linux/arch/arm64/kernel/sys_compat.c

/*
 * 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/unistd.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;
	}
}