diff options
author | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-07-09 21:43:21 +0300 |
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committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-12-11 23:28:08 +0300 |
commit | 527701eda5f196588df9b36a30651804fea7d1a7 (patch) | |
tree | d9afe5b4753aa0ca2ee1829072ead75c153e369b /lib/devmem_is_allowed.c | |
parent | bbf5c979011a099af5dc76498918ed7df445635b (diff) | |
download | linux-527701eda5f196588df9b36a30651804fea7d1a7.tar.xz |
lib: Add a generic version of devmem_is_allowed()
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>
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; +} |