| 1 | // SPDX-License-Identifier: GPL-2.0-only |
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| 2 | /* |
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| 3 | * A generic version of devmem_is_allowed. |
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| 4 | * |
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| 5 | * Based on arch/arm64/mm/mmap.c |
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| 6 | * |
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| 7 | * Copyright (C) 2020 Google, Inc. |
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| 8 | * Copyright (C) 2012 ARM Ltd. |
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| 9 | */ |
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| 10 | |
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| 11 | #include <linux/mm.h> |
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| 12 | #include <linux/ioport.h> |
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| 13 | #include <linux/io.h> |
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| 14 | |
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| 15 | /* |
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| 16 | * devmem_is_allowed() checks to see if /dev/mem access to a certain address |
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| 17 | * is valid. The argument is a physical page number. We mimic x86 here by |
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| 18 | * disallowing access to system RAM as well as device-exclusive MMIO regions. |
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| 19 | * This effectively disable read()/write() on /dev/mem. |
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| 20 | */ |
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| 21 | int devmem_is_allowed(unsigned long pfn) |
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| 22 | { |
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| 23 | if (iomem_is_exclusive(PFN_PHYS(pfn))) |
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| 24 | return 0; |
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| 25 | if (!page_is_ram(pfn)) |
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| 26 | return 1; |
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| 27 | return 0; |
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| 28 | } |
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| 29 | |
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