[thirdparty/linux.git] / lib / devmem_is_allowed.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * A generic version of devmem_is_allowed.
 *
 * Based on arch/arm64/mm/mmap.c
 *
 * Copyright (C) 2020 Google, Inc.
 * Copyright (C) 2012 ARM Ltd.
 */

#include <linux/mm.h>
#include <linux/ioport.h>
#include <linux/io.h>

/*
 * devmem_is_allowed() checks to see if /dev/mem access to a certain address
 * is valid. The argument is a physical page number.  We mimic x86 here by
 * disallowing access to system RAM as well as device-exclusive MMIO regions.
 * This effectively disable read()/write() on /dev/mem.
 */
int devmem_is_allowed(unsigned long pfn)
{
	if (iomem_is_exclusive(PFN_PHYS(pfn)))
		return 0;
	if (!page_is_ram(pfn))
		return 1;
	return 0;
}
Commit	Line	Data
527701ed PD	1	// SPDX-License-Identifier: GPL-2.0-only
	2	/*
	3	* A generic version of devmem_is_allowed.
	4	*
	5	* Based on arch/arm64/mm/mmap.c
	6	*
	7	* Copyright (C) 2020 Google, Inc.
	8	* Copyright (C) 2012 ARM Ltd.
	9	*/
	10
	11	#include <linux/mm.h>
	12	#include <linux/ioport.h>
6b76ca2a	13	#include <linux/io.h>
527701ed PD	14
	15	/*
	16	* devmem_is_allowed() checks to see if /dev/mem access to a certain address
	17	* is valid. The argument is a physical page number. We mimic x86 here by
	18	* disallowing access to system RAM as well as device-exclusive MMIO regions.
	19	* This effectively disable read()/write() on /dev/mem.
	20	*/
	21	int devmem_is_allowed(unsigned long pfn)
	22	{
854f3264	23	if (iomem_is_exclusive(PFN_PHYS(pfn)))
527701ed PD	24	return 0;
	25	if (!page_is_ram(pfn))
	26	return 1;
	27	return 0;
	28	}