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authorPalmer Dabbelt <palmerdabbelt@google.com>2020-07-09 21:43:21 +0300
committerPalmer Dabbelt <palmerdabbelt@google.com>2020-12-11 23:28:08 +0300
commit527701eda5f196588df9b36a30651804fea7d1a7 (patch)
treed9afe5b4753aa0ca2ee1829072ead75c153e369b /lib/devmem_is_allowed.c
parentbbf5c979011a099af5dc76498918ed7df445635b (diff)
downloadlinux-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.c27
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;
+}