On Mon, Oct 29, 2018 at 10:38:11AM -0500, Bill Seurer wrote:
> > I'm still wondering what didn't work with 41 bits? AFAICS, due to
> > highshadow=highmem-offset and lowshadow=low+offset, and the existence of a
> > non-empty shadow-gap, offset must be minimum(vbits)-3 (vbits being one of
> > the above numbers). Why would 41 not work for the other vbit setting?
> > It would lead to a large shadow gap, but so? If a shadow-gap isn't
> > necessary then minimum(vbits)-2 would also work.
>
> 41 was what the value previously was and it did not work (IIRC with 47 bit
> VMA kernels which were "new" at the time) thus the change.
What we'd like to see is details or URL with those why it didn't work with
47 bit. E.g. x86_64 uses much lower shadow offset (0x7fff8000), asan has
support for multiple shadow areas, gaps and normal areas.
I think ppc64 binaries are usually using 0x10000000 base, so that isn't a
problem, so is there a conflict with the default dynamic linker placement or
default placement of shared libraries when using the 47-bit VMA?
What do you get with the 41-bit shadow offset and ASAN_OPTIONS=verbosity=1
on 47-bit VMA that e.g. kMidMemBeg/kMidMemEnd couldn't solve?
Jakub
