
   */
  kprintf("MINIX will now be shut down ...\n");
  tmr_arg(&shutdown_timer)->ta_int = how;
  shutdown(&shutdown_timer);
}
/*===========================================================================*
 *				shutdown 				     *
 *===========================================================================*/
PRIVATE void shutdown(tp)
timer_t *tp;
{
/* This function is called from prepare_shutdown or stop_sequence to bring 
 * down MINIX. How to shutdown is in the argument: RBT_HALT (return to the
 * monitor), RBT_MONITOR (execute given code), RBT_RESET (hard reset). 
 */
  int how = tmr_arg(tp)->ta_int;
  u16_t magic; 

  /* Now mask all interrupts, including the clock, and stop the clock. */
  outb(INT_CTLMASK, ~0); 
  clock_stop();

  if (mon_return && how != RBT_RESET) {
	/* Reinitialize the interrupt controllers to the BIOS defaults. */
	intr_init(0);
	outb(INT_CTLMASK, 0);
	outb(INT2_CTLMASK, 0);

	/* Return to the boot monitor. Set the program if not already done. */
	if (how != RBT_MONITOR) phys_copy(vir2phys(""), kinfo.params_base, 1); 
	level0(monitor);
  }

  /* Reset the system by jumping to the reset address (real mode), or by
   * forcing a processor shutdown (protected mode). First stop the BIOS 
   * memory test by setting a soft reset flag. 
   */
  magic = STOP_MEM_CHECK;
  phys_copy(vir2phys(&magic), SOFT_RESET_FLAG_ADDR, SOFT_RESET_FLAG_SIZE);
  level0(reset);
}