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authorPalmer Dabbelt <palmerdabbelt@google.com>2020-12-11 12:30:26 -0800
committerPalmer Dabbelt <palmerdabbelt@google.com>2020-12-11 12:30:26 -0800
commit7d95a88f9254b711a3a95106fc73f6a3a9866a40 (patch)
tree9c4551d7f2dce744bbefc359b941fd144f66333d /lib
parent3ae9c3cde51abcb777125cfcf74cc402f4d0a4c7 (diff)
parent6585bd827407f55ee30a782492208bfaf4f52feb (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')
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Kconfig.debug2
-rw-r--r--lib/Makefile2
-rw-r--r--lib/devmem_is_allowed.c27
4 files changed, 33 insertions, 1 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index b46a9fd122c8..46806332a8cc 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -686,6 +686,9 @@ config GENERIC_LIB_CMPDI2
config GENERIC_LIB_UCMPDI2
bool
+config GENERIC_LIB_DEVMEM_IS_ALLOWED
+ bool
+
config PLDMFW
bool
default n
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d7a7bc3b6098..c63fc68f9bf2 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1645,7 +1645,7 @@ config ARCH_HAS_DEVMEM_IS_ALLOWED
config STRICT_DEVMEM
bool "Filter access to /dev/mem"
depends on MMU && DEVMEM
- depends on ARCH_HAS_DEVMEM_IS_ALLOWED
+ depends on ARCH_HAS_DEVMEM_IS_ALLOWED || GENERIC_LIB_DEVMEM_IS_ALLOWED
default y if PPC || X86 || ARM64
help
If this option is disabled, you allow userspace (root) access to all
diff --git a/lib/Makefile b/lib/Makefile
index ce45af50983a..431d7d894bf7 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -352,3 +352,5 @@ obj-$(CONFIG_BITFIELD_KUNIT) += bitfield_kunit.o
obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
obj-$(CONFIG_BITS_TEST) += test_bits.o
+
+obj-$(CONFIG_GENERIC_LIB_DEVMEM_IS_ALLOWED) += devmem_is_allowed.o
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;
+}