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fault.c

/* 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/smp_lock.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <linux/vt_kern.h>          /* For unblank_screen() */

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/hardirq.h>
#include <asm/gdb-stub.h>
#include <asm/cpu-regs.h>

/*
 * Unlock any spinlocks which will prevent us from getting the
 * message out
 */
void bust_spinlocks(int yes)
{
      if (yes) {
            oops_in_progress = 1;
#ifdef CONFIG_SMP
            /* Many serial drivers do __global_cli() */
            global_irq_lock = 0;
#endif
      } 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 ]------------\n");
      printk(KERN_EMERG "kernel BUG at %s:%d!\n", 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\n",
             pgd, (long long) pgd_val(*pgd));

      if (!pgd_present(*pgd)) {
            printk(KERN_DEBUG "... pgd not present!\n");
            return;
      }
      pmd = pmd_offset(pgd, address);
      printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
             pmd, (long long)pmd_val(*pmd));

      if (!pmd_present(*pmd)) {
            printk(KERN_DEBUG "... pmd not present!\n");
            return;
      }
      pte = pte_offset(pmd, address);
      printk(KERN_DEBUG "pte entry %p: %016Lx\n",
             pte, (long long) pte_val(*pte));

      if (!pte_present(*pte))
            printk(KERN_DEBUG "... pte not present!\n");
}
#endif

asmlinkage void monitor_signal(struct pt_regs *);

/*
 * 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 write, fault;

#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)\n",
             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_interrupt() || !mm)
            goto no_context;

      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)\n",
                         current->pid, address, regs->sp);
                  printk(KERN_WARNING
                         "vma [%08x - %08x]\n",
                         vma->vm_start, vma->vm_end);
                  show_registers(regs);
                  printk(KERN_WARNING
                         "[%d] ### Code: [%08lx]"
                         " %02x %02x %02x %02x %02x %02x %02x %02x\n",
                         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;
      write = 0;
      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\n", regs->pc);
#endif
            /* write to absent page */
      case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
            if (!(vma->vm_flags & VM_WRITE))
                  goto bad_area;
            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, 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);
      monitor_signal(regs);

      /* 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:
      monitor_signal(regs);
      /* 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\n", address);
      printk(" printing pc:\n");
      printk(KERN_ALERT "%08lx\n", regs->pc);

#ifdef CONFIG_GDBSTUB
      gdbstub_intercept(
            regs, fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR);
#endif

      page = PTBR;
      page = ((unsigned long *) __va(page))[address >> 22];
      printk(KERN_ALERT "*pde = %08lx\n", page);
      if (page & 1) {
            page &= PAGE_MASK;
            address &= 0x003ff000;
            page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
            printk(KERN_ALERT "*pte = %08lx\n", 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);
      monitor_signal(regs);
      printk(KERN_ALERT "VM: killing process %s\n", tsk->comm);
      if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
            do_exit(SIGKILL);
      goto no_context;

do_sigbus:
      up_read(&mm->mmap_sem);
      monitor_signal(regs);

      /*
       * 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;
      }
}

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