From 527701eda5f196588df9b36a30651804fea7d1a7 Mon Sep 17 00:00:00 2001 From: Palmer Dabbelt Date: Thu, 9 Jul 2020 11:43:21 -0700 Subject: 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 Signed-off-by: Palmer Dabbelt --- lib/Kconfig | 3 +++ lib/Kconfig.debug | 2 +- lib/Makefile | 2 ++ lib/devmem_is_allowed.c | 27 +++++++++++++++++++++++++++ 4 files changed, 33 insertions(+), 1 deletion(-) create mode 100644 lib/devmem_is_allowed.c (limited to 'lib') diff --git a/lib/Kconfig b/lib/Kconfig index b4b98a03ff98..b26721cf51bc 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -681,6 +681,9 @@ 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 0c781f912f9f..87410f62b501 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1626,7 +1626,7 @@ 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 a4a4c6864f51..34011a11fbb3 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -348,3 +348,5 @@ obj-$(CONFIG_PLDMFW) += pldmfw/ obj-$(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 +#include + +/* + * 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; +} -- cgit v1.2.3