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As part of adding support for STRICT_DEVMEM to the RISC-V port, Zong provided a devmem_is_allowed() implementation that's exactly the same as all the others I checked. Instead I'm adding a generic version, which will soon be used. Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
28 lines
687 B
C
28 lines
687 B
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* A generic version of devmem_is_allowed.
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*
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* Based on arch/arm64/mm/mmap.c
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*
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* Copyright (C) 2020 Google, Inc.
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* Copyright (C) 2012 ARM Ltd.
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*/
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#include <linux/mm.h>
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#include <linux/ioport.h>
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/*
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* devmem_is_allowed() checks to see if /dev/mem access to a certain address
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* is valid. The argument is a physical page number. We mimic x86 here by
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* disallowing access to system RAM as well as device-exclusive MMIO regions.
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* This effectively disable read()/write() on /dev/mem.
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*/
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int devmem_is_allowed(unsigned long pfn)
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{
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if (iomem_is_exclusive(pfn << PAGE_SHIFT))
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return 0;
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if (!page_is_ram(pfn))
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return 1;
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return 0;
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}
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