On 11/18/2016 11:05 AM, Mark Rutland wrote:
> On Fri, Nov 18, 2016 at 10:42:56AM -0800, Laura Abbott wrote:
>> On 11/18/2016 09:53 AM, Mark Rutland wrote:
>>> On Thu, Nov 17, 2016 at 05:16:56PM -0800, Laura Abbott wrote:
>
>>>> +#define __virt_to_phys_nodebug(x) ({ \
>>>> phys_addr_t __x = (phys_addr_t)(x); \
>>>> - __x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET : \
>>>> - (__x - kimage_voffset); })
>>>> + ((__x & ~PAGE_OFFSET) + PHYS_OFFSET); \
>>>> +})
>>>
>>> Given the KASAN failure, and the strong possibility that there's even
>>> more stuff lurking in common code, I think we should retain the logic to
>>> handle kernel image addresses for the timebeing (as x86 does). Once
>>> we've merged DEBUG_VIRTUAL, it will be easier to track those down.
>>
>> Agreed. I might see about adding another option DEBUG_STRICT_VIRTUAL
>> for catching bad __pa vs __pa_symbol usage and keep DEBUG_VIRTUAL for
>> catching addresses that will work in neither case.
>
> I think it makes sense for DEBUG_VIRTUAL to do both, so long as the
> default behaviour (and fallback after a WARN for virt_to_phys()) matches
> what we currently do. We'll get useful diagnostics, but a graceful
> fallback.
>
I was suggesting making the WARN optional for having this be more useful
before all the __pa_symbol stuff gets cleaned up. Maybe the WARN won't
actually be a hindrance.
Thanks,
Laura
> I think the helpers I suggested below do that? Or have I misunderstood,
> and you mean something stricter (e.g. checking whether a lm address is
> is backed by something)?
>
>>> phys_addr_t __virt_to_phys(unsigned long x)
>>> {
>>> WARN(!__is_lm_address(x),
>>> "virt_to_phys() used for non-linear address: %pK\n",
>>> (void*)x);
>>>
>>> return __virt_to_phys_nodebug(x);
>>> }
>>> EXPORT_SYMBOL(__virt_to_phys);
>
>>> phys_addr_t __phys_addr_symbol(unsigned long x)
>>> {
>>> /*
>>> * This is bounds checking against the kernel image only.
>>> * __pa_symbol should only be used on kernel symbol addresses.
>>> */
>>> VIRTUAL_BUG_ON(x < (unsigned long) KERNEL_START ||
>>> x > (unsigned long) KERNEL_END);
>>>
>>> return __pa_symbol_nodebug(x);
>>> }
>>> EXPORT_SYMBOL(__phys_addr_symbol);
>
> Thanks,
> Mark.
>
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