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 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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