diff options
author | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-12-11 12:30:26 -0800 |
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committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-12-11 12:30:26 -0800 |
commit | 7d95a88f9254b711a3a95106fc73f6a3a9866a40 (patch) | |
tree | 9c4551d7f2dce744bbefc359b941fd144f66333d /lib/devmem_is_allowed.c | |
parent | 3ae9c3cde51abcb777125cfcf74cc402f4d0a4c7 (diff) | |
parent | 6585bd827407f55ee30a782492208bfaf4f52feb (diff) |
Add and use a generic version of devmem_is_allowed()
As part of adding STRICT_DEVMEM support to the RISC-V port, Zong provided an
implementation of devmem_is_allowed() that's exactly the same as the version in
a handful of other ports. Rather than duplicate code, I've put a generic
version of this in lib/ and used it for the RISC-V port.
* palmer/generic-devmem:
arm64: Use the generic devmem_is_allowed()
arm: Use the generic devmem_is_allowed()
RISC-V: Use the new generic devmem_is_allowed()
lib: Add a generic version of devmem_is_allowed()
Diffstat (limited to 'lib/devmem_is_allowed.c')
-rw-r--r-- | lib/devmem_is_allowed.c | 27 |
1 files changed, 27 insertions, 0 deletions
diff --git a/lib/devmem_is_allowed.c b/lib/devmem_is_allowed.c new file mode 100644 index 000000000000..c0d67c541849 --- /dev/null +++ b/lib/devmem_is_allowed.c @@ -0,0 +1,27 @@ +// 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 << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} |