Re: [PATCH 3/3] linux-user/arm: Implement __kernel_cmpxchg64 with host atomics

[Peter Maydell]

On Mon, 14 Mar 2022 at 04:46, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> If CONFIG_ATOMIC64, we can use a host cmpxchg and provide
> atomicity across processes; otherwise we have no choice but
> to continue using start/end_exclusive.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

> -segv:
> -    end_exclusive();
> -    /* We get the PC of the entry address - which is as good as anything,
> -       on a real kernel what you get depends on which mode it uses. */

This comment about the PC the guest signal handler is going
to see when we take the SEGV is still valid, I think ?

> -    /* XXX: check env->error_code */
> -    force_sig_fault(TARGET_SIGSEGV, TARGET_SEGV_MAPERR,
> -                    env->exception.vaddress);
> + segv:
> +    force_sig_fault(TARGET_SIGSEGV,
> +                    page_get_flags(addr) & PAGE_VALID ?
> +                    TARGET_SEGV_ACCERR : TARGET_SEGV_MAPERR, addr);
>  }

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

thanks
-- PMM