/* MN10300 MMU Fault handler
   *
   * Copyright (C) 2007 Matsushita Electric Industrial Co., Ltd.
   * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   * Modified by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #include <linux/signal.h>
  #include <linux/sched.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 <linux/smp.h>
  #include <linux/interrupt.h>
  #include <linux/init.h>
  #include <linux/vt_kern.h>		/* For unblank_screen() */
  
  #include <asm/uaccess.h>
  #include <asm/pgalloc.h>
  #include <asm/hardirq.h>
  #include <asm/cpu-regs.h>
  #include <asm/debugger.h>
  #include <asm/gdb-stub.h>
  
  /*
   * Unlock any spinlocks which will prevent us from getting the
   * message out
   */
  void bust_spinlocks(int yes)
  {
  	if (yes) {
  		oops_in_progress = 1;
  	} else {
  		int loglevel_save = console_loglevel;
  #ifdef CONFIG_VT
  		unblank_screen();
  #endif
  		oops_in_progress = 0;
  		/*
  		 * OK, the message is on the console.  Now we call printk()
  		 * without oops_in_progress set so that printk will give klogd
  		 * a poke.  Hold onto your hats...
  		 */
  		console_loglevel = 15;	/* NMI oopser may have shut the console
  					 * up */
  		printk(" ");
  		console_loglevel = loglevel_save;
  	}
  }
  
  void do_BUG(const char *file, int line)
  {
  	bust_spinlocks(1);
  	printk(KERN_EMERG "------------[ cut here ]------------
  ");
  	printk(KERN_EMERG "kernel BUG at %s:%d!
  ", file, line);
  }
  
  #if 0
  static void print_pagetable_entries(pgd_t *pgdir, unsigned long address)
  {
  	pgd_t *pgd;
  	pmd_t *pmd;
  	pte_t *pte;
  
  	pgd = pgdir + __pgd_offset(address);
  	printk(KERN_DEBUG "pgd entry %p: %016Lx
  ",
  	       pgd, (long long) pgd_val(*pgd));
  
  	if (!pgd_present(*pgd)) {
  		printk(KERN_DEBUG "... pgd not present!
  ");
  		return;
  	}
  	pmd = pmd_offset(pgd, address);
  	printk(KERN_DEBUG "pmd entry %p: %016Lx
  ",
  	       pmd, (long long)pmd_val(*pmd));
  
  	if (!pmd_present(*pmd)) {
  		printk(KERN_DEBUG "... pmd not present!
  ");
  		return;
  	}
  	pte = pte_offset(pmd, address);
  	printk(KERN_DEBUG "pte entry %p: %016Lx
  ",
  	       pte, (long long) pte_val(*pte));
  
  	if (!pte_present(*pte))
  		printk(KERN_DEBUG "... pte not present!
  ");
  }
  #endif
  
  /*
   * This routine handles page faults.  It determines the address,
   * and the problem, and then passes it off to one of the appropriate
   * routines.
   *
   * fault_code:
   * - LSW: either MMUFCR_IFC or MMUFCR_DFC as appropriate
   * - MSW: 0 if data access, 1 if instruction access
   * - bit 0: TLB miss flag
   * - bit 1: initial write
   * - bit 2: page invalid
   * - bit 3: protection violation
   * - bit 4: accessor (0=user 1=kernel)
   * - bit 5: 0=read 1=write
   * - bit 6-8: page protection spec
   * - bit 9: illegal address
   * - bit 16: 0=data 1=ins
   *
   */
  asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
  			      unsigned long address)
  {
  	struct vm_area_struct *vma;
  	struct task_struct *tsk;
  	struct mm_struct *mm;
  	unsigned long page;
  	siginfo_t info;
  	int fault;
  	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  
  #ifdef CONFIG_GDBSTUB
  	/* handle GDB stub causing a fault */
  	if (gdbstub_busy) {
  		gdbstub_exception(regs, TBR & TBR_INT_CODE);
  		return;
  	}
  #endif
  
  #if 0
  	printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)
  ",
  	       regs,
  	       fault_code & 0x10000 ? "ins" : "data",
  	       fault_code & 0xffff, address);
  #endif
  
  	tsk = current;
  
  	/*
  	 * We fault-in kernel-space virtual memory on-demand. The
  	 * 'reference' page table is init_mm.pgd.
  	 *
  	 * NOTE! We MUST NOT take any locks for this case. We may
  	 * be in an interrupt or a critical region, and should
  	 * only copy the information from the master page table,
  	 * nothing more.
  	 *
  	 * This verifies that the fault happens in kernel space
  	 * and that the fault was a page not present (invalid) error
  	 */
  	if (address >= VMALLOC_START && address < VMALLOC_END &&
  	    (fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR &&
  	    (fault_code & MMUFCR_xFC_PGINVAL) == MMUFCR_xFC_PGINVAL
  	    )
  		goto vmalloc_fault;
  
  	mm = tsk->mm;
  	info.si_code = SEGV_MAPERR;
  
  	/*
  	 * If we're in an interrupt or have no user
  	 * context, we must not take the fault..
  	 */
  	if (in_atomic() || !mm)
  		goto no_context;
  
  	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
  		flags |= FAULT_FLAG_USER;
  retry:
  	down_read(&mm->mmap_sem);
  
  	vma = find_vma(mm, address);
  	if (!vma)
  		goto bad_area;
  	if (vma->vm_start <= address)
  		goto good_area;
  	if (!(vma->vm_flags & VM_GROWSDOWN))
  		goto bad_area;
  
  	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
  		/* accessing the stack below the stack pointer is always a
  		 * bug */
  		if ((address & PAGE_MASK) + 2 * PAGE_SIZE < regs->sp) {
  #if 0
  			printk(KERN_WARNING
  			       "[%d] ### Access below stack @%lx (sp=%lx)
  ",
  			       current->pid, address, regs->sp);
  			printk(KERN_WARNING
  			       "vma [%08x - %08x]
  ",
  			       vma->vm_start, vma->vm_end);
  			show_registers(regs);
  			printk(KERN_WARNING
  			       "[%d] ### Code: [%08lx]"
  			       " %02x %02x %02x %02x %02x %02x %02x %02x
  ",
  			       current->pid,
  			       regs->pc,
  			       ((u8 *) regs->pc)[0],
  			       ((u8 *) regs->pc)[1],
  			       ((u8 *) regs->pc)[2],
  			       ((u8 *) regs->pc)[3],
  			       ((u8 *) regs->pc)[4],
  			       ((u8 *) regs->pc)[5],
  			       ((u8 *) regs->pc)[6],
  			       ((u8 *) regs->pc)[7]
  			       );
  #endif
  			goto bad_area;
  		}
  	}
  
  	if (expand_stack(vma, address))
  		goto bad_area;
  
  /*
   * Ok, we have a good vm_area for this memory access, so
   * we can handle it..
   */
  good_area:
  	info.si_code = SEGV_ACCERR;
  	switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
  	default:	/* 3: write, present */
  	case MMUFCR_xFC_TYPE_WRITE:
  #ifdef TEST_VERIFY_AREA
  		if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
  			printk(KERN_DEBUG "WP fault at %08lx
  ", regs->pc);
  #endif
  		/* write to absent page */
  	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  		flags |= FAULT_FLAG_WRITE;
  		break;
  
  		/* read from protected page */
  	case MMUFCR_xFC_TYPE_READ:
  		goto bad_area;
  
  		/* read from absent page present */
  	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_READ:
  		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
  			goto bad_area;
  		break;
  	}
  
  	/*
  	 * If for any reason at all we couldn't handle the fault,
  	 * make sure we exit gracefully rather than endlessly redo
  	 * the fault.
  	 */
  	fault = handle_mm_fault(mm, vma, address, flags);
  
  	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
  		return;
  
  	if (unlikely(fault & VM_FAULT_ERROR)) {
  		if (fault & VM_FAULT_OOM)
  			goto out_of_memory;
  		else if (fault & VM_FAULT_SIGBUS)
  			goto do_sigbus;
  		BUG();
  	}
  	if (flags & FAULT_FLAG_ALLOW_RETRY) {
  		if (fault & VM_FAULT_MAJOR)
  			current->maj_flt++;
  		else
  			current->min_flt++;
  		if (fault & VM_FAULT_RETRY) {
  			flags &= ~FAULT_FLAG_ALLOW_RETRY;
  
  			 /* No need to up_read(&mm->mmap_sem) as we would
  			 * have already released it in __lock_page_or_retry
  			 * in mm/filemap.c.
  			 */
  
  			goto retry;
  		}
  	}
  
  	up_read(&mm->mmap_sem);
  	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:
  	up_read(&mm->mmap_sem);
  
  	/* User mode accesses just cause a SIGSEGV */
  	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
  		info.si_signo = SIGSEGV;
  		info.si_errno = 0;
  		/* info.si_code has been set above */
  		info.si_addr = (void *)address;
  		force_sig_info(SIGSEGV, &info, tsk);
  		return;
  	}
  
  no_context:
  	/* Are we prepared to handle this kernel fault?  */
  	if (fixup_exception(regs))
  		return;
  
  /*
   * Oops. The kernel tried to access some bad page. We'll have to
   * terminate things with extreme prejudice.
   */
  
  	bust_spinlocks(1);
  
  	if (address < PAGE_SIZE)
  		printk(KERN_ALERT
  		       "Unable to handle kernel NULL pointer dereference");
  	else
  		printk(KERN_ALERT
  		       "Unable to handle kernel paging request");
  	printk(" at virtual address %08lx
  ", address);
  	printk(" printing pc:
  ");
  	printk(KERN_ALERT "%08lx
  ", regs->pc);
  
  	debugger_intercept(fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR,
  			   SIGSEGV, SEGV_ACCERR, regs);
  
  	page = PTBR;
  	page = ((unsigned long *) __va(page))[address >> 22];
  	printk(KERN_ALERT "*pde = %08lx
  ", page);
  	if (page & 1) {
  		page &= PAGE_MASK;
  		address &= 0x003ff000;
  		page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
  		printk(KERN_ALERT "*pte = %08lx
  ", page);
  	}
  
  	die("Oops", regs, fault_code);
  	do_exit(SIGKILL);
  
  /*
   * We ran out of memory, or some other thing happened to us that made
   * us unable to handle the page fault gracefully.
   */
  out_of_memory:
  	up_read(&mm->mmap_sem);
  	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
  		pagefault_out_of_memory();
  		return;
  	}
  	goto no_context;
  
  do_sigbus:
  	up_read(&mm->mmap_sem);
  
  	/*
  	 * Send a sigbus, regardless of whether we were in kernel
  	 * or user mode.
  	 */
  	info.si_signo = SIGBUS;
  	info.si_errno = 0;
  	info.si_code = BUS_ADRERR;
  	info.si_addr = (void *)address;
  	force_sig_info(SIGBUS, &info, tsk);
  
  	/* Kernel mode? Handle exceptions or die */
  	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
  		goto no_context;
  	return;
  
  vmalloc_fault:
  	{
  		/*
  		 * Synchronize this task's top level page-table
  		 * with the 'reference' page table.
  		 *
  		 * Do _not_ use "tsk" here. We might be inside
  		 * an interrupt in the middle of a task switch..
  		 */
  		int index = pgd_index(address);
  		pgd_t *pgd, *pgd_k;
  		pud_t *pud, *pud_k;
  		pmd_t *pmd, *pmd_k;
  		pte_t *pte_k;
  
  		pgd_k = init_mm.pgd + index;
  
  		if (!pgd_present(*pgd_k))
  			goto no_context;
  
  		pud_k = pud_offset(pgd_k, address);
  		if (!pud_present(*pud_k))
  			goto no_context;
  
  		pmd_k = pmd_offset(pud_k, address);
  		if (!pmd_present(*pmd_k))
  			goto no_context;
  
  		pgd = (pgd_t *) PTBR + index;
  		pud = pud_offset(pgd, address);
  		pmd = pmd_offset(pud, address);
  		set_pmd(pmd, *pmd_k);
  
  		pte_k = pte_offset_kernel(pmd_k, address);
  		if (!pte_present(*pte_k))
  			goto no_context;
  		return;
  	}
  }