Messages in this thread | | | From | Zong Li <> | Date | Wed, 17 Jun 2020 14:32:51 +0800 | Subject | Re: [PATCH 2/2] riscv: Support CONFIG_STRICT_DEVMEM |
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On Wed, Jun 17, 2020 at 1:28 PM Nick Kossifidis <mick@ics.forth.gr> wrote: > > Στις 2020-06-17 04:56, Zong Li έγραψε: > > On Tue, Jun 16, 2020 at 8:27 PM Nick Kossifidis <mick@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.li@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 ?
It's OK to me, It seems to me that exclusive is more suitable than busy when initialization.
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