text: /*
   * Based on arch/arm/kernel/sys_arm.c
   *
   * Copyright (C) People who wrote linux/arch/i386/kernel/sys_i386.c
   * Copyright (C) 1995, 1996 Russell King.
   * Copyright (C) 2012 ARM Ltd.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
   */
  
  #include <linux/compat.h>
  #include <linux/personality.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/syscalls.h>
  #include <linux/uaccess.h>
  
  #include <asm/cacheflush.h>
  #include <asm/unistd32.h>
  
  static inline void
  do_compat_cache_op(unsigned long start, unsigned long end, int flags)
  {
  	struct mm_struct *mm = current->active_mm;
  	struct vm_area_struct *vma;
  
  	if (end < start || flags)
  		return;
  
  	down_read(&mm->mmap_sem);
  	vma = find_vma(mm, start);
  	if (vma && vma->vm_start < end) {
  		if (start < vma->vm_start)
  			start = vma->vm_start;
  		if (end > vma->vm_end)
  			end = vma->vm_end;
  		up_read(&mm->mmap_sem);
  		__flush_cache_user_range(start & PAGE_MASK, PAGE_ALIGN(end));
  		return;
  	}
  	up_read(&mm->mmap_sem);
  }
  
  /*
   * Handle all unrecognised system calls.
   */
  long compat_arm_syscall(struct pt_regs *regs)
  {
  	unsigned int no = regs->regs[7];
  
  	switch (no) {
  	/*
  	 * Flush a region from virtual address 'r0' to virtual address 'r1'
  	 * _exclusive_.  There is no alignment requirement on either address;
  	 * user space does not need to know the hardware cache layout.
  	 *
  	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
  	 * is defined to be something else.  For now we ignore it, but may
  	 * the fires of hell burn in your belly if you break this rule. ;)
  	 *
  	 * (at a later date, we may want to allow this call to not flush
  	 * various aspects of the cache.  Passing '0' will guarantee that
  	 * everything necessary gets flushed to maintain consistency in
  	 * the specified region).
  	 */
  	case __ARM_NR_compat_cacheflush:
  		do_compat_cache_op(regs->regs[0], regs->regs[1], regs->regs[2]);
  		return 0;
  
  	case __ARM_NR_compat_set_tls:
  		current->thread.tp_value = regs->regs[0];
  
  		/*
  		 * Protect against register corruption from context switch.
  		 * See comment in tls_thread_flush.
  		 */
  		barrier();
  		asm ("msr tpidrro_el0, %0" : : "r" (regs->regs[0]));
  		return 0;
  
  	default:
  		return -ENOSYS;
  	}
  }
  