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- // 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>
- /*
- * 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;
- }
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