Re: [PATCH 2/2] target/arm: Look up ARMCPRegInfo at runtime

[Peter Maydell]

On Fri, 6 Jan 2023 at 19:45, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Do not encode the pointer as a constant in the opcode stream.
> This pointer is specific to the cpu that first generated the
> translation, which runs into problems with both hot-pluggable
> cpus and user-only threads, as cpus are removed.
>
> Perform the lookup in either helper_access_check_cp_reg,
> or a new helper_lookup_cp_reg.

As well as the use-after-free, this is also a correctness
bug, isn't it? If we hardwire in the cpregs pointer for
CPU 0 into the TB, and then CPU 1 with a slightly different
config executes the TB, it will get the cpregs of CPU 0,
not its own, so it might see a register it should not or
vice-versa.

So I think we need this patch anyway, even if we're going
to try to do something to improve sharing of cpreg hashtables
across CPUs.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM