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/*
 * MMU fault handling support.
 *
 * Copyright (C) 1998-2002 Hewlett-Packard Co
 *	David Mosberger-Tang <davidm@hpl.hp.com>
 */
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>
 
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/hardirq.h>
 
extern void die (char *, struct pt_regs *, long);
 
/*
 * This routine is analogous to expand_stack() but instead grows the
 * register backing store (which grows towards higher addresses).
 * Since the register backing store is access sequentially, we
 * disallow growing the RBS by more than a page at a time.  Note that
 * the VM_GROWSUP flag can be set on any VM area but that's fine
 * because the total process size is still limited by RLIMIT_STACK and
 * RLIMIT_AS.
 */
static inline long
expand_backing_store (struct vm_area_struct *vma, unsigned long address)
{
	unsigned long grow;
 
	grow = PAGE_SIZE >> PAGE_SHIFT;
	if (address - vma->vm_start > current->rlim[RLIMIT_STACK].rlim_cur
	    || (((vma->vm_mm->total_vm + grow) << PAGE_SHIFT) > current->rlim[RLIMIT_AS].rlim_cur))
		return -ENOMEM;
	vma->vm_end += PAGE_SIZE;
	vma->vm_mm->total_vm += grow;
	if (vma->vm_flags & VM_LOCKED)
		vma->vm_mm->locked_vm += grow;
	return 0;
}
 
/*
 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment
 * (inside region 5, on ia64) and that page is present.
 */
static int
mapped_kernel_page_is_present (unsigned long address)
{
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t *ptep, pte;
 
	pgd = pgd_offset_k(address);
	if (pgd_none(*pgd) || pgd_bad(*pgd))
		return 0;
 
	pmd = pmd_offset(pgd,address);
	if (pmd_none(*pmd) || pmd_bad(*pmd))
		return 0;
 
	ptep = pte_offset(pmd, address);
	if (!ptep)
		return 0;
 
	pte = *ptep;
	return pte_present(pte);
}
 
void
ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs)
{
	int signal = SIGSEGV, code = SEGV_MAPERR;
	struct vm_area_struct *vma, *prev_vma;
	struct mm_struct *mm = current->mm;
	struct siginfo si;
	unsigned long mask;
 
	/*
	 * If we're in an interrupt or have no user context, we must not take the fault..
	 */
	if (in_interrupt() || !mm)
		goto no_context;
 
	/*
	 * If fault is in region 5 and we are in the kernel, we may already
         * have the mmap_sem (VALID_PAGE macro is called during mmap). There
	 * should be no vma for region 5 addr's anyway, so skip getting the
	 * semaphore and go directly to the code that handles a bad area.
  	 */
	if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
		goto bad_area_no_up;
 
	down_read(&mm->mmap_sem);
 
	vma = find_vma_prev(mm, address, &prev_vma);
	if (!vma)
		goto bad_area;
 
	/* find_vma_prev() returns vma such that address < vma->vm_end or NULL */
	if (address < vma->vm_start)
		goto check_expansion;
 
  good_area:
	code = SEGV_ACCERR;
 
	/* OK, we've got a good vm_area for this memory area.  Check the access permissions: */
 
#	define VM_READ_BIT	0
#	define VM_WRITE_BIT	1
#	define VM_EXEC_BIT	2
 
#	if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \
	    || (1 << VM_EXEC_BIT) != VM_EXEC)
#		error File is out of sync with <linux/mm.h>.  Pleaes update.
#	endif
 
	mask = (  (((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)
		| (((isr >> IA64_ISR_R_BIT) & 1UL) << VM_READ_BIT));
 
	if ((vma->vm_flags & mask) != mask)
		goto bad_area;
 
  survive:
	/*
	 * If for any reason at all we couldn't handle the fault, make
	 * sure we exit gracefully rather than endlessly redo the
	 * fault.
	 */
	switch (handle_mm_fault(mm, vma, address, (mask & VM_WRITE) != 0)) {
	      case 1:
		++current->min_flt;
		break;
	      case 2:
		++current->maj_flt;
		break;
	      case 0:
		/*
		 * We ran out of memory, or some other thing happened
		 * to us that made us unable to handle the page fault
		 * gracefully.
		 */
		signal = SIGBUS;
		goto bad_area;
	      default:
		goto out_of_memory;
	}
	up_read(&mm->mmap_sem);
	return;
 
  check_expansion:
	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
		if (!(vma->vm_flags & VM_GROWSDOWN))
			goto bad_area;
		if (rgn_index(address) != rgn_index(vma->vm_start)
		    || rgn_offset(address) >= RGN_MAP_LIMIT)
			goto bad_area;
		if (expand_stack(vma, address))
			goto bad_area;
	} else {
		vma = prev_vma;
		if (rgn_index(address) != rgn_index(vma->vm_start)
		    || rgn_offset(address) >= RGN_MAP_LIMIT)
			goto bad_area;
		if (expand_backing_store(vma, address))
			goto bad_area;
	}
	goto good_area;
 
  bad_area:
	up_read(&mm->mmap_sem);
  bad_area_no_up:
	if ((isr & IA64_ISR_SP)
	    || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH))
	{
		/*
		 * This fault was due to a speculative load or lfetch.fault, set the "ed"
		 * bit in the psr to ensure forward progress.  (Target register will get a
		 * NaT for ld.s, lfetch will be canceled.)
		 */
		ia64_psr(regs)->ed = 1;
		return;
	}
	if (user_mode(regs)) {
		si.si_signo = signal;
		si.si_errno = 0;
		si.si_code = code;
		si.si_addr = (void *) address;
		si.si_isr = isr;
		si.si_flags = __ISR_VALID;
		force_sig_info(signal, &si, current);
		return;
	}
 
  no_context:
	if (isr & IA64_ISR_SP) {
		/*
		 * This fault was due to a speculative load set the "ed" bit in the psr to
		 * ensure forward progress (target register will get a NaT).
		 */
		ia64_psr(regs)->ed = 1;
		return;
	}
 
	if (done_with_exception(regs))
		return;
 
	/*
	 * Since we have no vma's for region 5, we might get here even if the address is
	 * valid, due to the VHPT walker inserting a non present translation that becomes
	 * stale. If that happens, the non present fault handler already purged the stale
	 * translation, which fixed the problem. So, we check to see if the translation is
	 * valid, and return if it is.
	 */
	if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address))
		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 at "
		       "virtual address %016lx\n", address);
	die("Oops", regs, isr);
	bust_spinlocks(0);
	do_exit(SIGKILL);
	return;
 
  out_of_memory:
	if (current->pid == 1) {
		yield();
		goto survive;
	}
	up_read(&mm->mmap_sem);
	printk(KERN_CRIT "VM: killing process %s\n", current->comm);
	if (user_mode(regs))
		do_exit(SIGKILL);
	goto no_context;
}