/*
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file "COPYING" in the main directory of this archive
   * for more details.
   *
   * Copyright (C) 1995 - 2000 by Ralf Baechle
   */
  #include <linux/context_tracking.h>
  #include <linux/signal.h>
  #include <linux/sched.h>
  #include <linux/interrupt.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/module.h>
  #include <linux/kprobes.h>
  #include <linux/perf_event.h>
  
  #include <asm/branch.h>
  #include <asm/mmu_context.h>
  #include <asm/uaccess.h>
  #include <asm/ptrace.h>
  #include <asm/highmem.h>		/* For VMALLOC_END */
  #include <linux/kdebug.h>
  
  /*
   * This routine handles page faults.  It determines the address,
   * and the problem, and then passes it off to one of the appropriate
   * routines.
   */
  static void __kprobes __do_page_fault(struct pt_regs *regs, unsigned long write,
  	unsigned long address)
  {
  	struct vm_area_struct * vma = NULL;
  	struct task_struct *tsk = current;
  	struct mm_struct *mm = tsk->mm;
  	const int field = sizeof(unsigned long) * 2;
  	siginfo_t info;
  	int fault;
  	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  
  #if 0
  	printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]
  ", raw_smp_processor_id(),
  	       current->comm, current->pid, field, address, write,
  	       field, regs->cp0_epc);
  #endif
  
  #ifdef CONFIG_KPROBES
  	/*
  	 * This is to notify the fault handler of the kprobes.	The
  	 * exception code is redundant as it is also carried in REGS,
  	 * but we pass it anyhow.
  	 */
  	if (notify_die(DIE_PAGE_FAULT, "page fault", regs, -1,
  		       (regs->cp0_cause >> 2) & 0x1f, SIGSEGV) == NOTIFY_STOP)
  		return;
  #endif
  
  	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.
  	 */
  #ifdef CONFIG_64BIT
  # define VMALLOC_FAULT_TARGET no_context
  #else
  # define VMALLOC_FAULT_TARGET vmalloc_fault
  #endif
  
  	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
  		goto VMALLOC_FAULT_TARGET;
  #ifdef MODULE_START
  	if (unlikely(address >= MODULE_START && address < MODULE_END))
  		goto VMALLOC_FAULT_TARGET;
  #endif
  
  	/*
  	 * If we're in an interrupt or have no user
  	 * context, we must not take the fault..
  	 */
  	if (in_atomic() || !mm)
  		goto bad_area_nosemaphore;
  
  	if (user_mode(regs))
  		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 (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;
  
  	if (write) {
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  		flags |= FAULT_FLAG_WRITE;
  	} else {
  		if (cpu_has_rixi) {
  			if (address == regs->cp0_epc && !(vma->vm_flags & VM_EXEC)) {
  #if 0
  				pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] XI violation
  ",
  					  raw_smp_processor_id(),
  					  current->comm, current->pid,
  					  field, address, write,
  					  field, regs->cp0_epc);
  #endif
  				goto bad_area;
  			}
  			if (!(vma->vm_flags & VM_READ)) {
  #if 0
  				pr_notice("Cpu%d[%s:%d:%0*lx:%ld:%0*lx] RI violation
  ",
  					  raw_smp_processor_id(),
  					  current->comm, current->pid,
  					  field, address, write,
  					  field, regs->cp0_epc);
  #endif
  				goto bad_area;
  			}
  		} else {
  			if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
  				goto bad_area;
  		}
  	}
  
  	/*
  	 * 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;
  
  	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  	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) {
  			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
  						  regs, address);
  			tsk->maj_flt++;
  		} else {
  			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
  						  regs, address);
  			tsk->min_flt++;
  		}
  		if (fault & VM_FAULT_RETRY) {
  			flags &= ~FAULT_FLAG_ALLOW_RETRY;
  			flags |= FAULT_FLAG_TRIED;
  
  			/*
  			 * 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);
  
  bad_area_nosemaphore:
  	/* User mode accesses just cause a SIGSEGV */
  	if (user_mode(regs)) {
  		tsk->thread.cp0_badvaddr = address;
  		tsk->thread.error_code = write;
  #if 0
  		printk("do_page_fault() #2: sending SIGSEGV to %s for "
  		       "invalid %s
  %0*lx (epc == %0*lx, ra == %0*lx)
  ",
  		       tsk->comm,
  		       write ? "write access to" : "read access from",
  		       field, address,
  		       field, (unsigned long) regs->cp0_epc,
  		       field, (unsigned long) regs->regs[31]);
  #endif
  		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)) {
  		current->thread.cp0_baduaddr = address;
  		return;
  	}
  
  	/*
  	 * Oops. The kernel tried to access some bad page. We'll have to
  	 * terminate things with extreme prejudice.
  	 */
  	bust_spinlocks(1);
  
  	printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
  	       "virtual address %0*lx, epc == %0*lx, ra == %0*lx
  ",
  	       raw_smp_processor_id(), field, address, field, regs->cp0_epc,
  	       field,  regs->regs[31]);
  	die("Oops", regs);
  
  out_of_memory:
  	/*
  	 * We ran out of memory, call the OOM killer, and return the userspace
  	 * (which will retry the fault, or kill us if we got oom-killed).
  	 */
  	up_read(&mm->mmap_sem);
  	if (!user_mode(regs))
  		goto no_context;
  	pagefault_out_of_memory();
  	return;
  
  do_sigbus:
  	up_read(&mm->mmap_sem);
  
  	/* Kernel mode? Handle exceptions or die */
  	if (!user_mode(regs))
  		goto no_context;
  	else
  	/*
  	 * Send a sigbus, regardless of whether we were in kernel
  	 * or user mode.
  	 */
  #if 0
  		printk("do_page_fault() #3: sending SIGBUS to %s for "
  		       "invalid %s
  %0*lx (epc == %0*lx, ra == %0*lx)
  ",
  		       tsk->comm,
  		       write ? "write access to" : "read access from",
  		       field, address,
  		       field, (unsigned long) regs->cp0_epc,
  		       field, (unsigned long) regs->regs[31]);
  #endif
  	tsk->thread.cp0_badvaddr = address;
  	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;
  #ifndef CONFIG_64BIT
  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_offset(address);
  		pgd_t *pgd, *pgd_k;
  		pud_t *pud, *pud_k;
  		pmd_t *pmd, *pmd_k;
  		pte_t *pte_k;
  
  		pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
  		pgd_k = init_mm.pgd + offset;
  
  		if (!pgd_present(*pgd_k))
  			goto no_context;
  		set_pgd(pgd, *pgd_k);
  
  		pud = pud_offset(pgd, address);
  		pud_k = pud_offset(pgd_k, address);
  		if (!pud_present(*pud_k))
  			goto no_context;
  
  		pmd = pmd_offset(pud, address);
  		pmd_k = pmd_offset(pud_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;
  		return;
  	}
  #endif
  }
  
  asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
  	unsigned long write, unsigned long address)
  {
  	enum ctx_state prev_state;
  
  	prev_state = exception_enter();
  	__do_page_fault(regs, write, address);
  	exception_exit(prev_state);
  }