Re: [Qemu-trivial] [PATCH 1/1] tci: eliminate UB due to unaligned reads

[Anatoly Trosinenko]

Can rewriting TCI in such a way that every operation is aligned at 4- or even 8-byte boundary fix the situation or are there some more serious problems?

2018-03-03 16:57 GMT+03:00 Richard Henderson <address@hidden>:

On 03/03/2018 12:54 AM, Anatoly Trosinenko wrote:
> Ping.
> Patchwork link: http://patchwork.ozlabs.org/patch/866732/
> <http://patchwork.ozlabs.org/patch/866732/>
> Patchew link:
> http://patchew.org/QEMU/20180127134908.24095-1-address@hidden/
> <http://patchew.org/QEMU/20180127134908.24095-1-address@hidden/>
>
> The code in tcg/tci.c reads some data from TCI bytecode through
> pointer dereferencing. As far as I know unaligned reads in such a way are
> undefined behavior and compiling with -fsanitize=undefined enumerated
> them as such at run-time.

This is exactly one of the reasons why I have urged for TCI to be abandoned.

While your patch works, it is *enormously* inefficient for hosts that require it.


r~

--

С уважением,
Анатолий Тросиненко
e-mail: address@hidden