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fault.c

/*
 *  linux/arch/frv/mm/fault.c
 *
 * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
 * - Written by David Howells (dhowells@redhat.com)
 * - Derived from arch/m68knommu/mm/fault.c
 *   - Copyright (C) 1998  D. Jeff Dionne <jeff@lineo.ca>,
 *   - Copyright (C) 2000  Lineo, Inc.  (www.lineo.com)
 *
 *  Based on:
 *
 *  linux/arch/m68k/mm/fault.c
 *
 *  Copyright (C) 1995  Hamish Macdonald
 */

#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/hardirq.h>

#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/gdb-stub.h>

/*****************************************************************************/
/*
 * This routine handles page faults.  It determines the problem, and
 * then passes it off to one of the appropriate routines.
 */
asmlinkage void do_page_fault(int datammu, unsigned long esr0, unsigned long ear0)
{
      struct vm_area_struct *vma;
      struct mm_struct *mm;
      unsigned long _pme, lrai, lrad, fixup;
      siginfo_t info;
      pgd_t *pge;
      pud_t *pue;
      pte_t *pte;
      int write;
      int fault;

#if 0
      const char *atxc[16] = {
            [0x0] = "mmu-miss", [0x8] = "multi-dat", [0x9] = "multi-sat",
            [0xa] = "tlb-miss", [0xc] = "privilege", [0xd] = "write-prot",
      };

      printk("do_page_fault(%d,%lx [%s],%lx)\n",
             datammu, esr0, atxc[esr0 >> 20 & 0xf], ear0);
#endif

      mm = current->mm;

      /*
       * 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 (!user_mode(__frame) && (esr0 & ESR0_ATXC) == ESR0_ATXC_AMRTLB_MISS) {
            if (ear0 >= VMALLOC_START && ear0 < VMALLOC_END)
                  goto kernel_pte_fault;
            if (ear0 >= PKMAP_BASE && ear0 < PKMAP_END)
                  goto kernel_pte_fault;
      }

      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;

      down_read(&mm->mmap_sem);

      vma = find_vma(mm, ear0);
      if (!vma)
            goto bad_area;
      if (vma->vm_start <= ear0)
            goto good_area;
      if (!(vma->vm_flags & VM_GROWSDOWN))
            goto bad_area;

      if (user_mode(__frame)) {
            /*
             * accessing the stack below %esp is always a bug.
             * The "+ 32" is there due to some instructions (like
             * pusha) doing post-decrement on the stack and that
             * doesn't show up until later..
             */
            if ((ear0 & PAGE_MASK) + 2 * PAGE_SIZE < __frame->sp) {
#if 0
                  printk("[%d] ### Access below stack @%lx (sp=%lx)\n",
                         current->pid, ear0, __frame->sp);
                  show_registers(__frame);
                  printk("[%d] ### Code: [%08lx] %02x %02x %02x %02x %02x %02x %02x %02x\n",
                         current->pid,
                         __frame->pc,
                         ((u8*)__frame->pc)[0],
                         ((u8*)__frame->pc)[1],
                         ((u8*)__frame->pc)[2],
                         ((u8*)__frame->pc)[3],
                         ((u8*)__frame->pc)[4],
                         ((u8*)__frame->pc)[5],
                         ((u8*)__frame->pc)[6],
                         ((u8*)__frame->pc)[7]
                         );
#endif
                  goto bad_area;
            }
      }

      if (expand_stack(vma, ear0))
            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;
      write = 0;
      switch (esr0 & ESR0_ATXC) {
      default:
            /* handle write to write protected page */
      case ESR0_ATXC_WP_EXCEP:
#ifdef TEST_VERIFY_AREA
            if (!(user_mode(__frame)))
                  printk("WP fault at %08lx\n", __frame->pc);
#endif
            if (!(vma->vm_flags & VM_WRITE))
                  goto bad_area;
            write = 1;
            break;

             /* handle read from protected page */
      case ESR0_ATXC_PRIV_EXCEP:
            goto bad_area;

             /* handle read, write or exec on absent page
              * - can't support write without permitting read
              * - don't support execute without permitting read and vice-versa
              */
      case ESR0_ATXC_AMRTLB_MISS:
            if (!(vma->vm_flags & (VM_READ | VM_WRITE | 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, ear0, write);
      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 (fault & VM_FAULT_MAJOR)
            current->maj_flt++;
      else
            current->min_flt++;

      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 (user_mode(__frame)) {
            info.si_signo = SIGSEGV;
            info.si_errno = 0;
            /* info.si_code has been set above */
            info.si_addr = (void *) ear0;
            force_sig_info(SIGSEGV, &info, current);
            return;
      }

 no_context:
      /* are we prepared to handle this kernel fault? */
      if ((fixup = search_exception_table(__frame->pc)) != 0) {
            __frame->pc = fixup;
            return;
      }

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */

      bust_spinlocks(1);

      if (ear0 < 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 addr %08lx\n", ear0);
      printk("  PC  : %08lx\n", __frame->pc);
      printk("  EXC : esr0=%08lx ear0=%08lx\n", esr0, ear0);

      asm("lrai %1,%0,#1,#0,#0" : "=&r"(lrai) : "r"(ear0));
      asm("lrad %1,%0,#1,#0,#0" : "=&r"(lrad) : "r"(ear0));

      printk(KERN_ALERT "  LRAI: %08lx\n", lrai);
      printk(KERN_ALERT "  LRAD: %08lx\n", lrad);

      __break_hijack_kernel_event();

      pge = pgd_offset(current->mm, ear0);
      pue = pud_offset(pge, ear0);
      _pme = pue->pue[0].ste[0];

      printk(KERN_ALERT "  PGE : %8p { PME %08lx }\n", pge, _pme);

      if (_pme & xAMPRx_V) {
            unsigned long dampr, damlr, val;

            asm volatile("movsg dampr2,%0 ! movgs %2,dampr2 ! movsg damlr2,%1"
                       : "=&r"(dampr), "=r"(damlr)
                       : "r" (_pme | xAMPRx_L|xAMPRx_SS_16Kb|xAMPRx_S|xAMPRx_C|xAMPRx_V)
                       );

            pte = (pte_t *) damlr + __pte_index(ear0);
            val = pte_val(*pte);

            asm volatile("movgs %0,dampr2" :: "r" (dampr));

            printk(KERN_ALERT "  PTE : %8p { %08lx }\n", pte, val);
      }

      die_if_kernel("Oops\n");
      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);
      printk("VM: killing process %s\n", current->comm);
      if (user_mode(__frame))
            do_group_exit(SIGKILL);
      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 *) ear0;
      force_sig_info(SIGBUS, &info, current);

      /* Kernel mode? Handle exceptions or die */
      if (!user_mode(__frame))
            goto no_context;
      return;

/*
 * The fault was caused by a kernel PTE (such as installed by vmalloc or kmap)
 */
 kernel_pte_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(ear0);
            pgd_t *pgd, *pgd_k;
            pud_t *pud, *pud_k;
            pmd_t *pmd, *pmd_k;
            pte_t *pte_k;

            pgd = (pgd_t *) __get_TTBR();
            pgd = (pgd_t *)__va(pgd) + index;
            pgd_k = ((pgd_t *)(init_mm.pgd)) + index;

            if (!pgd_present(*pgd_k))
                  goto no_context;
            //set_pgd(pgd, *pgd_k); /////// gcc ICE's on this line

            pud_k = pud_offset(pgd_k, ear0);
            if (!pud_present(*pud_k))
                  goto no_context;

            pmd_k = pmd_offset(pud_k, ear0);
            if (!pmd_present(*pmd_k))
                  goto no_context;

            pud = pud_offset(pgd, ear0);
            pmd = pmd_offset(pud, ear0);
            set_pmd(pmd, *pmd_k);

            pte_k = pte_offset_kernel(pmd_k, ear0);
            if (!pte_present(*pte_k))
                  goto no_context;
            return;
      }
} /* end do_page_fault() */

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