Messages in this thread |  | | Date | Tue, 16 Jun 2020 15:27:36 +0300 | From | Nick Kossifidis <> | Subject | Re: [PATCH 2/2] riscv: Support CONFIG_STRICT_DEVMEM |
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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 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.
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