* Re: [PATCH 1/5] lib: Add a generic version of devmem_is_allowed()
[not found] ` <20200709200552.1910298-2-palmer@dabbelt.com>
@ 2020-07-09 20:49 ` Mike Rapoport
2020-07-09 20:54 ` Palmer Dabbelt
0 siblings, 1 reply; 2+ messages in thread
From: Mike Rapoport @ 2020-07-09 20:49 UTC (permalink / raw)
To: Palmer Dabbelt
Cc: mark.rutland, steve, davidgow, catalin.marinas, linus.walleij,
Palmer Dabbelt, elver, glider, willy, zong.li, mchehab+samsung,
linux-riscv, alex.shi, will, dan.j.williams, linux-arch, uwe,
alex, takahiro.akashi, paulmck, masahiroy, linux, krzk, ardb,
bgolaszewski, kernel-team, pmladek, zaslonko, aou, keescook,
Arnd Bergmann, rostedt, broonie, matti.vaittinen, gregory.0xf0,
Paul Walmsley, tglx, andriy.shevchenko, gxt, linux-arm-kernel,
rdunlap, Nick Desaulniers, linux-kernel, mcgrof, james.morse,
mhiramat, akpm, davem
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.
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.
> 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
>
--
Sincerely yours,
Mike.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH 1/5] lib: Add a generic version of devmem_is_allowed()
2020-07-09 20:49 ` [PATCH 1/5] lib: Add a generic version of devmem_is_allowed() Mike Rapoport
@ 2020-07-09 20:54 ` Palmer Dabbelt
0 siblings, 0 replies; 2+ messages in thread
From: Palmer Dabbelt @ 2020-07-09 20:54 UTC (permalink / raw)
To: rppt
Cc: mark.rutland, steve, davidgow, catalin.marinas, linus.walleij,
elver, glider, willy, zong.li, mchehab+samsung, linux-riscv,
alex.shi, will, dan.j.williams, linux-arch, uwe, alex,
takahiro.akashi, paulmck, masahiroy, linux, krzk, ardb,
bgolaszewski, kernel-team, pmladek, zaslonko, aou, keescook,
Arnd Bergmann, rostedt, broonie, matti.vaittinen, gregory.0xf0,
Paul Walmsley, tglx, andriy.shevchenko, gxt, linux-arm-kernel,
rdunlap, Nick Desaulniers, linux-kernel, mcgrof, james.morse,
mhiramat, akpm, davem
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
>>
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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[not found] <20200709200552.1910298-1-palmer@dabbelt.com>
[not found] ` <20200709200552.1910298-2-palmer@dabbelt.com>
2020-07-09 20:49 ` [PATCH 1/5] lib: Add a generic version of devmem_is_allowed() Mike Rapoport
2020-07-09 20:54 ` Palmer Dabbelt
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