Re: [PATCH v4 2/4] target/arm: Make sure that commpage's tb->size != 0

[Peter Maydell]

On Thu, 15 Apr 2021 at 14:03, Ilya Leoshkevich <iii@linux.ibm.com> wrote:
>
> tb_gen_code() assumes that tb->size must never be zero, otherwise it
> may produce spurious exceptions. For ARM this may happen when creating
> a translation block for the commpage.
>
> Fix by pretending that commpage translation blocks have at least one
> instruction.
>
> Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> ---
>  target/arm/translate.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/target/arm/translate.c b/target/arm/translate.c
> index 62b1c2081b..885f69b044 100644
> --- a/target/arm/translate.c
> +++ b/target/arm/translate.c
> @@ -9060,6 +9060,7 @@ static void arm_tr_translate_insn(DisasContextBase 
> *dcbase, CPUState *cpu)
>      unsigned int insn;
>
>      if (arm_pre_translate_insn(dc)) {
> +        dc->base.pc_next += 4;
>          return;
>      }

Why does the call to arm_pre_translate_insn() in arm_tr_translate_insn() need
this change but not the one in thumb_tr_translate_insn() ?

thanks
-- PMM