Messages in this thread |  | | Date | Wed, 17 Jun 2020 08:28:17 +0300 | From | Nick Kossifidis <> | Subject | Re: [PATCH 2/2] riscv: Support CONFIG_STRICT_DEVMEM |
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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 ?
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