Messages in this thread |  | | From | Zong Li <> | Date | Fri, 10 Jul 2020 10:43:42 +0800 | Subject | Re: [PATCH 2/2] riscv: Support CONFIG_STRICT_DEVMEM |
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On Fri, Jul 10, 2020 at 4:08 AM Palmer Dabbelt <palmer@dabbelt.com> wrote: > > On Tue, 16 Jun 2020 00:45:47 PDT (-0700), zong.li@sifive.com 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 <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;
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