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fault.c

/*
 *  linux/arch/m32r/mm/fault.c
 *
 *  Copyright (c) 2001, 2002  Hitoshi Yamamoto, and H. Kondo
 *  Copyright (c) 2004  Naoto Sugai, NIIBE Yutaka
 *
 *  Some code taken from i386 version.
 *    Copyright (C) 1995  Linus Torvalds
 */

#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/tty.h>
#include <linux/vt_kern.h>          /* For unblank_screen() */
#include <linux/highmem.h>
#include <linux/module.h>

#include <asm/m32r.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/hardirq.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>

extern void die(const char *, struct pt_regs *, long);

#ifndef CONFIG_SMP
asmlinkage unsigned int tlb_entry_i_dat;
asmlinkage unsigned int tlb_entry_d_dat;
#define tlb_entry_i tlb_entry_i_dat
#define tlb_entry_d tlb_entry_d_dat
#else
unsigned int tlb_entry_i_dat[NR_CPUS];
unsigned int tlb_entry_d_dat[NR_CPUS];
#define tlb_entry_i tlb_entry_i_dat[smp_processor_id()]
#define tlb_entry_d tlb_entry_d_dat[smp_processor_id()]
#endif

extern void init_tlb(void);

/*======================================================================*
 * do_page_fault()
 *======================================================================*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 *
 * ARGUMENT:
 *  regs       : M32R SP reg.
 *  error_code : See below
 *  address    : M32R MMU MDEVA reg. (Operand ACE)
 *             : M32R BPC reg. (Instruction ACE)
 *
 * error_code :
 *  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
 *  bit 3 == 0 means data, 1 means instruction
 *======================================================================*/
#define ACE_PROTECTION        1
#define ACE_WRITE       2
#define ACE_USERMODE          4
#define ACE_INSTRUCTION       8

asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code,
  unsigned long address)
{
      struct task_struct *tsk;
      struct mm_struct *mm;
      struct vm_area_struct * vma;
      unsigned long page, addr;
      int write;
      int fault;
      siginfo_t info;

      /*
       * If BPSW IE bit enable --> set PSW IE bit
       */
      if (regs->psw & M32R_PSW_BIE)
            local_irq_enable();

      tsk = current;

      info.si_code = SEGV_MAPERR;

      /*
       * 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
       * (error_code & ACE_USERMODE) == 0, and that the fault was not a
       * protection error (error_code & ACE_PROTECTION) == 0.
       */
      if (address >= TASK_SIZE && !(error_code & ACE_USERMODE))
            goto vmalloc_fault;

      mm = tsk->mm;

      /*
       * If we're in an interrupt or have no user context or are running in an
       * atomic region then we must not take the fault..
       */
      if (in_atomic() || !mm)
            goto bad_area_nosemaphore;

      /* When running in the kernel we expect faults to occur only to
       * addresses in user space.  All other faults represent errors in the
       * kernel and should generate an OOPS.  Unfortunatly, in the case of an
       * erroneous fault occurring in a code path which already holds mmap_sem
       * we will deadlock attempting to validate the fault against the
       * address space.  Luckily the kernel only validly references user
       * space from well defined areas of code, which are listed in the
       * exceptions table.
       *
       * As the vast majority of faults will be valid we will only perform
       * the source reference check when there is a possibilty of a deadlock.
       * Attempt to lock the address space, if we cannot we then validate the
       * source.  If this is invalid we can skip the address space check,
       * thus avoiding the deadlock.
       */
      if (!down_read_trylock(&mm->mmap_sem)) {
            if ((error_code & ACE_USERMODE) == 0 &&
                !search_exception_tables(regs->psw))
                  goto bad_area_nosemaphore;
            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 (error_code & ACE_USERMODE) {
            /*
             * accessing the stack below "spu" is always a bug.
             * The "+ 4" is there due to the push instruction
             * doing pre-decrement on the stack and that
             * doesn't show up until later..
             */
            if (address + 4 < regs->spu)
                  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 (error_code & (ACE_WRITE|ACE_PROTECTION)) {
            default:    /* 3: write, present */
                  /* fall through */
            case ACE_WRITE:   /* write, not present */
                  if (!(vma->vm_flags & VM_WRITE))
                        goto bad_area;
                  write++;
                  break;
            case ACE_PROTECTION:    /* read, present */
            case 0:           /* read, not present */
                  if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
                        goto bad_area;
      }

      /*
       * For instruction access exception, check if the area is executable
       */
      if ((error_code & ACE_INSTRUCTION) && !(vma->vm_flags & VM_EXEC))
        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.
       */
      addr = (address & PAGE_MASK);
      set_thread_fault_code(error_code);
      fault = handle_mm_fault(mm, vma, addr, write ? FAULT_FLAG_WRITE : 0);
      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)
            tsk->maj_flt++;
      else
            tsk->min_flt++;
      set_thread_fault_code(0);
      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);

bad_area_nosemaphore:
      /* User mode accesses just cause a SIGSEGV */
      if (error_code & ACE_USERMODE) {
            tsk->thread.address = address;
            tsk->thread.error_code = error_code | (address >= TASK_SIZE);
            tsk->thread.trap_no = 14;
            info.si_signo = SIGSEGV;
            info.si_errno = 0;
            /* info.si_code has been set above */
            info.si_addr = (void __user *)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\n",address);
      printk(KERN_ALERT " printing bpc:\n");
      printk("%08lx\n", regs->bpc);
      page = *(unsigned long *)MPTB;
      page = ((unsigned long *) page)[address >> PGDIR_SHIFT];
      printk(KERN_ALERT "*pde = %08lx\n", page);
      if (page & _PAGE_PRESENT) {
            page &= PAGE_MASK;
            address &= 0x003ff000;
            page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
            printk(KERN_ALERT "*pte = %08lx\n", page);
      }
      die("Oops", regs, error_code);
      bust_spinlocks(0);
      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 (is_global_init(tsk)) {
            yield();
            down_read(&mm->mmap_sem);
            goto survive;
      }
      printk("VM: killing process %s\n", tsk->comm);
      if (error_code & ACE_USERMODE)
            do_group_exit(SIGKILL);
      goto no_context;

do_sigbus:
      up_read(&mm->mmap_sem);

      /* Kernel mode? Handle exception or die */
      if (!(error_code & ACE_USERMODE))
            goto no_context;

      tsk->thread.address = address;
      tsk->thread.error_code = error_code;
      tsk->thread.trap_no = 14;
      info.si_signo = SIGBUS;
      info.si_errno = 0;
      info.si_code = BUS_ADRERR;
      info.si_addr = (void __user *)address;
      force_sig_info(SIGBUS, &info, tsk);
      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 offset = pgd_index(address);
            pgd_t *pgd, *pgd_k;
            pmd_t *pmd, *pmd_k;
            pte_t *pte_k;

            pgd = (pgd_t *)*(unsigned long *)MPTB;
            pgd = offset + (pgd_t *)pgd;
            pgd_k = init_mm.pgd + offset;

            if (!pgd_present(*pgd_k))
                  goto no_context;

            /*
             * set_pgd(pgd, *pgd_k); here would be useless on PAE
             * and redundant with the set_pmd() on non-PAE.
             */

            pmd = pmd_offset(pgd, address);
            pmd_k = pmd_offset(pgd_k, address);
            if (!pmd_present(*pmd_k))
                  goto no_context;
            set_pmd(pmd, *pmd_k);

            pte_k = pte_offset_kernel(pmd_k, address);
            if (!pte_present(*pte_k))
                  goto no_context;

            addr = (address & PAGE_MASK);
            set_thread_fault_code(error_code);
            update_mmu_cache(NULL, addr, *pte_k);
            set_thread_fault_code(0);
            return;
      }
}

/*======================================================================*
 * update_mmu_cache()
 *======================================================================*/
#define TLB_MASK  (NR_TLB_ENTRIES - 1)
#define ITLB_END  (unsigned long *)(ITLB_BASE + (NR_TLB_ENTRIES * 8))
#define DTLB_END  (unsigned long *)(DTLB_BASE + (NR_TLB_ENTRIES * 8))
void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr,
      pte_t pte)
{
      volatile unsigned long *entry1, *entry2;
      unsigned long pte_data, flags;
      unsigned int *entry_dat;
      int inst = get_thread_fault_code() & ACE_INSTRUCTION;
      int i;

      /* Ptrace may call this routine. */
      if (vma && current->active_mm != vma->vm_mm)
            return;

      local_irq_save(flags);

      vaddr = (vaddr & PAGE_MASK) | get_asid();

      pte_data = pte_val(pte);

#ifdef CONFIG_CHIP_OPSP
      entry1 = (unsigned long *)ITLB_BASE;
      for (i = 0; i < NR_TLB_ENTRIES; i++) {
            if (*entry1++ == vaddr) {
                  set_tlb_data(entry1, pte_data);
                  break;
            }
            entry1++;
      }
      entry2 = (unsigned long *)DTLB_BASE;
      for (i = 0; i < NR_TLB_ENTRIES; i++) {
            if (*entry2++ == vaddr) {
                  set_tlb_data(entry2, pte_data);
                  break;
            }
            entry2++;
      }
#else
      /*
       * Update TLB entries
       *  entry1: ITLB entry address
       *  entry2: DTLB entry address
       */
      __asm__ __volatile__ (
            "seth %0, #high(%4)     \n\t"
            "st   %2, @(%5, %0)     \n\t"
            "ldi  %1, #1            \n\t"
            "st   %1, @(%6, %0)     \n\t"
            "add3 r4, %0, %7  \n\t"
            ".fillinsn        \n"
            "1:               \n\t"
            "ld   %1, @(%6, %0)     \n\t"
            "bnez %1, 1b            \n\t"
            "ld   %0, @r4+    \n\t"
            "ld   %1, @r4           \n\t"
            "st   %3, @+%0    \n\t"
            "st   %3, @+%1    \n\t"
            : "=&r" (entry1), "=&r" (entry2)
            : "r" (vaddr), "r" (pte_data), "i" (MMU_REG_BASE),
            "i" (MSVA_offset), "i" (MTOP_offset), "i" (MIDXI_offset)
            : "r4", "memory"
      );
#endif

      if ((!inst && entry2 >= DTLB_END) || (inst && entry1 >= ITLB_END))
            goto notfound;

found:
      local_irq_restore(flags);

      return;

      /* Valid entry not found */
notfound:
      /*
       * Update ITLB or DTLB entry
       *  entry1: TLB entry address
       *  entry2: TLB base address
       */
      if (!inst) {
            entry2 = (unsigned long *)DTLB_BASE;
            entry_dat = &tlb_entry_d;
      } else {
            entry2 = (unsigned long *)ITLB_BASE;
            entry_dat = &tlb_entry_i;
      }
      entry1 = entry2 + (((*entry_dat - 1) & TLB_MASK) << 1);

      for (i = 0 ; i < NR_TLB_ENTRIES ; i++) {
            if (!(entry1[1] & 2))   /* Valid bit check */
                  break;

            if (entry1 != entry2)
                  entry1 -= 2;
            else
                  entry1 += TLB_MASK << 1;
      }

      if (i >= NR_TLB_ENTRIES) {    /* Empty entry not found */
            entry1 = entry2 + (*entry_dat << 1);
            *entry_dat = (*entry_dat + 1) & TLB_MASK;
      }
      *entry1++ = vaddr;      /* Set TLB tag */
      set_tlb_data(entry1, pte_data);

      goto found;
}

/*======================================================================*
 * flush_tlb_page() : flushes one page
 *======================================================================*/
void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
{
      if (vma->vm_mm && mm_context(vma->vm_mm) != NO_CONTEXT) {
            unsigned long flags;

            local_irq_save(flags);
            page &= PAGE_MASK;
            page |= (mm_context(vma->vm_mm) & MMU_CONTEXT_ASID_MASK);
            __flush_tlb_page(page);
            local_irq_restore(flags);
      }
}

/*======================================================================*
 * flush_tlb_range() : flushes a range of pages
 *======================================================================*/
void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
      unsigned long end)
{
      struct mm_struct *mm;

      mm = vma->vm_mm;
      if (mm_context(mm) != NO_CONTEXT) {
            unsigned long flags;
            int size;

            local_irq_save(flags);
            size = (end - start + (PAGE_SIZE - 1)) >> PAGE_SHIFT;
            if (size > (NR_TLB_ENTRIES / 4)) { /* Too many TLB to flush */
                  mm_context(mm) = NO_CONTEXT;
                  if (mm == current->mm)
                        activate_context(mm);
            } else {
                  unsigned long asid;

                  asid = mm_context(mm) & MMU_CONTEXT_ASID_MASK;
                  start &= PAGE_MASK;
                  end += (PAGE_SIZE - 1);
                  end &= PAGE_MASK;

                  start |= asid;
                  end   |= asid;
                  while (start < end) {
                        __flush_tlb_page(start);
                        start += PAGE_SIZE;
                  }
            }
            local_irq_restore(flags);
      }
}

/*======================================================================*
 * flush_tlb_mm() : flushes the specified mm context TLB's
 *======================================================================*/
void local_flush_tlb_mm(struct mm_struct *mm)
{
      /* Invalidate all TLB of this process. */
      /* Instead of invalidating each TLB, we get new MMU context. */
      if (mm_context(mm) != NO_CONTEXT) {
            unsigned long flags;

            local_irq_save(flags);
            mm_context(mm) = NO_CONTEXT;
            if (mm == current->mm)
                  activate_context(mm);
            local_irq_restore(flags);
      }
}

/*======================================================================*
 * flush_tlb_all() : flushes all processes TLBs
 *======================================================================*/
void local_flush_tlb_all(void)
{
      unsigned long flags;

      local_irq_save(flags);
      __flush_tlb_all();
      local_irq_restore(flags);
}

/*======================================================================*
 * init_mmu()
 *======================================================================*/
void __init init_mmu(void)
{
      tlb_entry_i = 0;
      tlb_entry_d = 0;
      mmu_context_cache = MMU_CONTEXT_FIRST_VERSION;
      set_asid(mmu_context_cache & MMU_CONTEXT_ASID_MASK);
      *(volatile unsigned long *)MPTB = (unsigned long)swapper_pg_dir;
}

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