text: // SPDX-License-Identifier: GPL-2.0
  /*
   * MMU fault handling support.
   *
   * Copyright (C) 1998-2002 Hewlett-Packard Co
   *	David Mosberger-Tang <davidm@hpl.hp.com>
   */
  #include <linux/sched/signal.h>
  #include <linux/kernel.h>
  #include <linux/mm.h>
  #include <linux/extable.h>
  #include <linux/interrupt.h>
  #include <linux/kprobes.h>
  #include <linux/kdebug.h>
  #include <linux/prefetch.h>
  #include <linux/uaccess.h>
  #include <linux/perf_event.h>
  
  #include <asm/processor.h>
  #include <asm/exception.h>
  
  extern int die(char *, struct pt_regs *, long);
  
  /*
   * 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;
  	p4d_t *p4d;
  	pud_t *pud;
  	pmd_t *pmd;
  	pte_t *ptep, pte;
  
  	pgd = pgd_offset_k(address);
  	if (pgd_none(*pgd) || pgd_bad(*pgd))
  		return 0;
  
  	p4d = p4d_offset(pgd, address);
  	if (p4d_none(*p4d) || p4d_bad(*p4d))
  		return 0;
  
  	pud = pud_offset(p4d, address);
  	if (pud_none(*pud) || pud_bad(*pud))
  		return 0;
  
  	pmd = pmd_offset(pud, address);
  	if (pmd_none(*pmd) || pmd_bad(*pmd))
  		return 0;
  
  	ptep = pte_offset_kernel(pmd, address);
  	if (!ptep)
  		return 0;
  
  	pte = *ptep;
  	return pte_present(pte);
  }
  
  #	define VM_READ_BIT	0
  #	define VM_WRITE_BIT	1
  #	define VM_EXEC_BIT	2
  
  void __kprobes
  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;
  	unsigned long mask;
  	vm_fault_t fault;
  	unsigned int flags = FAULT_FLAG_DEFAULT;
  
  	mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT)
  		| (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT));
  
  	/* mmap_lock is performance critical.... */
  	prefetchw(&mm->mmap_lock);
  
  	/*
  	 * If we're in an interrupt or have no user context, we must not take the fault..
  	 */
  	if (faulthandler_disabled() || !mm)
  		goto no_context;
  
  #ifdef CONFIG_VIRTUAL_MEM_MAP
  	/*
  	 * If fault is in region 5 and we are in the kernel, we may already
  	 * have the mmap_lock (pfn_valid macro is called during mmap). There
  	 * is no vma for region 5 addr's anyway, so skip getting the semaphore
  	 * and go directly to the exception handling code.
  	 */
  
  	if ((REGION_NUMBER(address) == 5) && !user_mode(regs))
  		goto bad_area_no_up;
  #endif
  
  	/*
  	 * This is to handle the kprobes on user space access instructions
  	 */
  	if (kprobe_page_fault(regs, TRAP_BRKPT))
  		return;
  
  	if (user_mode(regs))
  		flags |= FAULT_FLAG_USER;
  	if (mask & VM_WRITE)
  		flags |= FAULT_FLAG_WRITE;
  
  	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
  retry:
  	mmap_read_lock(mm);
  
  	vma = find_vma_prev(mm, address, &prev_vma);
  	if (!vma && !prev_vma )
  		goto bad_area;
  
          /*
           * find_vma_prev() returns vma such that address < vma->vm_end or NULL
           *
           * May find no vma, but could be that the last vm area is the
           * register backing store that needs to expand upwards, in
           * this case vma will be null, but prev_vma will ne non-null
           */
          if (( !vma && prev_vma ) || (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: */
  
  #	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>.  Please update.
  #	endif
  
  	if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE))))
  		goto bad_area;
  
  	if ((vma->vm_flags & mask) != mask)
  		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(vma, address, flags, regs);
  
  	if (fault_signal_pending(fault, regs))
  		return;
  
  	if (unlikely(fault & VM_FAULT_ERROR)) {
  		/*
  		 * We ran out of memory, or some other thing happened
  		 * to us that made us unable to handle the page fault
  		 * gracefully.
  		 */
  		if (fault & VM_FAULT_OOM) {
  			goto out_of_memory;
  		} else if (fault & VM_FAULT_SIGSEGV) {
  			goto bad_area;
  		} else if (fault & VM_FAULT_SIGBUS) {
  			signal = SIGBUS;
  			goto bad_area;
  		}
  		BUG();
  	}
  
  	if (flags & FAULT_FLAG_ALLOW_RETRY) {
  		if (fault & VM_FAULT_RETRY) {
  			flags |= FAULT_FLAG_TRIED;
  
  			 /* No need to mmap_read_unlock(mm) as we would
  			 * have already released it in __lock_page_or_retry
  			 * in mm/filemap.c.
  			 */
  
  			goto retry;
  		}
  	}
  
  	mmap_read_unlock(mm);
  	return;
  
    check_expansion:
  	if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) {
  		if (!vma)
  			goto bad_area;
  		if (!(vma->vm_flags & VM_GROWSDOWN))
  			goto bad_area;
  		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
  		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
  			goto bad_area;
  		if (expand_stack(vma, address))
  			goto bad_area;
  	} else {
  		vma = prev_vma;
  		if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start)
  		    || REGION_OFFSET(address) >= RGN_MAP_LIMIT)
  			goto bad_area;
  		/*
  		 * Since the register backing store is accessed sequentially,
  		 * we disallow growing it by more than a page at a time.
  		 */
  		if (address > vma->vm_end + PAGE_SIZE - sizeof(long))
  			goto bad_area;
  		if (expand_upwards(vma, address))
  			goto bad_area;
  	}
  	goto good_area;
  
    bad_area:
  	mmap_read_unlock(mm);
  #ifdef CONFIG_VIRTUAL_MEM_MAP
    bad_area_no_up:
  #endif
  	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)) {
  		force_sig_fault(signal, code, (void __user *) address,
  				0, __ISR_VALID, isr);
  		return;
  	}
  
    no_context:
  	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;
  	}
  
  	/*
  	 * 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;
  
  	if (ia64_done_with_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 (address %016lx)\n", address);
  	else
  		printk(KERN_ALERT "Unable to handle kernel paging request at "
  		       "virtual address %016lx\n", address);
  	if (die("Oops", regs, isr))
  		regs = NULL;
  	bust_spinlocks(0);
  	if (regs)
  		do_exit(SIGKILL);
  	return;
  
    out_of_memory:
  	mmap_read_unlock(mm);
  	if (!user_mode(regs))
  		goto no_context;
  	pagefault_out_of_memory();
  }
  