text: /*
   *  arch/mips/mm/fault.c
   *
   *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   *  Ported to MIPS by Ralf Baechle
   */
  
  #include <linux/config.h>
  #include <linux/signal.h>
  #include <linux/sched.h>
  #include <linux/head.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/types.h>
  #include <linux/ptrace.h>
  #include <linux/mman.h>
  #include <linux/mm.h>
  
  #include <asm/system.h>
  #include <asm/segment.h>
  #include <asm/mipsconfig.h>
  
  extern void die_if_kernel(char *, struct pt_regs *, long);
  
  /*
   * This routine handles page faults.  It determines the address,
   * and the problem, and then passes it off to one of the appropriate
   * routines.
   *
   * The error_code parameter just the same as in the i386 version:
   *
   *	bit 0 == 0 means no page found, 1 means protection fault
   *	bit 1 == 0 means read, 1 means write
   *	bit 2 == 0 means kernel, 1 means user-mode
   */
  asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code)
  {
  	struct vm_area_struct * vma;
  	unsigned long address;
  	unsigned long page;
  
  	/* get the address */
  	__asm__("dmfc0\t%0,$8"
  	        : "=r" (address));
  
  	for (vma = current->mm->mmap ; ; vma = vma->vm_next) {
  		if (!vma)
  			goto bad_area;
  		if (vma->vm_end > address)
  			break;
  	}
  	if (vma->vm_start <= address)
  		goto good_area;
  	if (!(vma->vm_flags & VM_GROWSDOWN))
  		goto bad_area;
  	if (vma->vm_end - address > current->rlim[RLIMIT_STACK].rlim_cur)
  		goto bad_area;
  	vma->vm_offset -= vma->vm_start - (address & PAGE_MASK);
  	vma->vm_start = (address & PAGE_MASK);
  /*
   * Ok, we have a good vm_area for this memory access, so
   * we can handle it..
   */
  good_area:
  	/*
  	 * was it a write?
  	 */
  	if (error_code & 2) {
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  	} else {
  		/* read with protection fault? */
  		if (error_code & 1)
  			goto bad_area;
  		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  			goto bad_area;
  	}
  	if (error_code & 1) {
  		do_wp_page(vma, address, error_code & 2);
  		return;
  	}
  	do_no_page(vma, address, error_code & 2);
  	return;
  
  /*
   * Something tried to access memory that isn't in our memory map..
   * Fix it, but check if it's kernel or user first..
   */
  bad_area:
  	if (user_mode(regs)) {
  		current->tss.cp0_badvaddr = address;
  		current->tss.error_code = error_code;
  #if 0
  		current->tss.trap_no = 14;
  #endif
  		send_sig(SIGSEGV, current, 1);
  		return;
  	}
  	/*
  	 * Oops. The kernel tried to access some bad page. We'll have to
  	 * terminate things with extreme prejudice.
  	 */
  	if ((unsigned long) (address-TASK_SIZE) < PAGE_SIZE) {
  		printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
  		pg0[0] = pte_val(mk_pte(0, PAGE_SHARED));
  	} else
  		printk(KERN_ALERT "Unable to handle kernel paging request");
  	printk(" at virtual address %08lx\n",address);
  	page = current->tss.pg_dir;
  	printk(KERN_ALERT "current->tss.pg_dir = %08lx\n", page);
  	page = ((unsigned long *) page)[address >> PGDIR_SHIFT];
  	printk(KERN_ALERT "*pde = %08lx\n", page);
  	if (page & 1) {
  		page &= PAGE_MASK;
  		address &= 0x003ff000;
  		page = ((unsigned long *) page)[address >> PAGE_SHIFT];
  		printk(KERN_ALERT "*pte = %08lx\n", page);
  	}
  	die_if_kernel("Oops", regs, error_code);
  	do_exit(SIGKILL);
  }
  