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 <[email protected]>
---
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;
--
2.27.0
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 <[email protected]>
> ---
> 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
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.
On Tue, Jun 16, 2020 at 8:27 PM Nick Kossifidis <[email protected]> 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 <[email protected]>
> > ---
> > 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?
Στις 2020-06-17 04:56, Zong Li έγραψε:
> On Tue, Jun 16, 2020 at 8:27 PM Nick Kossifidis <[email protected]>
> 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 <[email protected]>
>> > ---
>> > 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 ?
On Wed, Jun 17, 2020 at 1:28 PM Nick Kossifidis <[email protected]> wrote:
>
> Στις 2020-06-17 04:56, Zong Li έγραψε:
> > On Tue, Jun 16, 2020 at 8:27 PM Nick Kossifidis <[email protected]>
> > 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 <[email protected]>
> >> > ---
> >> > 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 ?
It's OK to me, It seems to me that exclusive is more suitable than
busy when initialization.
On Tue, 16 Jun 2020 00:45:47 PDT (-0700), [email protected] wrote:
> 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.
In fact, it's exactly the same (down to a few words of the comment) to the
others that I checked. I'm going to put a generic version in lib/ instead,
I've sent out the patches.
> 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 <[email protected]>
> ---
> 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;
On Fri, Jul 10, 2020 at 4:08 AM Palmer Dabbelt <[email protected]> wrote:
>
> On Tue, 16 Jun 2020 00:45:47 PDT (-0700), [email protected] wrote:
> > 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.
>
> In fact, it's exactly the same (down to a few words of the comment) to the
> others that I checked. I'm going to put a generic version in lib/ instead,
> I've sent out the patches.
>
OK, no problem, thanks for improving it.
> > 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 <[email protected]>
> > ---
> > 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;