Messages in this thread |  | | Date | Thu, 09 Jul 2020 13:54:33 -0700 (PDT) | Subject | Re: [PATCH 1/5] lib: Add a generic version of devmem_is_allowed() | From | Palmer Dabbelt <> |
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On Thu, 09 Jul 2020 13:49:21 PDT (-0700), rppt@linux.ibm.com wrote: > Hi Palmer, > > On Thu, Jul 09, 2020 at 01:05:48PM -0700, Palmer Dabbelt wrote: >> From: Palmer Dabbelt <palmerdabbelt@google.com> >> >> 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. >> >> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com> >> --- >> include/asm-generic/io.h | 4 ++++ >> lib/Kconfig | 4 ++++ >> lib/Makefile | 2 ++ >> lib/devmem_is_allowed.c | 27 +++++++++++++++++++++++++++ >> 4 files changed, 37 insertions(+) >> create mode 100644 lib/devmem_is_allowed.c >> >> diff --git a/include/asm-generic/io.h b/include/asm-generic/io.h >> index 8b1e020e9a03..69e3db65fba0 100644 >> --- a/include/asm-generic/io.h >> +++ b/include/asm-generic/io.h >> @@ -1122,6 +1122,10 @@ static inline void memcpy_toio(volatile void __iomem *addr, const void *buffer, >> } >> #endif >> >> +#ifndef CONFIG_GENERIC_DEVMEM_IS_ALLOWED >> +extern int devmem_is_allowed(unsigned long pfn); >> +#endif >> + >> #endif /* __KERNEL__ */ >> >> #endif /* __ASM_GENERIC_IO_H */ >> diff --git a/lib/Kconfig b/lib/Kconfig >> index df3f3da95990..3b1b6481e073 100644 >> --- a/lib/Kconfig >> +++ b/lib/Kconfig >> @@ -676,3 +676,7 @@ config GENERIC_LIB_CMPDI2 >> >> config GENERIC_LIB_UCMPDI2 >> bool >> + >> +config GENERIC_LIB_DEVMEM_IS_ALLOWED >> + bool >> + select ARCH_HAS_DEVMEM_IS_ALLOWED > > This seems to work the other way around from the usual Kconfig chains. > In the most cases ARCH_HAS_SOMETHING selects GENERIC_SOMETHING.
Ya, it seemed kind of odd.
> > I believe nicer way would be to make > > config STRICT_DEVMEM > bool "Filter access to /dev/mem" > depends on MMU && DEVMEM > depends on ARCH_HAS_DEVMEM_IS_ALLOWED || GENERIC_LIB_DEVMEM_IS_ALLOWED > > config GENERIC_LIB_DEVMEM_IS_ALLOWED > bool > > and then s/select ARCH_HAS_DEVMEM_IS_ALLOWED/select GENERIC_LIB_DEVMEM_IS_ALLOWED/ > in the arch Kconfigs and drop ARCH_HAS_DEVMEM_IS_ALLOWED in the end.
There's some arches that can't be converted to the generic version, at least not trivially, so we wouldn't drop it. I think it's still cleaner, though. I'll send a v2.
> >> diff --git a/lib/Makefile b/lib/Makefile >> index b1c42c10073b..554ef14f9be5 100644 >> --- a/lib/Makefile >> +++ b/lib/Makefile >> @@ -318,3 +318,5 @@ obj-$(CONFIG_OBJAGG) += objagg.o >> # KUnit tests >> obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o >> obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o >> + >> +obj-$(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; >> +} >> -- >> 2.27.0.383.g050319c2ae-goog >>
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