[llvm-dev] Dynamic VMA in Sanitizers for AArch64

[Yury Gribov via llvm-dev]

On 09/25/2015 01:27 PM, Yury Gribov wrote:
> On 09/25/2015 11:53 AM, Jakub Jelinek via llvm-dev wrote:
>> On Fri, Sep 25, 2015 at 01:19:48AM -0700, Renato Golin wrote:
>>> After long talks with lots of people, I think we have a winning
>>> strategy to deal with the variable nature of VMA address in AArch64.
>>> It seems that the best way forward is to try the dynamic calculation
>>> at runtime, evaluate the performance, and then, only if the hit is too
>>> great, think about compile-time alternatives. I'd like to know if
>>> everyone is in agreement, so we could get cracking.
>>
>> You mean you want a dynamic shadow offset on aarch64 as opposed to
>> fixed kAArch64_ShadowOffset64 (1UL << 36) one?
>> I think this is completely unnecessary, all you need to change is
>> libsanitizer internals IMNSHO, all that is needed is to make runtime
>> decisions during libasan initialization on the memory layout, and
>> also (because 39 bit VMA is too slow), dynamic decision whether to use
>> 32-bit or 64-bit allocator.  See
>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64435
>> for details.
>
> Added kcc.
>
> FYI optional dynamic offset would also help in not-so-rare situations
> when ASan's shadow range is stolen by early constructors in unsanitized
> libraries.

And - we'll finally be able to run ASan under Valgrind)