Στις 2020-06-17 04:56, Zong Li έγραψε:
On Tue, Jun 16, 2020 at 8:27 PM Nick Kossifidis <m...@ics.forth.gr>
wrote:
Στις 2020-06-16 10:45, Zong Li έγραψε:
> Implement the 'devmem_is_allowed()' interface for RISC-V, like some of
> other architectures have done. It will be called from
> range_is_allowed()
> when userpsace attempts to access /dev/mem.
>
> Access to exclusive IOMEM and kernel RAM is denied unless
> CONFIG_STRICT_DEVMEM is set to 'n'.
>
> Test it by devmem, the result as follows:
>
> - CONFIG_STRICT_DEVMEM=y
> $ devmem 0x10010000
> 0x00000000
> $ devmem 0x80200000
> 0x0000106F
>
> - CONFIG_STRICT_DEVMEM is not set
> $ devmem 0x10010000
> devmem: mmap: Operation not permitted
> $ devmem 0x80200000
> devmem: mmap: Operation not permitted
>
> Signed-off-by: Zong Li <zong...@sifive.com>
> ---
> arch/riscv/Kconfig | 1 +
> arch/riscv/include/asm/io.h | 2 ++
> arch/riscv/mm/init.c | 19 +++++++++++++++++++
> 3 files changed, 22 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 128192e14ff2..ffd7841ede4c 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -16,6 +16,7 @@ config RISCV
> select ARCH_HAS_BINFMT_FLAT
> select ARCH_HAS_DEBUG_VIRTUAL if MMU
> select ARCH_HAS_DEBUG_WX
> + select ARCH_HAS_DEVMEM_IS_ALLOWED
> select ARCH_HAS_GCOV_PROFILE_ALL
> select ARCH_HAS_GIGANTIC_PAGE
> select ARCH_HAS_MMIOWB
> diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h
> index 3835c3295dc5..04ac65ab93ce 100644
> --- a/arch/riscv/include/asm/io.h
> +++ b/arch/riscv/include/asm/io.h
> @@ -147,4 +147,6 @@ __io_writes_outs(outs, u64, q, __io_pbr(),
> __io_paw())
>
> #include <asm-generic/io.h>
>
> +extern int devmem_is_allowed(unsigned long pfn);
> +
> #endif /* _ASM_RISCV_IO_H */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index bbe816e03b2f..5e7e61519acc 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -517,6 +517,25 @@ void mark_rodata_ro(void)
> }
> #endif
>
> +#ifdef CONFIG_STRICT_DEVMEM
> +#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.
> + *
> + * Disallow 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;
> +}
> +#endif
> +
> void __init resource_init(void)
> {
> struct memblock_region *region;
This shouldn't be part of /mm/init.c, it has nothing to do with memory
initialization, I suggest we move it to another file like mmap.c on
Let me move it, thanks.
arm/arm64. Also before using iomem_is_exclusive we should probably
also
mark any reserved regions with the no-map attribute as busy|exclusive,
reserved-memory regions are not necessarily part of the main memory so
the page_is_ram check may pass and iomem_is_exclusive won't do any
good.
What do you think if we mark the reserved region in
kdump_resource_init, and change the kdump_resource_init to a more
generic name for initializing resources?
Sounds good to me, I'll work on this within the week. Do you agree with
marking the no-map reserved-memory regions as exclusive ?
