Messages in this thread |  | | From | Ard Biesheuvel <> | Date | Sat, 29 Oct 2016 09:39:45 +0100 | Subject | Re: [RFC][PATCH] arm64: Add support for CONFIG_DEBUG_VIRTUAL |
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On 28 October 2016 at 23:07, Laura Abbott <labbott@redhat.com> wrote: >>>> diff --git a/arch/arm64/mm/physaddr.c b/arch/arm64/mm/physaddr.c >>>> new file mode 100644 >>>> index 0000000..6c271e2 >>>> --- /dev/null >>>> +++ b/arch/arm64/mm/physaddr.c >>>> @@ -0,0 +1,17 @@ >>>> +#include <linux/mm.h> >>>> + >>>> +#include <asm/memory.h> >>>> + >>>> +unsigned long __virt_to_phys(unsigned long x) >>>> +{ >>>> + phys_addr_t __x = (phys_addr_t)x; >>>> + >>>> + if (__x & BIT(VA_BITS - 1)) { >>>> + /* The bit check ensures this is the right range */ >>>> + return (__x & ~PAGE_OFFSET) + PHYS_OFFSET; >>>> + } else { >>>> + VIRTUAL_BUG_ON(x < kimage_vaddr || x > (unsigned long)_end); >>> >>> >>> IIUC, in (3) you were asking if the last check should be '>' or '>='? >>> >>> To match high_memory, I suspect the latter, as _end doesn't fall within >>> the mapped virtual address space. >>> >> >> I was actually concerned about if _end would be correct with KASLR. >> Ard confirmed that it gets fixed up to be correct. I'll change the >> check to check for >=. >> > > While testing this, I found two places with __pa(_end) to get bounds, > one in arm64 code and one in memblock code. x86 gets away with this > because memblock is actually __pa_symbol and x86 does image placement > different and can check against the maximum image size. I think > including _end in __pa_symbol but excluding it from the generic > __virt_to_phys makes sense. It's a bit nicer than doing _end - 1 + > 1 everywhere. >
Could we redefine __pa_symbol() under CONFIG_DEBUG_VIRTUAL to something that checks (x >= kimage_vaddr + TEXT_OFFSET || x <= (unsigned long)_end), i.e., reject linear virtual addresses? (Assuming my understanding of the meaning of __pa_symbol() is correct)
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