text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Memory fault handling for Hexagon
   *
   * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
   */
  
  /*
   * Page fault handling for the Hexagon Virtual Machine.
   * Can also be called by a native port emulating the HVM
   * execptions.
   */
  
  #include <asm/pgtable.h>
  #include <asm/traps.h>
  #include <linux/uaccess.h>
  #include <linux/mm.h>
  #include <linux/sched/signal.h>
  #include <linux/signal.h>
  #include <linux/extable.h>
  #include <linux/hardirq.h>
  
  /*
   * Decode of hardware exception sends us to one of several
   * entry points.  At each, we generate canonical arguments
   * for handling by the abstract memory management code.
   */
  #define FLT_IFETCH     -1
  #define FLT_LOAD        0
  #define FLT_STORE       1
  
  
  /*
   * Canonical page fault handler
   */
  void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
  {
  	struct vm_area_struct *vma;
  	struct mm_struct *mm = current->mm;
  	int si_signo;
  	int si_code = SEGV_MAPERR;
  	vm_fault_t fault;
  	const struct exception_table_entry *fixup;
  	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
  
  	/*
  	 * If we're in an interrupt or have no user context,
  	 * then must not take the fault.
  	 */
  	if (unlikely(in_interrupt() || !mm))
  		goto no_context;
  
  	local_irq_enable();
  
  	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;
  
  good_area:
  	/* Address space is OK.  Now check access rights. */
  	si_code = SEGV_ACCERR;
  
  	switch (cause) {
  	case FLT_IFETCH:
  		if (!(vma->vm_flags & VM_EXEC))
  			goto bad_area;
  		break;
  	case FLT_LOAD:
  		if (!(vma->vm_flags & VM_READ))
  			goto bad_area;
  		break;
  	case FLT_STORE:
  		if (!(vma->vm_flags & VM_WRITE))
  			goto bad_area;
  		flags |= FAULT_FLAG_WRITE;
  		break;
  	}
  
  	fault = handle_mm_fault(vma, address, flags);
  
  	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
  		return;
  
  	/* The most common case -- we are done. */
  	if (likely(!(fault & VM_FAULT_ERROR))) {
  		if (flags & FAULT_FLAG_ALLOW_RETRY) {
  			if (fault & VM_FAULT_MAJOR)
  				current->maj_flt++;
  			else
  				current->min_flt++;
  			if (fault & VM_FAULT_RETRY) {
  				flags &= ~FAULT_FLAG_ALLOW_RETRY;
  				flags |= FAULT_FLAG_TRIED;
  				goto retry;
  			}
  		}
  
  		up_read(&mm->mmap_sem);
  		return;
  	}
  
  	up_read(&mm->mmap_sem);
  
  	/* Handle copyin/out exception cases */
  	if (!user_mode(regs))
  		goto no_context;
  
  	if (fault & VM_FAULT_OOM) {
  		pagefault_out_of_memory();
  		return;
  	}
  
  	/* User-mode address is in the memory map, but we are
  	 * unable to fix up the page fault.
  	 */
  	if (fault & VM_FAULT_SIGBUS) {
  		si_signo = SIGBUS;
  		si_code = BUS_ADRERR;
  	}
  	/* Address is not in the memory map */
  	else {
  		si_signo = SIGSEGV;
  		si_code  = SEGV_ACCERR;
  	}
  	force_sig_fault(si_signo, si_code, (void __user *)address, current);
  	return;
  
  bad_area:
  	up_read(&mm->mmap_sem);
  
  	if (user_mode(regs)) {
  		force_sig_fault(SIGSEGV, si_code, (void __user *)address, current);
  		return;
  	}
  	/* Kernel-mode fault falls through */
  
  no_context:
  	fixup = search_exception_tables(pt_elr(regs));
  	if (fixup) {
  		pt_set_elr(regs, fixup->fixup);
  		return;
  	}
  
  	/* Things are looking very, very bad now */
  	bust_spinlocks(1);
  	printk(KERN_EMERG "Unable to handle kernel paging request at "
  		"virtual address 0x%08lx, regs %p\n", address, regs);
  	die("Bad Kernel VA", regs, SIGKILL);
  }
  
  
  void read_protection_fault(struct pt_regs *regs)
  {
  	unsigned long badvadr = pt_badva(regs);
  
  	do_page_fault(badvadr, FLT_LOAD, regs);
  }
  
  void write_protection_fault(struct pt_regs *regs)
  {
  	unsigned long badvadr = pt_badva(regs);
  
  	do_page_fault(badvadr, FLT_STORE, regs);
  }
  
  void execute_protection_fault(struct pt_regs *regs)
  {
  	unsigned long badvadr = pt_badva(regs);
  
  	do_page_fault(badvadr, FLT_IFETCH, regs);
  }
  